Comparative analysis of Mpox clades: epidemiology, transmission dynamics, and detection strategies

Abstract

Background

Monkeypox (Mpox), a zoonotic disease caused by the monkeypox virus, has gained global attention due to rising incidence and the emergence of new clades. Understanding the epidemiology, transmission dynamics, and diagnostic challenges associated with the two major clades, Clades I and II, is crucial for outbreak preparedness and control.

Methods

This review analyzes Mpox clades, highlighting their geographic distribution, virulence, transmissibility, and diagnostic approaches. It also presents recent outbreaks, diagnostic advancements, vaccination strategies, and critical research gaps in Mpox surveillance and response.

Results

Clade I, primarily in Central Africa, exhibits the highest virulence with a 5–10% case fatality rate. Clade II, which includes subclades IIa, IIb, and the newly identified Clade Ib, demonstrates lower virulence but higher transmissibility beyond endemic regions. Recent outbreaks (2022–2024), driven by Clade IIb, present atypical clinical presentations and emphasize intimate human-to-human contact as a key transmission route. Polymerase chain reaction, next-generation sequencing, and emerging CRISPR-based diagnostics have improved detection, while modified vaccinia Ankara-based vaccines have shown effectiveness despite challenges in equitable distribution.

Conclusions

Addressing critical research gaps, such as clade-specific virulence mechanisms, zoonotic reservoirs, and evolutionary patterns, is essential for improving Mpox surveillance and control. Strengthening genomic surveillance, expanding access to affordable diagnostics, and fostering international collaboration will enhance preparedness for future outbreaks and mitigate the impact of this emerging infectious disease.

Highlights

• Comparison of Mpox virus (MPXV) clades, in geography, virulence, transmission, and clinical outcomes between Clade I, Clade II, and emerging subclades IIb and Ib.

• The epidemiology of Mpox focuses on the 2022–2024 global outbreaks of Clade IIb, marked by unusual clinical presentations and fast human-to-human spread in non-endemic areas.

• Key advancements in diagnostic technologies like PCR, NGS, and CRISPR assays, improving MPXV detection and clade differentiation.

• The effectiveness of MVA-based vaccines against various MPXV clades is presented while highlighting challenges in equitable distribution and region-specific vaccination strategies.

• Emerging Mpox research priorities include genomic surveillance, clade-specific virulence, affordable diagnostics, and overcoming socioeconomic barriers to outbreak management.

Graphical Abstract

Introduction

Mpox, previously called monkeypox, is a zoonotic disease caused by the monkeypox virus (MPXV), a double-stranded DNA virus belonging to the Orthopoxvirus genus of the Poxviridae family. Mpox was first identified in laboratory monkeys in 1958 [1]. However, its significance as a public health concern was only recognised in 1970, when the first human case was reported in the Democratic Republic of Congo [1]. Mpox is one of the recently emerged, geographically localised illnesses that has become a global concern due to increased incidence and shifting epidemiology that allows the disease to continue perpetuating through human-to-human transmission [2]. Mpox causes fever, lymphadenopathy, rash, and dermal lesions. Although Mpox is generally considered less virulent than smallpox, it has challenges, such as a broader host range and atypical presentations in recent outbreaks. The end of vaccination campaigns for smallpox in 1980 left vast segments of the global population exposed to MPXV infections. Declining cross-protection due to waning immunity increases the possibility of outbreaks [3]. Mpox was first recognised as a zoonotic threat, often persisting in central and West African countries, with sporadic outbreaks associated with contact with infected wildlife, including rodents and primates. Its emergence in non-endemic regions worldwide during the 2022–2024 global outbreaks reemphasised its ability to spread internationally. These outbreaks were associated with changes in transmission dynamics, such as sustained human-to-human transmission and an expanded demographic profile of affected populations [4]Understanding the epidemiology and transmission modes of Mpox is vital for global health security. Studying Mpox clades is required to better understand genetic diversity, mode of transmission, and clinical outcomes, which underpin effective prevention and control measures.

The first genomic studies of the virus identified two distinct phylogenetic clades: the Central African clade, or Clade I, and the West African clade, or Clade II. These clades were distinguished by their geographic distribution, virulence, and transmission dynamics [5]. Clade I was more virulent, with a case fatality rate (CFR) between 5 and 10%, which also had a more significant potential for human-to-human transmission. This was in sharp contrast to Clade II, found in the West African areas of Nigeria, Ghana, and Sierra Leone, which presented less severely clinically and with lower CFRs, often less than 3% [6].

Mpox emerged as a significant public health concern early in the twenty-first century following major outbreaks. The 1996–1997 outbreak in the Democratic Republic of Congo (DRC) provided the first evidence of the virus being capable of widespread transmission, with hundreds of cases reported. It was also a period when the campaigns for smallpox vaccination ceased, creating a growing immunity gap that facilitated MPXV transmission [7]. The first significant spread of Mpox outside Africa was the 2003 outbreak in the United States, caused by the importation of infected African rodents, clearly highlighting the dangers of global wildlife trade [8]. Advances in genomic sequencing over the past decade have further defined clades of MPXV, with the identification of Clade IIa and Clade IIb subclades and the more recently characterised Clade Ib. While still endemic to West Africa with poor human-to-human transmission, Clade IIa is more transmissible and adaptable; it has served as the dominant clade within the 2022–2024 global outbreak [9] (Table 1). A new clade Ib has been identified; however, this is still being studied. Such an intermediate lineage of evolution harbours unique genetic markers that could influence its epidemiological and clinical behaviour. Over time, the emergence and diversification of Mpox clades stress the virus's ability to adapt to changing ecological and demographic conditions, further underlining the importance of knowing clade-specific characteristics for global surveillance, diagnostic strategies, and public health interventions [21].

Table 1.

Differences between clade I and clade II of the Mpox virus

Feature	Clade I (Central African)	Clade II (West African)	References
Geographic distribution	Central Africa (e.g., Congo Basin)	West Africa (e.g., Nigeria, Sierra Leone)	[10]
Virulence	High	Moderate to Low	[10, 11]
Case Fatality Rate (CFR)	5–10%	< 3%	[10, 11]
Transmission	Zoonotic and human-to-human	Primarily zoonotic; limited human-to-human (IIa), enhanced in IIb	[12, 13]
Clinical presentation	Severe symptoms, widespread systemic involvement	Mild to moderate symptoms; localised lesions	[3, 4]
Subclades	Not subclassified	IIa and IIb	[14–16]
Role in outbreaks	Localised, rural outbreaks	IIb linked to global outbreaks (2022–2024)	[17]
Reservoirs	Rodents, primates	Similar reservoirs (e.g., rodents)	[13, 18]
Diagnostic challenges	Severe cases prompt clinical suspicion	Atypical presentations complicate diagnosis (IIb)	[15, 17]
Vaccine effectiveness	High (using MVA-based vaccines)	High, but potential antigenic drift in IIb	[19, 20]

Classification of Mpox clades

Description of clade I and clade II

Clade I and Clade II of Mpox (monkeypox) are distinct genetic lineages of the virus (Fig. 1). Clade I, primarily found in Central Africa, has a higher fatality rate. Clade II, which emerged in West Africa, is responsible for the most recent global outbreaks and tends to cause milder disease. The classification is important for understanding transmission patterns, disease severity, and vaccine development strategies [7–14, 21].

Fig. 1.

Comparative severity and transmission of clade I vs. clade II

Subclassification: clade IIa, IIb, Ia, and the newly identified clade Ib

Advancements in genomic sequencing and phylogenetic analysis have enabled the sub-classification of Clade II, which further splits into Clade IIa, Clade IIb, and newly identified Clade Ib. All these subclades have varied genetic characteristics and epidemiological behaviours and reflect the evolutionary history of MPXV as it evolves under environmental pressure and host interactions [22].

Clade IIa is a relic of ancestral lineage within Clade II and has remained mainly endemic to West African regions. According to genetic studies, it has undergone minimal evolutionary change, and its genome has remained chiefly stable during its evolutionary history. Clade IIa manifests with mild symptoms, including localised skin lesions, fever, and lymphadenopathy. It has played only a limited role in recent outbreaks, being constrained in its potential for human-to-human spread [14].

However, Clade II b has proven to be more dynamic and globally relevant as a subclade. It is the dominant strain driving the global Mpox outbreaks in 2022–2024. Clade IIb mutations are primarily seen in genes that influence viral replication and immune evasion, which are proposed to increase their transmissibility and adaptation to the human host. Epidemiological data from recent outbreaks have associated Clade IIb with atypical clinical presentations, including genital and perianal lesions, rarely seen in endemic cases. The geographic spread of Clade IIb to non-endemic regions, enabled by international travel and high-density human interactions, underlines its ability to disseminate rapidly. This subclade has attracted particular attention as a result of its implications for global public health [15].

Clade Ia, formerly designated as Clade I or Congo Basin lineage, is the most virulent branch of MPXV, uniformly linked with the highest case fatality rates (up to 10%) and persistent human-to-human transmission [6]. Comparative genomic research in recent years has shown that Clade I carries a more extensive and effective suite of immunomodulatory genes, contributing to immune evasion and increased pathogenicity. Particularly, genes like CrmB (cytokine response modifier B) and B15R (secreted IL-1β receptor homolog) are either intact or more transcriptionally active in Clade I than in Clade IIb to allow for host inflammatory response suppression [23]. Furthermore, C7L and K1L, the genes recognized to suppress host IFN-γ signaling and NF-κB activation, are well conserved in Clade Ia genomes [23, 24]. The genes play a role in helping the virus suppress major histocompatibility complex (MHC) expression and block apoptosis in infected cells, which leads to longer-term replication and systemic spread. This immune-evasive feature is responsible for the more virulent clinical presentation in Clade Ia infections, such as encephalitis and necrotic skin lesions. Clade Ia continues circulating mainly in the DRC, with a potential ongoing public health risk in endemic areas with poor surveillance. Its genomic stability and persistence of reservoirs need high-priority vaccination campaigns and genomic surveillance to avoid cross-border transmission [25].

The newly identified Clade Ib is an intermediate lineage characterised by specific genetic differences from the previously known subclades IIa and IIb. As epidemiological and clinical studies on the new subclade are yet to be investigated, the evidence from initial findings suggests that it has mixed features with those of subclades: middle-range transmissibility and virulence [26]. Such identification provides evidence of evolution in MPXV with the emergence of novel clades in the face of the selective forces of vaccination and antiviral use [16]. The subclades IIa, IIb, and Ib evidence that Clade II encompasses an evolutionary profile with which the virus could cope by making suitable responses in the face of change from its hosts or environment [27]. Identifying features characteristic of such subclades would thus help develop interventions. Furthermore, surveillance with genomics helps trace how the virus may have developed to emerge into highly virulent strains of lineages before these even became widespread [28].

Geographic distribution of clades

Ecological, demographic, and socioeconomic factors primarily drive the geographic distribution of MPXV clades. Each clade occupies a particular geographic niche characterised by the spread of its natural reservoirs, the extent of zoonotic transmission, and human activities facilitating the spread of infection [29]. Clade I MPXV predominantly circulates in countries such as the Democratic Republic of Congo (DRC), the Republic of Congo, Cameroon, and others in central Africa, where the dense tropical rainforest provides natural hosts for MPXV, mostly with rodents and monkeys. Human infections within these areas have been associated with hunting, consumption, and trade of bushmeat and direct contact with infected animals. Outbreaks of Clade I are typically regional, as this area is predominantly rural and population mobility is low. However, the absence of strong healthcare infrastructure in this region often leads to delayed detection of outbreaks and, consequently, higher mortality [12, 13]. Clade II, including subclades IIa and IIb, is present mainly in West Africa, particularly Nigeria, Ghana, and Sierra Leone. The semi-arid and savannah ecosystems of West Africa are suitable for the persistence of MPXV reservoirs, but they have lower ecological density than those in Central Africa. Clade IIa has remained confined mainly to remote endemic regions, with occasional outbreaks in rural areas. Human cases of Clade IIa are mainly linked to zoonotic transmission, and restricted human-to-human transmission ability has limited its geographical spread [30]. Clade IIb, however, has shown a capacity to expand beyond its ecological niches, becoming the causal agent of most of the current 2022–2024 global outbreak. The spread of this subclade was made possible through international travel, increasing urbanisation, and high-density activities, which led to cases in several parts of Europe, North America, Asia, and the Middle East. Unlike previous outbreaks restricted to rural endemic regions, Clade IIb infections have mainly been concentrated in urban settings, characterised by complex transmission dynamics involving protracted human-to-human contact. The geographic extent of Clade IIb highlights the virus's capacity for global spread and the necessity of international collaboration for its containment. Clade Ib, a newly identified variant clade, is limited in its geographical distribution, with the detection of only a few areas in West Africa. Its spread and impact require further genomic surveillance. Its geographic representation might be extended under favourable circumstances because it represents an evolutionary intermediate between Clade IIa and IIb. This geographic diversity of MPXV clades reveals complex factors that might be responsible for their distribution, including ecological conditions, reservoir species, human socioeconomic activities, and global connectivity. Therefore, this kind of geographic variability demands region-specific approaches to surveillance, prevention, and control, with the critical reminder of the importance of global health systems being watchful of the spread of non-endemic clades [31].

Epidemiology of Mpox

Historical epidemiological trends in endemic regions

Ecological factors, zoonotic transmission, and changes in human activity have all shaped the epidemiology of MPXV in endemic regions. Mpox was first identified in humans (a 9-year-old boy) in 1970 within the DRC through intensified smallpox surveillance programs. Over the following decades, it became recognised as a persistent zoonotic threat within Central and West Africa, with sporadic outbreaks often recorded in rural and forested regions [32]. In Central Africa, where Clade I predominates, cases of Mpox were historically associated with exposure to wildlife reservoirs, especially rodents and nonhuman primates. Hunting and the preparation of bushmeat were traditional practices that offered opportunities for zoonotic spillover. Outbreaks in this region have primarily been localised, with limited geographic spread, but the severity of the cases witnessed has been a marked demonstration of the virulence of Clade I. The epicentre of Mpox remains in Central Africa in the Congo Basin, where the interface between humans and wildlife continues to persist and drive the transmission cycle for the virus [13]. West Africa, the stronghold of Clade II, has had a different epidemiological pattern. Cases in this region have been less severe, with lower CFRs than in Central Africa. The semi-arid environments in West Africa support different reservoir species, influencing zoonotic transmission dynamics. Countries such as Nigeria, Sierra Leone, and Ghana have reported periodic outbreaks, often linked to human incursions into wildlife habitats. It was significant that the Nigerian outbreak between 2017 and 2019 was one of the largest in the region, with over 300 suspected cases, indicating increasing public health significance in Clade II [13, 33]. Historically, another determinant underpinning the rise of Mpox in endemic areas is the interruption of vaccination for smallpox campaigns after it was globally declared eradicated in the early 1980s. Smallpox vaccination led to cross-protection between the viruses because of the antigenic similarity. The end of vaccination efforts left an immunity gap, thereby increasing susceptibility among younger, unvaccinated populations. This immunity gap was seen during the 1996–1997 outbreak in the DRC, where cases were reported at a much higher rate, calling attention to Mpox as an emerging infectious disease [34]. Other than immunity gaps, ecological and climatic conditions, such as deforestation and urbanisation processes and changes to wildlife habitats, have influenced the shifting epidemiology of Mpox. Increased human-wildlife reservoir interface exposure poses an increased spillover threat for zoonotic spillover. Other areas where mpox outbreaks require extensive efforts involve the endemic setting due to inadequate healthcare services, delayed notification, and expense to control in a resource-strained setting [35, 36]. Enhanced surveillance, education, and health access are critical for mitigating the ongoing impact of Mpox while developing risk-minimizing prospects of larger-scale outbreaks.

Recent outbreaks and case statistics (2022–2024)

The epidemiology of Mpox was radically changed in 2022 when the virus jumped its traditional borders of endemicity and triggered a series of outbreaks outside endemic regions. These led to the first episode of sustained transmission across the world, bringing Mpox into global public health discourse. The World Health Organization declared Mpox a public health emergency of international concern by mid-2022, reflecting its rapid geographic expansion and the emergence of new epidemiological patterns [37]. The 2022–2024 outbreaks were mainly driven by Clade IIb, a subclade showing increased transmissibility and adaptability to human hosts. As of late 2024, epidemiological surveillance has documented over 85,000 confirmed cases in more than 100 countries; most of these are reported in Europe, North America, and South America. Notably, whereas previous historical outbreaks in endemic regions were frequently associated with zoonotic spillover, this outbreak is characterised by transmission between humans. Intimate or sustained body contact, particularly in high-density social networks, emerged as the mode of transmissible spread, concentrated particularly among men who have sex with men (MSM) [38]. A closer look at the outbreak trend showed several significant trends. Firstly, cases of Mpox during this time were concentrated in urban settings where high population density allowed for the virus's rapid spread. This was unlike previous outbreaks in rural endemic regions. Secondly, unusual symptoms of cases often included genital and perianal lesions, which were less commonly seen in previous outbreaks. This varied the presentation, posing diagnostic challenges, especially in healthcare facilities unfamiliar with Mpox [39, 40]. Geographic variability in case numbers was also observed; countries like Spain, the USA, and Brazil accounted for the most significant number and thus significantly contributed to the global burden. Relatively few cases were reported by nations lacking international travel or with strong public health infrastructures. Mpox spread globally at such velocities and quickly due to global connectivity, making international coordination critical to response efforts [41]. Despite the size of the outbreaks, global CFR was low, typically below 1%, a marked reduction from what was observed in the endemic regions, mainly for Clade I infections. There are several reasons why the CFR was lower than expected. Early detection of cases combined with supportive care and pre-existing vaccination in older populations brought partial immunity. Nonetheless, the morbidity burden remained relatively high, with patients having a prolonged illness and facing social stigma [42]. The 2022–2024 outbreaks have underscored the importance of enhanced global surveillance, public health preparedness, and targeted interventions. Control measures, including mass vaccination campaigns using modified vaccinia Ankara (MVA)-based vaccines, which are protective against MPXV, and public awareness campaigns with community engagement are essential in reducing transmission, especially among high-risk groups. Recent outbreaks have repositioned Mpox as a threat to global health, demanding investment in research, surveillance, and healthcare infrastructure over the long term. The lessons learned during this period are how early detection and rapid response could mitigate future outbreaks through equitable access to diagnostic tools and vaccines.

Case fatality rates across different clades

CFRs are among the most essential epidemiological indicators of monkeypox's severity and public health implications. The significant difference in CFRs between Clade I and II can be ascribed to the pathogen's genetic, clinical, and extra-genetic diversity and the effect of healthcare delivery, population immunity, and management strategies undertaken during the outbreaks. The Central African clade, or Clade I, has the highest historical CFR of up to 10%. Clade I Mpox is also associated with severe systemic manifestations, including widespread skin lesions, fever, and complications such as dehydration, secondary bacterial infections, and encephalitis. The high CFR reflects both the virulence of Clade I and the limited healthcare infrastructure in endemic regions such as the Democratic Republic of Congo (DRC) [43]. Historical epidemics in the Congo Basin have also affected particularly vulnerable individuals: children, pregnant women, and immunosuppressed subjects for whom there was little available supportive care. Its ability to perpetuate transmission between humans renders management of this clade an added challenge, underscoring the need for a focused approach in interventions in regions of outbreaks [44]. In sharp contrast, Clade II, including subclades IIa and IIb, have CFRs dramatically lower, at less than 4% in most reported instances [38]. Infections with Clade IIa are generally zoonotic and result in mild clinical expression, such as localised skin lesions and fever that is often self-limiting and resolves with minimal complications. This subclade seems restricted chiefly to the endemic regions of West Africa, and there is little human-to-human transmission associated with this subclade [45]. Clade IIb has emerged as the predominant clade in the recent global outbreaks. While reporting lower CFRs (typically below 1%), Clade IIb has features of higher transmissibility with atypical clinical presentations. The global spread of this clade during the 2022–2024 outbreaks against this backdrop, coupled with the diagnostic difficulties in non-endemic regions, puts a seal on the dynamics of this subclade [46]. The newly designated Clade Ib appears to be at an evolutionary midpoint between Clade IIa and IIb, with CFRs closer to those of Clade IIa. Despite the work done to lessen its clinical impact, pre-existing data suggests that Clade Ib has moderate virulence and transmissibility. Its emergence underscores the dynamic evolution of MPXV and the importance of continuous genomic surveillance in tracking new lineages and their potential public health relevance [47]. Although genetic underpinnings exist to the variation among CFRs across the clades, other factors, including the quality of healthcare services, early detection, and population immunity, also determine the impact. Particularly in endemic areas, limited access to medical care and late response to outbreaks contribute to enhanced mortality, especially from infections with Clade I. In non-endemic countries, recent outbreaks have seen reduced severity and mortality due to the adequate availability of supportive care with Clade IIb. Vaccination campaigns, primarily based on the smallpox vaccine, have also contributed to a decline in death rates from MPXV by offering partial protection through cross-reactivity. The disparity in CFRs between clades should be addressed with clade-specific strategies for managing Mpox outbreaks. For Clade I, enhancing healthcare infrastructure in endemic areas and increasing access to antiviral therapies is crucial. For Clade IIb, rapid detection tools and specific vaccination campaigns among targeted groups should be ensured to avoid high-scale outbreaks. This has to be followed by ongoing research into clade-specific virulence mechanisms and the development of more effective interventions to help control the Mpox outbreak at the global level [48].

Transmission dynamics

Mechanisms of transmission (zoonotic vs. human-to-human)

MPXV is mainly spread through two pathways: zoonotic spillover and human-to-human spread. Both of these pathways determine the epidemiology of the disease and are relevant: zoonotic transmission drives infections in endemic regions, while human-to-human transmission has driven the most recent outbreaks in the non-endemic global environment. Zoonotic transmission occurs when humans come into direct or indirect contact with infected animals. The natural reservoirs of MPXV include many small mammals, particularly rodents such as African squirrels, Gambian pouched rats, dormice, and non-human primates [18]. Human exposure occurs usually due to hunting, bushmeat preparation, or handling infected animals, providing opportunities for the virus to cross the species barrier. Other indirect transmission routes include contact with contaminated materials, such as bedding or clothing contaminated with bodily fluids or lesions of an infected animal. Viral biomarkers of persistent transmission are intact immunomodulatory genes like CrmB and K1L, which dampen host immune activity, whereas viral DNA polymerase gene mutations and ankyrin-repeat proteins have been implicated in increased replication and adaptation to the human host, which enables both zoonotic spillovers and effective human-to-human transmission [23, 49]. The ecology of zoonotic transmission highlights human-wildlife interactions as one of the factors maintaining the endemicity of Mpox in Central and West Africa [50]. Although less efficient than zoonotic transmission, human-to-human transmission has become more prominent in recent outbreaks, particularly those caused by Clade IIb. Interhuman transmission occurs through direct contact with infectious lesions, bodily fluids, or respiratory secretions of an infected individual. Prolonged close physical contact, including sexual contact, has been identified as a key driver of human-to-human spread [51]. Intimate contact emerges as a core feature facilitating the spread of the 2022–2024 global outbreaks, highlighting the critical role that it plays and how many reported cases were due to networks of MSM. Significantly, transmission by fomites- such as soiled linen or contaminated surfaces facilitates spread, although its relative role remains under investigation [52]. Although possible, respiratory transmission is thought to be limited compared to other Orthopoxviruses such as the variola virus. It is transmitted via respiratory droplets during close contact, but long-distance aerosolised transmission under natural conditions appears unlikely. This characteristic helps explain why most Mpox outbreaks are local and why physical contact is the primary mode of human-to-human transmission [53]. Environmental, social, and demographic factors further mediate this interaction. For instance, while human encroachment into the habitats of the wildlife hosts fuels zoonotic spillovers in endemic regions due to deforestation and hunting, coupled with demographic changes, non-endemic regions witness increased contributions of human-to-human transmission using urbanisation, international travel, and behavioural patterns. These factors may explain the shifting dynamics of the transmission observed over recent outbreaks: Clade IIb infections spreading predominantly within human populations, showing an increased transmissibility compared with its predecessors. The dual modes of transmission highlight the difficulty of controlling Mpox. Depending on local conditions, Strategies must focus on zoonotic sources and human-to-human transmission routes. Effective measures in endemic regions include reduction of human-animal contact, community education, and strengthening surveillance in wildlife reservoirs. In non-endemic areas, public health efforts should concentrate on the rapid identification of cases, isolation protocols, and vaccination of high-risk populations to break chains of transmission Fig. 2.

Fig. 2.

Transmission pathways of monkeypox virus

Factors influencing transmission rates

MPXV is transmitted according to a complex interplay between biological, environmental, and socio-behavioural factors, which determines its rate of spread. Understanding these factors is critical to designing effective interventions that mitigate its spread. Genetic variation among MPXV clades is the most significant biological factor influencing transmission rates. Clade I has higher transmissibility than Clade II, partly because of its increased ability to maintain human-to-human transmission. Clade IIb, however, has shown remarkable adaptability in recent global outbreaks, with mutations that may increase its transmissibility within human populations. These genetic differences highlight the need for clade-specific research to understand how viral evolution shapes transmission dynamics [54]. Host immunity is also crucial in determining the rates of transmission. The smallpox eradication campaign of the 1980 s deprived much of the world's population of immunity against MPXV because the smallpox vaccine provided cross-protection against MPXV. In endemic countries, waning immunity in older adults and a lack of vaccination in younger individuals has created an immunity gap that makes populations susceptible to zoonotic and human-to-human transmission. Similarly, immune-compromised individuals, such as incompletely treated HIV patients, are also at risk of acquiring and spreading the virus [55]. Environmental factors, especially in endemic areas, also determine the transmission rate. Human activities such as deforestation and agricultural expansion into wildlife habitats increase the occurrence of zoonotic spillover events. Seasonal fluctuations, which affect the activity of MPXV reservoir species, also contribute to the likelihood of human exposure. In non-endemic areas, urban environments with high population density enhance the potential for human-to-human transmission, as observed during the 2022–2024 outbreaks [56]. Socio-behavioural determinants such as social networks and mobility are crucial transmission dynamics, including factors behind 2022–2024 global outbreaks, primarily pointing out the aspect that most intimate as well as continuous close physical interactions occurring in limited demographical characteristics of population among them, MSW; massive dense aggregation increased spatial spread mainly during Clade IIb thus revealing influence that human behaviour assumes under modern culture towards the movement of the viruses. Stigma and misinformation during outbreaks can also impede public health efforts, leading to underreporting cases and delayed intervention. Healthcare access and public health infrastructure significantly impact transmission rates, especially in resource-limited settings. In endemic areas, delayed case detection, poor isolation measures, and lack of medical resources enhance the spread of MPXV. However, countries with strong healthcare systems and vaccination strategies have been able to control transmission effectively during recent outbreaks [57, 58]. Targeted approaches aimed at different drivers of transmission operating in endemic and non-endemic areas are desirable to control outbreaks effectively. For the endemic area, it is vital to strengthen surveillance systems, educate local communities, and reduce human-wildlife interaction. In the non-endemic regions, early detection, vaccination of high-risk groups, and communication aimed at behaviour change to reduce exposure risks are necessary. Understanding and addressing these determinants are essential to reduce the global burden of Mpox.

Comparative analysis of transmission dynamics between clades

MPXV transmission dynamics vary greatly among its clades, corresponding to differences in genetic makeup, host interactions, and environmental conditions. Clades I and II have different epidemiological profiles due to their differing zoonotic and human-to-human transmission patterns and, therefore, different public health impacts. Clade I, endemic to Central Africa, has a higher capacity for human-to-human transmission. This clade's transmissibility is due to better replication efficiency and the virus's immune-evasion ability. During close interactions, human-to-human transmission in Clade I is often maintained through direct contact with lesions, bodily fluids, or respiratory droplets. While zoonotic spillovers are a primary transmission mode for outbreaks in Clade I, the potential for secondary transmission makes the clade responsible for the relatively more extensive and protracted outbreaks in less resource-rich settings. Furthermore, infections by Clade I are often associated with severe systemic manifestations that might enhance the probability of viral shedding and thereby ease transmission [59]. On the contrary, Clade II, encompassing subclades IIa and IIb, has always been known for minimal human-to-human transmission. Clade IIa, primarily found in West Africa, mainly depends on zoonotic transmission from wildlife reservoirs, although human-to-human transmission is less frequent and mainly among household contacts. However, during the global outbreaks of 2022–2024, Clade IIb emerged and presented a different transmission pattern. The enhanced ability for human-to-human transmission was observed in Clade IIb, facilitated by mutations that enhance viral adaptation to human hosts. These outbreaks highlighted the importance of close physical contact, particularly within intimate networks, as the primary mode of spread. In contrast to Clade I, Clade IIb transmission has been more shaped by modern social behaviours, including high-density gatherings and international travel, contributing to its rapid global spread [60, 61]. Another difference between the clades is the environmental and ecological determinants of transmission. Clade I is associated with dense forest ecosystems in the Congo Basin, where humans frequently contact wildlife through hunting and bushmeat preparation. These practices frequently provide zoonotic spillovers that sustain the virus's endemicity in the region. The difference lies in the semi-arid and savannah ecosystems in West Africa, where reservoir species and human activities vary. It has been pointed out that Clade IIb expanded into the urban environment in non-endemic areas, where the role of human-mediated factors has been underscored [23]. The clinical presentations associated with each clade also influence transmission dynamics. Clade I’s severe symptoms, such as widespread skin lesions and systemic illness, may increase the likelihood of viral shedding, particularly in close-contact settings. Conversely, Clade II infections, particularly those caused by Clade IIb, have been associated with atypical presentations, such as genital and perianal lesions, which may prolong viral shedding and facilitate undetected transmission. These differences highlight the necessity of clade-specific diagnostic and surveillance approaches [62]. Clade I’s transmission dynamics are heavily influenced by its virulence and proximity to wildlife reservoirs. In contrast, Clade IIb’s recent success in global spread reflects its adaptability to human-to-human transmission and modern social behaviours. Understanding these differences is critical for tailoring public health strategies. In Central Africa, efforts should be made to reduce zoonotic spillovers and improve healthcare access. For Clade IIb, transmission control would require vigorous contact tracing, vaccination campaigns, and community engagement to address human-mediated spread effectively.

Virulence and pathogenicity

Differences in virulence among clades

The virulence of MPXV differs considerably between its clades, which is influenced by genetic differences and their impact on host–pathogen interactions. Clade I, which is mainly found in Central Africa, hosts significantly higher virulence than Clade II, which is a common occurrence in West Africa and non-endemic regions. However, due to such variabilities, disease severity and clinical outcomes have become critically important in designing appropriate public health strategies for outbreak management. Clade I infections are characterised by high-grade fever, extensive lymphadenopathy, and widespread skin lesions. These often progress to secondary complications such as bacterial superinfections, sepsis, and encephalitis, leading to CFRs of 5–10%. This high virulence is due to genetic features of Clade I that enhance viral replication, immune evasion, and tissue tropism. Such mutations in Clade I have been identified to precisely modulate the interaction of this virus with host immune responses to suppress antiviral defences and establish a more invasive infection. The severity of Clade I infections has become a significant public health challenge in Central Africa, significantly where limited healthcare infrastructure exacerbates its impact [63, 64]. In contrast, Clade II has shown significantly reduced virulence, with CFRs generally less than 3%. Subclade IIa, primarily circulating in West Africa, is characterised by mild to moderate disease severity, typically restricted to localised skin lesions and self-limiting febrile illness. Clade IIb, which emerged as the predominant strain during the 2022–2024 global outbreaks, has shown an intermediate level of virulence. Although it shares the bulk of the clinical milder profile of Clade II, Clade IIb is associated with atypical manifestations, such as genital and perianal lesions. This localised symptomatology may prolong viral shedding and obscure diagnosis but less frequently causes severe systemic disease. Genetic studies indicate that Clade IIb possesses mutations that favour its transmissibility, but those mutations do not make Clade IIb much more virulent than Clade I [65]. Recently discovered Clade Ib falls between the two evolutionary intermediates, Clade IIa and IIb. Preliminary data suggest that the virulence is closer to Clade IIa, where most clinical outcomes have been mild. More studies on the genome and epidemiology are necessary to correctly understand its pathogenic potential [16]. Differences in virulence among the MPXV clades are also crucial for public health responses. Clade I’s high virulence necessitates aggressive outbreak containment measures, including early diagnosis, isolation, and access to supportive care. Conversely, the milder nature of Clade II infections allows for a broader focus on preventing transmission, mainly through vaccination and public awareness campaigns. Further research into the genetic determinants of virulence is essential to understand the mechanisms underlying these differences and to develop targeted antiviral therapies.

Impact of clade variations on clinical outcomes

Recently discovered, Clade Ib is an evolutionary intermediate between Clade IIa and IIb. Preliminary data indicate that its virulence is closer to Clade IIa's, with mild clinical outcomes in most cases. However, more genomic and epidemiological studies are required to assess its pathogenic potential fully [16]. The differences in virulence among MPXV clades have significant implications for public health responses. Clade I’s high virulence necessitates aggressive outbreak containment measures, including early diagnosis, isolation, and access to supportive care. On the other hand, Clade II infections being less virulent enables broader concerns on transmission prevention, namely prevention by vaccination and public awareness campaigns. Further research into the genetic determinants of virulence is necessary to understand the mechanisms underlying these differences and to develop targeted antiviral therapies. In contrast, Clade II infections cause, in general, milder clinical outcomes due to the lower virulence of this clade. Subclade IIa is mainly restricted to endemic areas of West Africa and typically shows localised skin lesions, mild febrile symptoms, and a self-limiting course of the disease in most patients. Severe outcomes are exceptional and usually occur in immunocompromised or those suffering from predisposing comorbid conditions. The clinical profiles of Clade IIb, which became the predominant strain during the 2022–2024 global outbreaks, are similar but with some differences. Most infections caused by Clade IIb presented atypically, with lesions mainly in the genital and perianal regions. These atypical presentations made clinical recognition and diagnosis challenging, especially in non-endemic regions where healthcare providers were less familiar with Mpox [66]. Although the CFR for Clade IIb is still very low, at less than 3.6% globally, some patients had prolonged illness and complications, significantly when diagnosis or treatment was delayed. The milder clinical course of Clade II infections often permits outpatient management, thus reducing the burden on healthcare systems. However, the atypical nature of some Clade IIb cases requires greater vigilance in clinical settings to ensure timely diagnosis and intervention [67]. The newly identified Clade Ib remains under exploration. Still, from preliminary observations of its clinical outcomes, it seems more inclined to the trend of Clade IIa, which has primarily minor symptoms and low mortality levels. Further study is required to determine if Clade Ib has some characteristic clinical features and outcomes that distinguish it from other Clade II subclades [68]. Understanding the clade variations is essential to predicate medical management and a public health response. Where Clade I prevails, well-equipped healthcare infrastructure and easy access to antiviral treatment will reduce morbidity and mortality. In the case of Clade II infections, especially Clade IIb, there is a need for improving diagnostic sensitivity with prompt management of atypical cases. Comparative studies on the clinical behaviour of MPXV clades will provide crucial information on the virus's pathogenic mechanisms and inform outbreak control and treatment optimisation strategies.

Animal models for studying virulence differences

Animal models have contributed significantly to the advancement of understanding MPXV virulence and its heterogeneity between clades. Such models are extremely important for determining mechanisms behind disease severity, host–pathogen interaction, and efficacy of therapeutic interventions. Due to the contrasts in virulence between Clade I and II, animal studies are now critical to determine the genetic and phenotypic factors contributing to these differences. Rodents, including prairie dogs and mice, are some of the most used animal models to study MPXV. It was shown that, notably, prairie dogs had proved crucial in faithfully replicating the natural disease course of Mpox. MPXV-infected prairie dogs typically manifested clinical manifestations that included rash, lethargy, and weight loss, mimicking a similar profile observed in humans. The model was particularly informative regarding infections that lead to the establishment of a much more aggressive disease phenotype by yielding higher viral loads and systemic dissemination. Researchers have identified several key genetic markers through prairie dog studies, such as genes involved in immune modulation and viral replication, which are associated with enhanced virulence [69, 70]. The second critical model of MPXV virulence was non-human primates, specifically rhesus macaques and cynomolgus monkeys. The models used here are so like human disease that they were indispensable for studies on Clade I and Clade II infections. The results of studies on NHPs indicated that Clade I produced more significant tissue damage, more pronounced viremia, and more extended periods of viral shedding compared with Clade II. Additionally, these models have been used to evaluate the efficacy of smallpox vaccines and antiviral treatments, providing insight into how therapeutic responses vary between clades [52, 71, 72]. Mouse models, especially those involving genetically modified mice, have also significantly contributed to understanding clade-specific differences in Mpox. Immunocompromised mouse strains, such as those lacking type I interferon receptors, have been used to study the virus's ability to evade host defences. These studies have demonstrated that Clade I exhibits more excellent immune evasion capabilities, likely contributing to its higher case fatality rates. While mice are less responsive to natural MPXV infections than other models, their utility in genetic studies has been invaluable for understanding host–pathogen interaction [73, 74]. There is a limitation on animal models; they are only helpful. Diseases and immune responses can vary due to the biology of host species, which will not appropriately represent infection in humans. For example, although the prairie dog effectively replicates some aspects of Mpox, their responses to Clade II infections may downplay the ability of the virus to be transmissible from one human to another. Furthermore, studies done on NHPs are cost-effective and raise moral issues, requiring careful study designs and prioritised experiments [75], Table 2.

Table 2.

Overview of diagnostic methods for the detection of monkeypox virus

Method	Description	Strengths	Limitations	References
Polymerase chain reaction (PCR)	Molecular detection of MPXV DNA, targeting specific genes	High sensitivity and specificity; gold standard	Requires advanced labs and trained personnel	[76]
Next-generation sequencing (NGS)	Comprehensive genomic sequencing of MPXV for clade identification	Detects mutations; tracks viral evolution	High cost; complex analysis; time-intensive	[77, 78]
serology (ELISA)	Detects antibodies against MPXV in patient samples	Useful for epidemiological studies	Cross-reactivity with other Orthopoxviruses; limited for acute diagnosis	[79]
Rapid diagnostic tests (RDTs)	Lateral flow assays for antigen or antibody detection	Portable; quick results	Lower sensitivity compared to PCR	[80, 81]
Loop-Mediated Isothermal Amplification (LAMP)	Isothermal amplification of MPXV DNA	Portable; fast; field deployable	Lower sensitivity and specificity than PCR	[80, 81]
Clinical diagnosis	Based on characteristic symptoms, such as fever, rash, and lymphadenopathy	Useful in resource-limited settings	Overlaps with other illnesses; relies on clinician expertise	[82]
Viral culture	Isolation of live virus in cell culture	Confirms live virus presence	Requires BSL-3 labs; time-consuming	[82]
CRISPR-based assays	Uses CRISPR-Cas systems for precise nucleic acid detection	Highly specific, portable	Emerging technology; limited availability	[83, 84]
Recombinase polymerase amplification (RPA)	Isothermal DNA amplification at ~ 37–42 °C; results in ~ 15–20 min	Ultra-rapid; portable; suitable for low-resource settings	Still under optimization; risk of cross-contamination	[85]

Diagnostic tools for the detection of Mpox

Overview of current diagnostic methods (PCR, serology, etc.)

A positive diagnosis of MPXV ensures effective outbreak management and treatment; diagnostic tools ensure the confirmation of the cases, distinguishing them from other feverish illnesses and guiding appropriate public health action. The most frequently used methods currently for Mpox detection are molecular techniques and serological assays, with considerable clinical evaluation as the approach for diagnosis. Polymerase Chain Reaction (PCR) is the best diagnosis mode, as it's considered the gold standard for Mpox diagnosis due to its high sensitivity and specificity. PCR tests focus on specific genetic sequences of MPXV, like the HA gene or DNA polymerase gene, to ensure precise virus identification. Such tests can distinguish MPXV from other Orthopoxviruses, such as vaccinia and variola. Real-time PCR (qPCR) increases the sensitivity of the diagnosis by quantifying viral DNA and gives an idea of the viral load and disease progression. PCR testing requires sophisticated infrastructure in the lab, a trained workforce, and supplies of reagents, which present a challenge in such resource-limited settings [76]. Serological tests also include ELISAs that detect the antibodies raised in response to an infection with MPXV. These tests provide a retrospective confirmation of exposure. While not effective as a diagnostic tool for early diagnosis, as it takes some time to produce antibodies, serology is helpful in epidemiological research and in discerning previous infections within communities. Cross-reaction with antibodies to other Orthopoxviruses like vaccinia can make serological tests less specific, so results need careful interpretation [79]. Even with laboratory-based tests, clinical diagnosis is essential in detecting Mpox. Characteristic symptoms, including fever, lymphadenopathy, and vesicular-pustular rash, often establish initial clinical suspicion. Mpox can be atypical, though, particularly with the most recent Clade IIb outbreaks, where lesions are concentrated within the genital and perianal areas. Such presentations are pretty atypical, hence the necessity of laboratory confirmation to avoid misdiagnosis in regions where Mpox is less likely to be known to health providers. Viral culture techniques are other diagnostic methods that can be utilised to detect MPXV. Although the live viruses can be isolated through cultures, the methodology is time and labour-intensive. It also calls for BSL-3 facilities, which restrain its widespread adoption [82]. Another more promising avenue on the horizon, especially in developing regions, has been the discovery of point-of-care diagnostics for improvement in the Mpox detection methodology. Lateral flow assays based on RDT or isothermal techniques like LAMP have demonstrated strong potential for site diagnostic testing. It gives better output than traditional PCR and is quicker. Still, its lesser sensitivity toward the test when compared with traditional PCR demands confirming tests to render an accurate result for confirmation [80, 81]. The choice of diagnostic method depends on several factors, including the availability of laboratory resources, the stage of infection, and the patient's clinical presentation. Although PCR is still the cornerstone of Mpox detection, advances in diagnostic technologies are being pursued to overcome existing limitations and increase access to accurate testing worldwide. Future research in animal models should further refine existing systems and develop new models that better resemble human Mpox infections. Techniques for genetic engineering of more representative mouse models can be explored in addition to advances in organoid and in vitro systems to study clade-specific differences in viral behaviour. These will further enlighten MPXV pathogenesis and advance targeted therapies and vaccines, explicitly addressing the challenges in different clades.

Advances in diagnostic technologies

In the last decade, advances in diagnostic technologies have significantly improved the sensitivity, specificity and speed of detection and management of MPXV infections. These advancements overcome the weaknesses of traditional methods and provide better detection, diagnosis, and management options. Global Mpox outbreaks, especially those caused by Clade IIb, have allowed the development and implementation of advanced diagnostic technologies to support an effective public health response. Next-generation sequencing (NGS) is also a state-of-the-art MPXV-detection method that allows for deep characterisation of complete viral genomes to identify clades and subclades precisely. It dramatically helps shed light on genetic diversity, mutational patterns, and all aspects of the evolution of viruses of interest, allowing for tracking dynamic outbreak characteristics. Unlike PCR, which targets specific genes, NGS captures the whole genome, making it a powerful tool to identify novel lineages such as Clade Ib. NGS is, in fact, expensive and complex and has been mainly restricted to research laboratories up until now. Advances in portable sequencing platforms, such as that available from Oxford Nanopore Technologies in MinION, are opening up the full range of its application in field settings [77, 78]. Point-of-care diagnostics has proved revolutionary in making more detection accessible, especially for cases in resource-scarce, remote, or inaccessible locations. Technologies, including loop-mediated isothermal amplification (LAMP) and recombinase polymerase amplification (RPA), allow quicker and more portable ways to complement what has conventionally been carried out using PCR, with results as fast as 30 min, useful specifically for outbreaks [86]. However, lateral flow immunoassay (LFIA) detects antigens and/or host antibodies and gains recognition as straightforward yet economical point-of-care (POC) diagnostics. As an initial screening tool, despite its limited sensitivity relative to PCR, its speed of test availability makes such screening tools particularly appealing [87]. CRISPR-based diagnostics exploit the specificity of these enzymes to selectively detect MPXV nucleic acids. New technologies, for example, Cas12 and Cas13, exploit the specificity of CRISPR-Cas systems toward the detection of infectious diseases such as MPXV. Various portable formats of CRISPR diagnostics that can be performed rapidly and precisely in different contexts include SHERLOCK (Specific High-sensitivity Enzymatic Reporter UnLOCKing) and DETECTR (DNA Endonuclease Targeted CRISPR Trans Reporter). These tools are promising for filling the gap for decentralized Mpox testing in massive outbreaks [83, 84]. The integration of AI and ML into diagnostic systems is changing the face of detecting Mpox. Clinicians can run these AI algorithms on clinical data, imaging results, and genomic sequences to enhance diagnostic accuracy and predict the disease severity. AI-based platforms are under consideration for automating the analysis of complex datasets generated by advanced diagnostic tools such as NGS and CRISPR assays that consume much time from laboratory personnel and increases the turnaround times [86]. Along with technological advancements, there is also increasing interest in multiplex diagnostic assays that can simultaneously detect MPXV and other pathogens that might present with similar symptoms, like varicella-zoster virus (VZV) or herpes simplex virus (HSV). These multiplex platforms are highly useful in areas where co-circulation of several pathogens complicates differential diagnosis [88]. These benefits notwithstanding, the challenges that need to be addressed in order to scale up the deployment are: cost, regulatory hurdles, and the requirement for specialised training that limits the accessibility of these diagnostics in low-resource settings. This can only be done through international cooperation, funding support, and capacity-building efforts to promote equal access to these cutting-edge Mpox detection technologies. Innovation in diagnostic tools continues to revolutionise the detection of Mpox. These technologies will evolve and may potentially improve the management of outbreaks, enable early detection, guide targeted interventions, and reduce the global burden of Mpox.

Challenges in detection across different clades

There are many challenges in detecting MPXV infections across clades due to differences in their genetic makeup, clinical presentations, and epidemiological contexts. This has further been complicated by disparities in the diagnostic capacity in different regions, especially in the endemic areas with limited resources. Overcoming such obstacles is paramount to enhancing the accuracy and access of Mpox diagnostics globally (Fig. 3). The genetic diversity between MPXV clades, especially between Clades I and II, is a significant challenge. Although PCR is the gold standard for MPXV detection, the genetic variability across clades requires well-designed primers and probes to ensure high sensitivity and specificity. Specific PCR tests, initially based on Central Africa Clade I, underperformed in testing the second major clade. These underperformed or failed tests highlight the ongoing task of maintaining updated diagnostics as more evolutionary lineages come into view with increasing numbers, which also needs to ensure sensitivity to these types [89]. The clinical presentation of Mpox varies significantly between clades, with additional diagnostic difficulties. Infections caused by Clade I tend to be very severe, associated with widespread cutaneous lesions and systemic involvement that includes high fever, making it straightforward to develop a clinical suspicion in endemic settings. In the case of Clade II, especially Clade IIb, the symptoms appear atypical, with genital and perianal lesions. These localised manifestations may mimic other STIs, including herpes simplex virus or syphilis, potentially causing delayed treatment due to misdiagnosis. In addition, more subtle presentations of Clade II infections in non-endemic areas rely heavily on clinicians' heightened awareness and confirmatory laboratory diagnosis [90, 91]. The main difficulty with the detection of MPXV is enhanced by the fact that in the endemic areas, there is limited access to diagnostic tools such as PCR or next-generation sequencing (NGS), mainly due to their cost, although both have their relevance. Here, Clade I and Clade IIa prevail. Still, basic serological tests or clinical diagnosis are mainly employed and have less sensitivity and specificity for detecting this infection, possibly increasing underdiagnosis or misdiagnosis. Besides, weak infrastructure, inadequately prepared personnel, and logistical difficulties that affect sample transport delay the cases' early detection, further causing delays in the public health responses [86]. Cross-reactivity with other Orthopoxviruses is another challenge in the diagnosis. Serological tests, including ELISAs, frequently detect antibodies that cross-react with multiple Orthopoxviruses, including smallpox and vaccinia. This makes them less helpful in differentiating between MPXV clades or confirming recent infections. Although promising for point-of-care diagnostics, rapid antigen tests are likely to have difficulty distinguishing between closely related Orthopoxvirus species [92].

Fig. 3.

Known clade distribution of MPXV as of 13 April 2025. Clade detection includes cases associated with local transmission and imported cases. Data is based on sequencing databanks, published literature, epidemiological links, and communication to WHO since 2022. (Source of figure—https://worldhealthorg.shinyapps.io/mpx_global/)

In non-endemic settings, the unfamiliarity of Mpox with the healthcare workforce complicates the diagnostic process because it has recently driven outbreaks in the Clade IIb setting (Fig. 3). Limited clinical experience with Mpox may result in initial misdiagnosis when the cases occur atypically. The unavailability of accessible point-of-care tests further delays confirmation, hence calling for building global capacity and training programs to better prepare for diagnostic capabilities. A multifaceted approach is required to overcome these challenges. Investments in genomic surveillance are needed to continuously monitor the spread of new clades and lead the way in developing clade-specific diagnostic tools. Increasing access to advanced diagnostic systems, including field-portable PCR systems and assays based on the CRISPR phenomenon, should raise the detection probability in endemic and non-endemic areas. At the same time, education-based clinical awareness supported by training initiatives and inclusion within broader infectious disease platforms could eventually improve early recognition and outbreak containment [93]. As Mpox evolves, detection in various clades will be necessary for effective surveillance, timely intervention, and patient outcomes. Diagnostic advancements will only be possible through the concerted efforts of governments, research institutions, and global health organisations to ensure that benefits are equitably distributed and responsive to the epidemiological diversity they are supposed to meet.

Public health implications

Strategies for outbreak management and prevention

It would need a more multi-tiered and comprehensive approach: robust surveillance, public education, vaccination, and international cooperation to manage Mpox outbreaks and prevent spread efficiently. The virus is zoonotically originating, genetically diverse, and newly widely spread throughout the world; its epidemiological contexts and clade-specific characteristics may require adjusted strategies. Stronger surveillance systems form the core of Mpox outbreak management. Early case detection depends on integrated surveillance mechanisms integrating clinical, laboratory, and genomic data to detect infections early. Laboratory networks should be strengthened, especially in endemic areas, to enhance diagnostic capacity and allow for the rapid confirmation of cases. Sentinel surveillance involves monitoring specific high-risk populations or geographic areas and can provide early warnings of potential outbreaks. It is also critical to track clade emergence for new clades, like Clade Ib, and their mutations potentially affecting transmissibility or virulence [94, 95]. Contact tracing and isolation are integral elements of outbreak containment. Identification and follow-up of contacts to confirmed cases could substantially reduce the occurrence of secondary transmission. Such a strategy was successful in both endemic settings and during the global outbreaks caused by Clade IIb in the recent past. Isolation strategies should be formulated according to the resources available to effectively contain the transmission while ensuring the appropriate care for patients [96]. Vaccination campaigns are an essential part of the prevention of Mpox transmission. MVA-based vaccines, developed originally for smallpox, have proven effective against MPXV and are the primary means to control outbreaks. Targeted vaccination strategies, including ring vaccination, involve immunising close contacts of confirmed cases to provide a protective barrier against the virus. The other populations are also to be prioritised, such as health workers, laboratory staff, and people with previous exposures in the Mpox-affected communities: vaccination production and equitable distribution to prevent unequal accessibility between endemic and non-endemic regions [19, 20]. Communities engaged and educated are critical ingredients in the achievement of awareness and in reducing the stigma associated with Mpox. Communication strategies must effectively share information on avenues of transmission and symptoms and preventative measures. About Clade IIb, most of which outbreaks occurred through intense and prolonged direct contact, their public health communication should be tactically sensitive to and responsive to local needs while seeking to correct certain misconceptions among the affected groups. Engagement with local leaders and organisations helps establish trust and ensure compliance with the preventive measures [97]. Especially important in endemic areas, where wild contacts contribute to its persistence, the prevention of zoonotic transmission requires public education among communities on handling bushmeat and contact with the wildlife reservoirs. Safe preparation methods for food should be encouraged to reduce the opportunities for zoonotic spillover alongside alternative protein sources. Conservation in terms of maintaining habitats and surveillance of wildlife health also plays a vital role by restricting as much as possible human-wildlife contact in facilitating transmission [98]. International collaboration can be described as a need that should be given prime importance while dealing with the nature of Mpox outbreaks. Governments, non-governmental organizations, and such crucial global health agencies as the WHO can team up to provide all resources, standardise all procedures, and timely respond to emerging threats. Collaborative research, specifically clade-specific dynamics, could provide essential insights into Mpox transmission and inform evidence-based policies. Outbreaks of Mpox require multifaceted strategies for containment in the short and long run. Investments that focus not only on surveillance, vaccination, and community engagement but also on international cooperation, can help lower the global burden of Mpox and prevent future outbreaks [99].

Vaccination efforts and their effectiveness against different clades

Vaccination has been a critical part of the global response to MPXV outbreaks, providing an essential tool for prevention of transmission and disease mitigation. Variation in vaccine efficacy among different MPXV clades results in these differences mainly because of variance in viral genetics and epidemiological contexts, underscoring the necessity of stratified immunisation approaches. The recent re-emergence of Mpox in non-endemic regions amplifies the scope for enhanced access to vaccines and optimised strategies for deployment as part of the response to emerging and evolving transmission dynamics. The two most used primary vaccines against MPXV are the MVA platform vaccines, initially developed for smallpox. MVA-BN (Imvanex in Europe, JYNNEOS in the US, and Imvamune in Canada) are among such vaccines that, based on their genetic similarity with Orthopoxviruses, have cross-protection against MPXV. These vaccines were demonstrated to be effective in preventing Mpox infection in both clinical and observational studies by significantly reducing the disease's severity. Their safety profile, less likely to cause adverse events than older versions of the smallpox vaccines, makes them suitable for use in a broader population, even among immunocompromised people [100, 101]. Evidence regarding their effectiveness is well-documented for both Clade I and Clade II. However, the differences in virulence and transmission dynamics between the clades will influence vaccine outcomes. Lastly, Clade I is more virulent and associated with higher case fatality rates, thus posing a more significant challenge for outbreak containment in endemic regions of Central Africa. The available vaccine supply, weak healthcare infrastructures, and delayed detection of an outbreak are among the logistical limitations of vaccination efforts in these settings. However, targeted campaigns like ring vaccination have effectively contained Clade I transmission by creating protective buffers around confirmed cases and their contacts [102, 103]. The strategies for the vaccination campaigns for Clade II, especially subclade IIb, which has been responsible for recent global outbreaks, have focused on the high-risk population in non-endemic regions. The MVA-based vaccines rolled out for the 2022–2024 outbreaks provided essential protection for healthcare workers, laboratory personnel, and exposed populations. Ring vaccination strategies coupled with PrEP for the risky cohorts did help to reduce transmission [104]. However, Clade IIb was disseminated mainly because of international travel and intimate social networks, and it was clear that large-scale efforts to vaccinate were necessary [105]. The emergence of Clade Ib will also pose a new set of questions about the effectiveness of the vaccine since the subclade harbours novel genetic characteristics, which might shape the immune responses. Preliminary data suggest that MVA-based vaccines remain effective against Clade Ib. Still, additional studies are underway to confirm this finding and ensure the vaccines remain potent against emerging lineages [47]. Despite their proven effectiveness, many obstacles have stood in the way of successful immunisation campaigns. In endemic countries, vaccine acceptance, logistics, and cold chain capacity limit the widespread implementation of immunisation programs. In non-endemic countries, rapid vaccine production and distribution scale-up during outbreaks have highlighted global preparedness gaps. In addition, unequal access to vaccines, especially between high-income and low-income countries, exacerbates the inequitable distribution of protection [106]. Another concern on the horizon is the waning immunity in decades-old individuals immunized against smallpox. While cross-immunity from vaccination against smallpox provides a degree of immunity against MPXV, immune studies indicate immunity wanes much more substantially between 20 and 30 years, which would leave much of the adult community at risk. This immunodeficiency gap has possibly fuelled outbreaks of Clade IIb infections and needs consideration when planning boosters or differential re-vaccination programs to high-risk communities [107, 108]. International cooperation is the only way to address these challenges. The expansion of vaccine manufacturing capacity, improvement of distribution networks, and investment in global stockpiles will enhance the availability of vaccines during outbreaks. In addition, integration of Mpox vaccination into broader immunisation programs, such as those against other Orthopoxviruses, can make efforts easier and improve public acceptance. Vaccination will remain an essential tool for managing Mpox, as it will protect against all clades and prevent serious outcomes among high-risk individuals. As the pathogen continues to evolve, continued investment in vaccine research and development, manufacturing and distribution will be necessary to reduce the disease's global burden and prevent future outbreaks.

Global health responses to recent outbreaks

The global health system's response to Mpox outbreaks has transformed drastically, especially considering the first-of-its-kind global spread of Clade IIb in 2022–2024. Such outbreaks have exceeded 100 countries and led to over 85,000 confirmed cases; they sparked collective international actions on containment, mitigation, and prevention. In turn, such responses highlighted the strengths and weaknesses of the global health systems, which remain critical for further preparedness and equity [109]. The WHO played a central role in coordinating the international response. The WHO declared Mpox a Public Health Emergency of International Concern in July 2022, thus mobilising resources and urging member states to implement containment measures. It called for the implementation of strengthened surveillance, case detection, and reporting to gain an all-rounded view of the size and dynamics of the outbreak. The WHO also put out interim guidelines on clinical management, infection prevention, and vaccination, which countries quickly adopted if they were already affected [110]. At the national level, governments took various approaches that differed according to the epidemiological settings in each country. Countries with strong health infrastructures, including the United States and those in Europe, ramped up quickly on diagnostic capacity, started mass vaccination campaigns, and communicated through public awareness messages. For instance, the U.S. Centre for Disease Control and Prevention partnered with state and local health departments to conduct mass immunisation drives, mainly focusing on MSM groups who happened to be primarily impacted during those outbreaks. Contrary to this, resource-constrained countries had some real difficulties with such initiatives across the globe, indicating significant disparities in preparing and responding to such outbreaks [65, 111, 112]. Mass vaccination campaigns were implemented as one of the central response strategies. MVA-based vaccines, including Jynneos, have been deployed to immunise high-risk populations and health workers. Ring vaccination strategies, based on contact tracing and vaccination of contacts, have been a core strategy of this response. However, vaccine supply bottlenecks and inequitable distribution have prevented the broader spread of coverage in most parts of endemic regions of Central and West Africa [113]. Public awareness campaigns were critical in fostering community engagement and reducing the stigma associated with Mpox. Governments and NGOs launched targeted messaging to educate the public about transmission routes, symptoms, and prevention measures. In non-endemic areas, these activities played a key role in dispelling misconceptions about Mpox and encouraging timely medical care-seeking. However, stigma and misinformation, especially regarding the disproportionate impact on MSM communities, sometimes hindered outreach efforts and underscored the need for culturally sensitive communication strategies [114]. Mpox outbreaks have underscored the significance of international collaboration and resource sharing. Logistical and financial support from organisations like Médecins Sans Frontières and the Global Fund supplemented outbreak response in resource-constrained settings. Collaborative research initiatives, including genomic surveillance projects, rapidly identified Clade IIb mutations and enhanced knowledge of the virus's global spread. These partnerships proved the worth of collaborative global action to address transboundary health threats. Despite these achievements, the Mpox response showed critical gaps in global health preparedness. Low capacity for diagnostics in endemic areas, delayed case detection, and disruptions in vaccine supply chains furthered inequities in access. Further, the lack of integrated surveillance systems monitoring zoonotic spillover and human-to-human transmission prevented early detection and rapid response [115]. To build on the future responses, several key lessons must be applied. Investment in global health infrastructure, such as expanding diagnostic networks and vaccine manufacturing capacity, will ensure that critical resources are equitably accessed. Strengthening surveillance systems, especially at the human-animal interface, will allow for earlier detection of potential outbreaks. Further collaboration between international agencies, governments, and local communities can improve the effectiveness of outbreak response efforts. The Mpox outbreaks of 2022–2024 remind the world that global health is interlinked and requires continued investments in preparedness and response capacities. Addressing the gaps highlighted by these outbreaks will strengthen the resilience of the global community against future public health threats and help to reduce the impact of emerging infectious diseases.

Future directions in Mpox research

Gaps in current knowledge and research needs

Despite the scientific progress related to the monkeypox virus, several significant critical gaps persist, impairing further epidemics' prediction, prevention, and control. Further, research that addresses such knowledge gaps should enhance the public health approach and reduce the global implications of Mpox. Critical knowledge gaps related to MPXV ecology and its reservoirs persist. In rodents and non-human primates, the virus tends to be considered a primary reservoir. However, all other species capable of harbouring and transmitting the virus remain unclear. Identifying reservoirs and their geographic distribution concerning human populations is necessary to illustrate areas at risk of zoonotic spillovers. Besides this, the environmental persistence of MPXV and factors determining survival in diverse ecosystems are very poor, thereby challenging the attempt to predict outbreaks in endemic areas. Another central area of uncertainty is the mechanisms by which clade-specific differences regarding virulence and transmission are generated. Although Clade I is better known for higher case fatality rates and Clade IIb for increased human-to-human transmissibility, there is inadequate characterisation of these differences' genetic and molecular basis. How specific mutations influence viral replication, immune evasion, and host adaptation can provide critical information on the evolutionary and epidemiologic processes at work in MPXV (Fig. 4). The emergence of Clade Ib indicates the necessity for increased genomic surveillance to identify and track new lineages (Fig. 4). Real-time sequencing during outbreaks can identify mutations associated with changes in virulence or transmissibility, making outbreak management more effective. However, integrating genomic data with epidemiological and clinical data is still very limited, and it prevents a holistic understanding of how genetic variations influence disease outcomes. Clinically, there remain gaps in characterisation, especially in atypical presentation. The various outbreaks worldwide during 2022–2024 unveiled different symptomatologies, particularly with genital and perianal lesions from Clade IIb infections. Such atypical presentations make the diagnosis challenging, which may then lead to misclassification or underreporting. More research must be done to know the full extent of clinical manifestation and its relevance to viral clades, host factors, and comorbidities. Diagnostic challenges remain a focus area for research, especially in resource-constrained settings. Even though PCR remains the gold standard for the detection of MPXV, it still depends on high laboratory infrastructure that may not be accessible in endemic areas. Affordable, portable, and sensitive point-of-care diagnostics need to be developed urgently. Another imperative tool will differentiate MPXV clades from related Orthopoxviruses to ascertain correct case identification and surveillance.

Fig. 4.

Lineage distribution of Mpox (as of 13 Apr 2025), GISAID (gisaid.org)

Vaguely, areas of unresolved research are also left for vaccination and therapeutics. For instance, though MVA-based vaccines against MPXV have shown success, the level and duration of immunity remain elusive. There is a need for studies on the efficacy of these vaccines against emerging clades, as seen with the emergence of the Clade Ib. Similarly, the availability of drugs like tecovirimat presents an area requiring further research about its efficacy cross-clade-wise and the drug's potential towards resistance. Expanding clinical trials to include a diverse population and endemic regions will provide more holistic data to inform treatment protocols. Finally, there is an absence of concentration on the socioeconomic impacts of Mpox outbreaks and the barriers to effective public health responses. For example, factors such as stigma, misinformation, and inequities in access to healthcare services disproportionately affect vulnerable populations, especially in endemic regions. Research on the behavioural and societal dimensions of Mpox outbreaks can inform strategies for community engagement, risk communication, and health equity. The above gaps call for a multidisciplinary approach involving virology, epidemiology, clinical medicine, and social sciences. Increased cooperation among governments, research institutions, and international organizations will be critical to developing a robust evidence base to inform policy and practice. Investment in research to fill these knowledge gaps will strengthen global preparedness for future Mpox outbreaks and reduce the burden of this emerging infectious disease.

Potential for emerging clades and their implications

The potential for the emergence of new clades of MPXV constitutes a serious challenge to public health, reflecting the dynamic nature of the virus and its ability to adapt to changing ecological and epidemiological conditions. The recently discovered Clade Ib and disseminated Clade IIb globally also illustrate the virus's capabilities for evolution, with the consequences put into question regarding future implications for disease transmissibility, virulence, and management at the outbreak point. MPXV evolution is supported by selective pressure, such as zoonotic transmission, human-to-human transmission, and other possible interventions, including antiviral treatments and vaccines. Genetic mutations that enhance viral fitness, such as increased transmissibility or immune evasion, could lead to new clades with distinctive epidemiological features. For example, mutations in Clade IIb enhanced its ability to maintain human-to-human transmission, allowing it to spread rapidly in non-endemic regions during the 2022–2024 outbreaks. Such evolutionary paths could lead to clades with increased transmissibility or different clinical presentations, making detection and control more challenging. One of the major concerns is the potential for increased virulence in emerging clades. Although Clade II infections are generally milder than those caused by Clade I, future clades may acquire mutations that enhance their pathogenicity, leading to more severe clinical outcomes. Such changes could worsen the burden on healthcare systems, especially in resource-limited settings where access to advanced care is already constrained. Monitoring virulence markers through genomic surveillance is essential for the early identification of these changes and preparing appropriate clinical responses. Some clades could express new antigens and thus might be antigenically different, thus reducing vaccine effectiveness. All vaccines using the attenuated vaccinia virus strain Ankara are based on cross-protection against conserved Orthopoxvirus antigens. Therefore, mutations within viral proteins would likely lead to antigenic drift, which might decrease vaccine-induced immunity and will probably demand new vaccine preparations. Clades showing antigenic differences also influence serological diagnostics, in which adaptation would be required for continued relevance. Ecological changes are also likely to contribute to the development of new clades. Habitat destruction, urbanisation, and climate change drive humans into increased contact with wildlife, thus creating an opportunity for cross-species transmissions and viral recombination. MPXV co-infections in Orthopoxvirus-infected animal reservoirs can create the backdrop for genetic exchange that has the potential to generate novel viral properties with recombinant viruses. These scenarios highlight the significance of wildlife monitoring and ecological conservation in mitigating risks associated with emerging clades. The new clades imply socioeconomic impacts as well. New clades with higher transmissibility or atypical presentations may result in larger, more frequent outbreaks that burden the healthcare systems and disrupt economies. In non-endemic regions, public health responses would face the challenges of stigma, misinformation, and vaccine hesitancy, all of which could hamper containment efforts. In endemic regions, the emergence of more virulent clades would worsen existing health disparities, disproportionately affecting vulnerable populations with limited access to medical care. The risks associated with the emergence of new clades require a proactive and integrated approach. Genomic surveillance is essential for mutational changes that may herald the emergence of new clades so these can be detected early for intervention and containment. Investment in research to understand evolutionary pathways in MPXV can inform predictive models of emergence for clades and thereby guide the development of targeted diagnostics, vaccines, and therapeutics. In addition, global cooperation and resource sharing would ensure that each country is sufficiently prepared to meet the emerging threat, regardless of its economic capacity or healthcare readiness. The emergence of new clades is a dynamic and constantly evolving challenge in Mpox management. Through prioritising surveillance, research, and preparedness, the global health community can mitigate the risks associated with these developments and protect against the unpredictable consequences of MPXV evolution.

Recommendations for surveillance and monitoring

Effective surveillance and monitoring are foundational to controlling MPXV and mitigating its impact. Against the increasing complexity of Mpox epidemiology arising from emerging clades and a global spread of the virus, strengthening surveillance is essential to enable detection at an earlier stage, guide appropriate intervention strategies, and prevent recurrence. Genomic surveillance should, therefore, be integrated with routine Mpox monitoring activities. Whole-genome sequencing of MPXV isolates will offer important information on the evolutionary dynamics, clade differentiation, and mutation patterns. These data are essential for monitoring the emergence of new clades, such as Clade Ib, and for identifying genetic changes that confer altered virulence, transmissibility, or vaccine escape. Such investments in sequencing infrastructure should target resource-limited settings where endemic transmission is most common. Portable sequencing platforms, such as the Oxford Nanopore Technologies' MinION, have provided scalable solutions for field-based genomic surveillance in such regions. Surveillance of MPXV will also involve tracking the reservoirs and environment. Strengthening wildlife health surveillance systems might inform changes in distribution and infection rates within reservoir species like rodents and nonhuman primates. Ecological research on habitat destruction, climatic change, and human interface with wildlife should be the first signs of spillover events. Creating a holistic understanding of zoonotic transmission pathways requires collaborative programs among ecologists, veterinarians, and public health experts. Expanding syndromic surveillance is critical to capture early signals of Mpox outbreaks in endemic and non-endemic regions. Syndromic surveillance systems are based on real-time data collection and analysis of symptoms consistent with Mpox, such as fever, rash, and lymphadenopathy. Leverage digital health technologies, such as mobile apps and electronic health records, to enable data collection faster and more accurately in remote and underserved locations. Public health education campaigns targeted at providers on the presentation of Mpox, including those with atypical presentations, could also improve the detection of cases. Integrated One Health approaches will be instrumental in the Mpox surveillance, considering the interlinked nature of human, animal, and environmental health. It ensures the veterinary, environmental, and human health sectors are coordinated in surveillance systems to catch all points of data origin, hence providing an inclusive understanding of MPXV dynamics during transmission. Cross-sector cooperation supports fast response strategies for wildlife vaccination or habitat conservation for zoonotic spillovers. Investments in point-of-care testing and decentralised laboratory capacity are required to address MPXV's diagnostic challenges. Affordable and portable diagnostic tools such as LAMP and CRISPR-based assays can improve case confirmation in resource-limited settings. The multiplex diagnostics will be crucial for diagnostic accuracy to distinguish MPXV from other Orthopoxviruses and common mimicking conditions such as varicella-zoster virus (VZV). Data sharing and international collaboration are necessary for proper surveillance and monitoring. International platforms, such as the WHO's Global Influenza Surveillance and Response System (GISRS), can be an example of a dedicated MPXV monitoring network. Such systems must ensure open data sharing for faster analysis and evidence-based decision-making. Standardised reporting protocols and digital tools to aggregate data in real time would enhance the speed and effectiveness of global responses. Equitable global coverage requires building local capacities to conduct surveillance and monitoring. Training programs for health staff, laboratorians, and field researchers will strengthen technical abilities in diagnostic testing, genomic sequencing, and epidemiologic analysis. Sustainable funding mechanisms, supported by governments and international organisations, must maintain these programs over the long term to provide similar resilience against MPXV outbreaks. Implementing these recommendations will establish a surveillance framework for MPXV, enhancing readiness for future mpox outbreaks and addressing emerging zoonotic diseases.

Conclusion

The re-emergence of Mpox as a global health issue, especially during the 2022–2024 outbreaks, highlights the need to understand its epidemiology, transmission dynamics, and detection strategies [116–118]. This review has compared MPXV clades, focusing on their distinct characteristics and implications for public health responses. Such considerable differences in virulence, transmissibility, and geographic distribution are observed in Clade I and Clade II, their subclades IIa and IIb, and the new emerging Clade Ib. Since Clade I is more virulent and results in severe clinical manifestations, this clade would require aggressive measures to contain it. In contrast, Clade IIb, with increased human-to-human transmissibility, has made it the primary cause of global outbreaks. These clade-specific differences warrant specific diagnostic approaches, treatment methods, and preventive measures. With polymerase chain reaction and next-generation sequencing allowing for real-time detection and ongoing monitoring, further advancements with tools such as CRISPR-based assays enable new ways of managing MPXV. However, barriers remain; significant challenges persist in implementing state-of-the-art diagnostics within constrained resource environments. Investment in relatively affordable, large-scale, accessible, and sustainable technologies must provide a framework for equitable global surveillance and outbreak response. Vaccination continues to be key for the prevention for Mpox. MVA-based vaccines are effective across the MPXV clades; however, newer lineages will likely demand new formulations. Campaigns during recent outbreaks have shown that targeted approaches are important, such as ring vaccination, and the emphasis on targeting those at highest risk. Equitable access to vaccines is essential to widespread protection and removal of logistical barriers. The public health approach to Mpox illustrates the interface between human, animal, and environmental health and exposes the interrelatedness of human and animal contagions. Improved surveillance, especially at the interface between humans and animals, provides an opportunity to identify potential zoonotic spillovers and monitor the evolution of MPXV. Cross-cutting coordination among governments, research institutions, and international organisations has been critical in understanding Mpox and advancing response strategies. Despite such advancements, there is still a gap in knowledge and preparedness. Therefore, clade-specific differences in virulence and transmission mechanisms of MPXV, ecological dynamics of MPXV reservoirs, and socioeconomic factors that influence outbreak responses are some of the issues worth further research. All these need integration with a multidisciplinary approach, including virology, epidemiology, clinical medicine, and social sciences. As MPXV continues to evolve, proactive investments in research, surveillance, and global health infrastructure become necessary to soften the impact of future outbreaks. The lessons from recent Mpox outbreaks provide information to addressing other emerging zoonotic diseases, highlighting the importance of global solidarity and resilience in public health. This would help the global health community to better understand Mpox and its clades, strengthen preparedness, reduce the burden of the disease, and pave the way for more effective responses to future infectious disease threats.

Abbreviation

MPXV

Monkeypox Virus

Mpox

Monkeypox (WHO-adopted term for disease caused by MPXV)

Clade Ia

Central African Monkeypox Clade (formerly Clade I)

Clade IIa/IIb/Ib

Sublineages of the West African Clade of MPXV

CFR

Case Fatality Rate

POC

Point of Care

PCR

Polymerase Chain Reaction

qPCR

Quantitative Polymerase Chain Reaction

LAMP

Loop-Mediated Isothermal Amplification

RPA

Recombinase Polymerase Amplification

NGS

Next-Generation Sequencing

CRISPR

Clustered Regularly Interspaced Short Palindromic Repeats

SHERLOCK

Specific High-sensitivity Enzymatic Reporter unLOCKing

DETECTR

DNA Endonuclease Targeted CRISPR Trans Reporter

ELISA

Enzyme-Linked Immunosorbent Assay

LFIA

Lateral Flow Immunoassay

MVA

Modified Vaccinia Ankara

MVA-BN

Modified Vaccinia Ankara—Bavarian Nordic

MSM

Men Who Have Sex with Men

PrEP

Pre-Exposure Prophylaxis

WHO

World Health Organization

CDC

Centers for Disease Control and Prevention

BSL-3

Biosafety Level 3

NHPs

Non-Human Primates

IFN

Interferon

TNF-α

Tumor Necrosis Factor Alpha

IL-1β

Interleukin 1 Beta

MHC

Major Histocompatibility Complex

AI

Artificial Intelligence

ML

Machine Learning

GISRS

Global Influenza Surveillance and Response System

Authors’ contributions

S.S, D.S, S.B.S: Conceptualization, writing original draft, S.K, GSN K.R, R.R.B: Writing original draft, Resources M.R.B, R.S, S.S, R.M: Formal analysis, Resources, N.A.G-C, J.F: Data curation, writing review and editing, V.A, A.J. R-M: writing review and editing, Supervision.

Funding

The authors did not receive a specific grant from funding agencies in the public, commercial, or not-for-profit sectors to develop this article.

Data availability

All the data are available within the manuscript. Remaining can be obtained from corresponding author on reasonable request.

Declarations

Competing interests

The authors declare no competing interests.