Three decades of HIV epidemic dynamics in The Gambia: a comprehensive analysis of prevalence, incidence, and mortality trends, 1990–2024

Abstract

Background

The Gambia has experienced major HIV epidemic shifts over three decades. As a low-prevalence country, understanding epidemic trends remains crucial for health planning and resource allocation. This study provides a comprehensive analysis of 35 years of HIV prevalence, incidence, and mortality trends in The Gambia from 1990 to 2024.

Methods

We conducted epidemiological analysis using UNAIDS 2025 HIV estimates from 1990 to 2024. Temporal trends were examined across four phases. Log-linear regression estimated annual percent changes for people living with HIV (PLHIV), new infections, and AIDS deaths. Epidemic control was assessed using mortality-to-incidence and incidence-to-prevalence ratios.

Results

PLHIV increased 24-fold from 1,035 (95% CI 784–1,342) in 1990 to 25,247 (95% CI 20,945–30,216) in 2024. Adult prevalence rose from 0·18% to 1·29%. The early phase showed explosive growth (annual percent change + 30·46% for PLHIV), followed by declining incidence concurrent with treatment scale-up (− 4·40% annually 2010–2019; −7·37% annually 2020–2024). New infections peaked at 2,439 (2009), declining to 1,124 (2024). The mortality-to-incidence ratio exceeded 1·0 in 2023. Progressive feminization emerged: female-to-male prevalence ratio increased from 1·06 to 1·57 (β = 0·0133/year, p < 0·0001), with women comprising 61·3% of PLHIV. Treatment cascade performance fell substantially below 95-95-95 targets (63·7% diagnosed, 44·3% on ART, 34·9% virally suppressed), with pronounced gender gaps (men: 52·7%/27·2%/21·2% vs. women: 72·1%/55·4%/44·4%). Pediatric infections increased 284% (44→169 cases), representing 15·0% of 2024 infections.

Conclusions

Despite declining incidence, The Gambia faces critical gaps in treatment cascade, particularly among men, epidemic feminization, and persistent vertical transmission, requiring urgent gender-responsive and pediatric interventions.

Introduction

The human immunodeficiency virus (HIV) epidemic remains one of the most significant public health challenges globally, with an estimated 39.9 million people living with HIV as of 2023 [1]. Sub-Saharan Africa continues to bear the disproportionate burden of the epidemic, accounting for approximately 67% of all people living with HIV (PLHIV) globally, despite representing only 12% of the world’s population [1]. Although considerable progress has been made in expanding access to antiretroviral therapy (ART) and reducing new infections and AIDS-related deaths in many high-burden countries, substantial heterogeneity exists in epidemic trajectories across the continent [2]. The Gambia, a small West African nation with an estimated population of 2.7 million, is classified as a country with adult prevalence rate consistently below 2% [3]. However, this classification should not diminish the public health significance of HIV infection in the Gambian context. Low prevalence settings present unique epidemiological challenges, including concentrated epidemics within key populations, limited resources for comprehensive surveillance systems, and the risk of complacency in prevention and treatment efforts [4]. Understanding the temporal dynamics of HIV epidemics in low-prevalence West African countries is essential for evidence-based policy formulation, resource allocation, and program planning [5].

The Gambian HIV epidemic exhibits characteristics common to many West African countries, including a generalized epidemic pattern with a higher prevalence among women than men, heterosexual transmission as the predominant mode of transmission, and substantial geographic variation in prevalence across administrative regions [6, 7]. Previous research has documented important risk factors for HIV transmission in The Gambia, including early sexual debut, multiple concurrent partnerships, low condom use, and limited HIV knowledge, particularly among young people and women [8]. Additionally, The Gambia’s position as a transit country with high population mobility may contribute to the HIV transmission dynamics [9]. Since the first reported HIV case in The Gambia in 1986, the country has made progressive strides in HIV prevention, testing, and treatment services [3]. The Gambia adopted the World Health Organization’s (WHO) public health approach to ART scale-up in 2004, progressively expanding treatment eligibility criteria in alignment with evolving WHO guidelines [10]. The country achieved significant milestones, including the elimination of mother-to-child transmission (EMTCT) validation in 2020 and substantial increases in ART coverage among PLHIV [3]. However, challenges persist, including suboptimal viral suppression rates, late presentation to care, stigma, discrimination, and inadequate targeting of key populations [3].

Understanding long-term trends in HIV epidemic indicators is fundamental for assessing national HIV response effectiveness, identifying persistent gaps in prevention and care continua, and informing evidence-based policy decisions. Temporal trend analysis across distinct epidemic phases enables the identification of inflection points in epidemic trajectories, quantification of intervention impacts, and projection of future scenarios for strategic planning [11]. Beyond prevalence monitoring, comprehensive epidemic assessment requires examination of treatment cascade performance against international targets, evaluation of epidemic control indicators, including mortality-to-incidence ratios, and analysis of gender-specific patterns given well-documented disparities in HIV vulnerability and service access [12, 13]. While UNAIDS annual estimates are publicly available, published analyses that synthesize and interpret three decades of HIV epidemic dynamics in The Gambia through integrated frameworks including segmented trajectory analysis across four distinct epidemic phases, gender-stratified cascade performance evaluation, and comprehensive epidemic control indicators remain limited. Our analysis adds value beyond routine surveillance reporting by providing: (1) long-horizon phase-based interpretation that contextualizes trends within programmatic milestones; (2) quantification of gender-stratified cascade attrition mechanisms; and (3) integrated interpretation of epidemic control metrics (M: I and I: P ratios) within the context of treatment coverage gaps.

The present study provides a comprehensive epidemiological analysis of the 35 years of HIV epidemic trends in The Gambia (1990–2024), utilizing National AIDS Secretariat 2025 HIV aggregated data. We employed segmented trajectory analysis using log-linear regression to quantify annual percentage changes across four distinct epidemic phases: early epidemic (1990–1999), peak epidemic (2000–2009), treatment scale-up era (2010–2019), and recent progress (2020–2024). Specifically, we examined (1) temporal patterns in HIV prevalence with gender-stratified analysis and quantification of the progressive feminization of the epidemic; (2) absolute burden of PLHIV across age groups; (3) HIV incidence trajectories and epidemic control indicators including mortality-to-incidence and incidence-to-prevalence ratios; (4) treatment cascade performance (diagnosis, antiretroviral therapy coverage, viral suppression) against UNAIDS 95-95-95 targets, with detailed gender gap analysis; and (5) pediatric HIV burden including mother-to-child transmission persistence. By systematically documenting these trends using rigorous statistical methods, incorporating uncertainty quantification, and analyzing differential patterns by gender and age, this analysis addresses critical evidence gaps for HIV programming in low-prevalence settings. Our findings are directly relevant to achieving the global goal of ending AIDS as a public health threat by 2030, particularly regarding the imperative to close gender gaps in treatment access and to accelerate progress toward universal viral suppression. This analysis represents a comprehensive synthesis and interpretation of publicly available modeled estimates rather than primary data collection. Our contribution lies in the integrated epidemiological framework, rigorous statistical quantification of temporal trends, and policy-relevant interpretation that connects observed patterns to programmatic gaps and priorities for low-prevalence settings.

Methods

Study design and data source

This study employed a descriptive epidemiological design to analyze temporal trends in HIV epidemic indicators in The Gambia over a 35-year period, from 1990 to 2024. We analyzed modeled HIV estimates from the National AIDS Secretariat (NAS) HIV Estimates 2025 dataset (version released March 2025), which represents the authoritative source for national HIV surveillance in The Gambia [14]. This dataset contains UNAIDS Spectrum-generated estimates for the period 1990–2024, produced through the UNAIDS-supported national estimation process conducted in collaboration with The Gambia Ministry of Health and development partners. These estimates are generated through synthesize data from population-based surveys, antenatal clinic sentinel surveillance, HIV case reporting systems, and programmatic monitoring data on testing and treatment services. Importantly, these are modeled estimates rather than direct empirical measurements, produced through statistical modeling processes that incorporate multiple data sources and epidemiological assumptions.

Epidemic indicators and definitions

We analyzed the following key HIV epidemic indicators:

HIV prevalence The proportion of individuals living with HIV among the total population in a specified age group expressed as a percentage. We examined the prevalence among adults aged 15–49 years (overall population, women aged 15–49 years, and men aged 15–49 years). The 15–49 age range represents the standard demographic indicator used in HIV surveillance, as it captures the population at the highest risk for sexual transmission [13].

People Living with HIV (PLHIV) The absolute number of individuals estimated to be living with HIV, disaggregated by age group including children aged 0–14 years, adults aged 15 years and above, and women aged 15 years and above. These counts represent point prevalence estimates as of December 31st of each calendar year.

HIV incidence Measured as both incidence rates (expressed as a percentage among adults aged 15–49 years and per 1,000 population among all ages) and absolute numbers of new HIV infections annually. Incidence represents the number of individuals newly acquiring HIV infection during the specified calendar year divided by the person-time at risk [15].

AIDS-related mortality The number of deaths attributable to AIDS-related causes, including opportunistic infections, HIV-associated malignancies, and direct effects of HIV. Mortality estimates were examined for the total population, children aged 0–14 years, adults aged 15 years and above, and women aged 15 years and above.

Treatment cascade indicators Three sequential stages were assessed: (1) percentage of PLHIV who knew their HIV status (diagnosis), (2) percentage of PLHIV receiving antiretroviral therapy (ART coverage), and (3) percentage of PLHIV achieving viral suppression. The performance was evaluated against the UNAIDS 95-95-95 targets [16].

Epidemic control indicators Mortality-to-incidence ratio (M: I ratio, calculated as AIDS deaths divided by new infections) and incidence-to-prevalence ratio (I: P ratio, calculated as new infections divided by PLHIV, expressed as a percentage). An M: I ratio > 1·0 conventionally indicates more deaths than new infections, whereas a declining I: P ratio suggests epidemic maturation [17].

Data management and software

Data were extracted from NAS 2025 HIV estimates Excel file, containing annual estimates with point estimates and uncertainty bounds. We created multi-panel figures to display (1) PLHIV and new infections over time, (2) AIDS-related death trajectories, (3) gender-stratified prevalence trends, (4) F: M prevalence ratio evolution, (5) M: I ratio trends, (6) treatment cascade by gender, (7) pediatric HIV burden, (8) HIV incidence rates, and (9) ART coverage expansion. Segmented regression results were displayed using phase-specific color coding. All statistical analyses were conducted using R version 4·3·0 (R Foundation for Statistical Computing, Vienna, Austria).

Statistical analysis

Temporal phase definition We partitioned the 35-year observation period (1990–2024) into four epidemiologically distinct temporal phases based on inflection points in epidemic trajectories and major programmatic interventions: (1) early epidemic (1990–1999): pre-antiretroviral therapy era characterized by rapid epidemic growth; (2) peak epidemic (2000–2009): epidemic plateau with limited treatment availability; (3) scale-up era (2010–2019): marked expansion of ART programs following national treatment guidelines; and (4) recent progress (2020–2024): a contemporary period with established treatment programs. These phases were defined a priori based on the visual inspection of epidemic curves and historical knowledge of treatment program implementation timelines.

Descriptive analysis We conducted comprehensive descriptive analyses to characterize HIV epidemic indicators across the 35-year study period. For each indicator, we calculated point estimates with 95% uncertainty intervals (UI). The UNAIDS uncertainty intervals reflect parameter uncertainty in the modeling process and are derived through Monte Carlo simulation methods, with a 95% UI representing the 2·5th and 97·5th percentiles of the posterior distribution [18]. We computed absolute changes (difference between endpoint and baseline values) and relative changes (percentage change from baseline), and examined temporal trends graphically.

Segmented trajectory analysis To quantify temporal trends within each epidemic phase, we employed log-linear regression models to estimate annual percent change (APC) for PLHIV, new HIV infections, and AIDS-related deaths. For each indicator and phase, we fitted the model.

where Y represents the indicator value, β₀ is the intercept, β₁ is the slope coefficient, and ε is the error term. The APC was calculated as APC = (exp(β₁) − 1) × 100. We report phase-specific APCs with 95% confidence intervals (CI), coefficient of determination (R²), and p-values. Statistical significance was set at p < 0·05. The models were fitted separately for each temporal phase to accommodate the nonlinear epidemic trajectories. The R² values quantified the proportion of variance explained by the linear time trend within each phase.

Gender disparity analysis Gender-stratified analyses were conducted for HIV prevalence, PLHIV distribution, and treatment cascade indicators. We calculated the female-to-male (F: M) prevalence ratio as the prevalence of women divided by the prevalence of men, and the absolute gender gap as the difference in prevalence percentage points. To assess the trajectory of gender disparities, we fitted a simple linear regression model:

where β₁ represents the annual change in the F: M ratio. We report the regression coefficient (β), 95% CI, p-value, and R². Linear trend tests were conducted using ordinary least squares regression to evaluate whether the observed increase in the F: M ratio and the proportion of women among PLHIV were statistically significant over time. For the treatment cascade, we calculated stage-specific retention rates (percentage progression from one stage to the next) and overall cascade efficiency (percentage achieving viral suppression among those diagnosed) separately for women and men.

Treatment cascade analysis Treatment cascade performance was evaluated using a sequential analysis framework. The following metrics were calculated: (1) diagnosis coverage (percentage of PLHIV aware of their status), (2) ART coverage (percentage of PLHIV on treatment), and (3) viral suppression coverage (percentage of PLHIV virally suppressed). Stage-specific retention rates were calculated as follows: diagnosis-to-ART retention = (% on ART) ÷ (% diagnosed) × 100 and ART-to-suppression retention = (% suppressed) ÷ (% on ART) × 100. The overall cascade efficiency was computed as follows: (% suppressed)/(% diagnosed) × 100. Performance gaps to UNAIDS 95-95-95 targets were calculated as the difference between the achieved coverage and 95% at each stage. All cascade metrics were stratified by sex to identify differential performance patterns.

Epidemic control indicators We computed two key epidemic control indicators for the entire study period. The mortality-to-incidence (M: I) ratio was calculated annually as total AIDS-related deaths divided by total new HIV infections, with values > 1·0 indicating deaths exceeding new infections. The incidence-to-prevalence (I: P) ratio was calculated as (new infections ÷ PLHIV) × 100, with declining values indicating epidemic maturation. HIV incidence rates per 1,000 population were calculated as (new infections ÷ total population) × 1,000 to account for population growth over time.

Pediatric HIV analysis We examined pediatric HIV indicators (children aged 0–14 years), including the absolute numbers and proportions of pediatric PLHIV, new pediatric infections, and pediatric AIDS deaths. The pediatric proportion of the total epidemic burden was calculated as follows: (pediatric PLHIV ÷ total PLHIV) × 100. The pediatric infection proportion was calculated as (pediatric new infections ÷ total new infections) × 100 to assess mother-to-child transmission persistence. The crude pediatric mortality rate was estimated as (pediatric deaths ÷ pediatric PLHIV) × 100 per 100 child-years.

Ethical considerations

This study utilized publicly available aggregated national estimates from NAS, which do not contain individual-level identifiable information. Therefore, institutional review board approval was not required. The country’s estimates are produced through a collaborative process with national HIV programs and are intended for public health monitoring and policy development purposes.

Results

From 1990 to 2024, The Gambia experienced substantial changes in the dynamics of the HIV epidemic. The analysis encompassed 35 years of national HIV estimates, documenting a trajectory of 25,247 PLHIV in 2024, representing a 24-fold increase from 1,035 in 1990. This analysis examined epidemic trajectories, gender disparities, treatment cascade performance, and epidemic control indicators across four distinct temporal phases.

Epidemic trajectory and temporal trends

Overall epidemic growth

The HIV epidemic in The Gambia demonstrated exponential growth over a 35-year observation period (Fig. 1A). PLHIV increased from 1,035 (95% CI 784–1,342) in 1990 to 25,247 (95% CI 20,945–30,216) in 2024, representing a 2,340% increase. Adult HIV prevalence (ages 15–49 years) rose from 0·18% (95% CI 0·14–0·23%) in 1990 to 1·29% (95% CI 1·07–1·54%) in 2024, a 607% relative increase (Table 1).

Fig. 1.

Epidemic trajectory and temporal trends of HIV in The Gambia, 1990–2024. Panel A: PLHIV and new infections over time: Solid blue line represents people living with HIV (left y-axis), dashed red line represents new HIV infections (right y-axis). Shaded areas indicate 95% uncertainty intervals. Panel B: AIDS-related deaths: Purple line shows annual AIDS-related deaths with 95% uncertainty interval (shaded area). Panel C: Mortality-to-incidence ratio: Red area represents the M: I ratio over time (pre-threshold). Green shaded region (M: I > 1.0) indicates the period where deaths exceeded new infections, conventionally interpreted as epidemic control threshold. Panel D: Epidemic phases (1990–2024): Four color-coded epidemic phases showing PLHIV trajectory: Early Phase (1990–1999, light blue), Peak Phase (2000–2009, light green), Scale-up Era (2010–2019, light yellow), Recent Progress (2020–2024, light pink).

Table 1.

HIV epidemic indicators by temporal phase in The Gambia, 1990–2024

Period	PLHIV start	PLHIV end	PLHIV % change	Incidence start	Incidence end	Incidence % change	Deaths start	Deaths end	Deaths % change
Early epidemic (1990–1999)	1,035	11,289	991.1%	370	2,289	519.2%	41	589	1347.4%
Peak epidemic (2000–2009)	12,842	22,569	75.7%	2,394	2,439	1.9%	704	1,544	119.2%
Scale-up era (2010–2019)	23,224	26,216	12.0%	2,298	1,561	-32.1%	1,476	1,406	-4.7%
Recent progress (2020–2024)	26,168	25,247	-3.5%	1,548	1,124	-27.4%	1,419	1,192	-16.0%

PLHIV people living with HIV. Values represent point estimates at the beginning and end of each period. Incidence and deaths values are annual estimates

New HIV infections increased from 370 (95% CI 267–502) in 1990 to a peak of 2,439 (95% CI 1,891–3,154) in 2009 before declining to 1,124 (95% CI 803–1,565) in 2024 (Fig. 1A). AIDS-related deaths rose sharply from 41 (95% CI 26–61) in 1990 to 1,544 (95% CI 1,160–2,035) in 2009, and subsequently declined to 1,192 (95% CI 869–1,610) in 2024 (Fig. 1B). The mortality-to-incidence (M: I) ratio increased from 0·110 in 1990 to 1·061 in 2024, crossing the 1·0 threshold in 2023, indicating that AIDS-related deaths exceeded new infections for the first time (Fig. 1C; Table 4).

Table 4.

HIV treatment cascade performance by gender, The Gambia, 2024

Cascade stage	Overall	Women	Men	Gender gap	Gap to 95% target
Diagnosed	63.7%	72.1%	52.7%	+ 19.4pp	+ 31.3pp
On ART	44.3%	55.4%	27.2%	+ 28.2pp	+ 50.7pp
Virally suppressed	34.9%	44.4%	21.2%	+ 23.2pp	+ 60.1pp

ART antiretroviral therapy. pp percentage points. Values represent percentages of all PLHIV at each cascade stage. Gender gap calculated as women minus men (positive values favor women). UNAIDS 95-95-95 targets: 95% diagnosed, 95% on ART, 95% virally suppressed

Segmented trajectory analysis

The log-linear regression models identified four distinct epidemic phases with significantly different annual percent changes (APC) (Fig. 1D; Table 2). The early epidemic phase (1990–1999) exhibited explosive growth with an APC of + 30·46% (95% CI 5·17–61·83%; R²=0·982, p < 0·001) for PLHIV, + 22·47% (R²=0·946, p < 0·001) for new infections, and + 34·38% (R²=0·990, p < 0·001) for AIDS-related deaths. The peak epidemic phase (2000–2009) demonstrated plateau dynamics with a PLHIV APC of + 6·29% (95% CI −0·46 to 13·50%; R²=0·968), new infections APC of + 0·23% (R²=0·157, p = 0·28), and deaths APC of + 8·86% (R²=0·939). The treatment scale-up era (2010–2019), which temporally aligned with expanded ART programs, demonstrated a transition with PLHIV APC slowing to + 1·33% (95% CI −2·14 to 4·92%; R²=0·833), while new infections declined at − 4·40% annually (R²=0·966, p < 0·001) and deaths stabilized at + 0·40% annually (R²=0·077, p = 0·43). The recent progress phase (2020–2024) demonstrated accelerated improvements: PLHIV decreased by − 0·89% annually (95% CI −0·96 to − 0·82%; R²=0·999, p < 0·001), new infections declined at − 7·37% annually (R²=0·989, p < 0·001), and AIDS-related deaths decreased by − 4·57% annually (R²=0·920, p = 0·04). All phase-specific APC estimates achieved excellent model fit (R²>0·8) except for the plateau phase new infection model (R²=0·157), indicating a limited linear trend during that period.

Table 2.

Annual percent change in HIV epidemic indicators by temporal phase, The Gambia, 1990–2024

Period	PLHIV APC (%)	PLHIV 95% CI	PLHIV R2	Incidence APC (%)	Incidence R2	Deaths APC (%)	Deaths R2
Early epidemic (1990–1999)	30.46	(5.17, 61.83)	0.982	22.47	0.946	34.38	0.990
Peak epidemic (2000–2009)	6.29	(-0.46, 13.50)	0.968	0.23	0.157	8.86	0.939
Scale-up era (2010–2019)	1.33	(-2.14, 4.92)	0.833	-4.40	0.966	0.40	0.077
Recent progress (2020–2024)	-0.89	(-0.96, -0.82)	0.999	-7.37	0.989	-4.57	0.920

APC annual percentage change. PLHIV people living with HIV. CI confidence interval. R² coefficient of determination. All models used a log-linear regression. P-values < 0·05 considered statistically significant

Gender disparities in HIV prevalence

Female-to-male prevalence ratio

HIV prevalence demonstrated marked and progressive gender disparities throughout the observation period (Fig. 2A). Among adults aged 15–49 years, the prevalence of HIV in women increased from 0·19% (95% CI 0·15–0·25%) in 1990 to 1·57% (95% CI 1·30–1·88%) in 2024, representing a 740% increase. Men’s prevalence increased from 0·18% (95% CI 0·14–0·24%) to 1·00% (95% CI 0·81–1·23%), a 468% increase (Table 3). The female-to-male (F: M) prevalence ratio increased linearly from 1·06 in 1990 to 1·57 in 2024 (β = 0·0133 per year, 95% CI 0·0121–0·0145, p < 0·0001, R²=0·917), representing an increase of 0·133 per decade (Fig. 2B and C). Intermediate F: M ratios were 1·20 (2000), 1·26 (2010), and 1·50 (2020), demonstrating consistent upward trajectory. The absolute gender gap in prevalence widened from 0·01% points in 1990 to 0·57% points in 2024 (p < 0·0001 for the linear trend), indicating a systematic rather than stochastic process underlying the progressive feminization of the epidemic.

Fig. 2.

Gender disparities in HIV prevalence and epidemic feminization, The Gambia, 1990–2024. Panel A: HIV prevalence by gender (ages 15–49 years): Blue line represents women, orange line represents men. Lines show adult HIV prevalence trends with 95% uncertainty intervals. Panel B: Female-to-male prevalence ratio: Purple area shows the evolution of the F: M prevalence ratio from 1990 to 2024, with parity line at 1.0. Panel C: Gender gap in HIV prevalence: Purple area illustrates the widening absolute gender gap (percentage points difference) in HIV prevalence between women and men over time, with peak annotation. Panel D: Women as percentage of adult PLHIV: Pink area demonstrates progressive feminization of the epidemic, with women’s proportion increasing from 52.2% in 1990 to 61.3% in 2024. Parity line at 50%

Table 3.

Gender-specific HIV prevalence indicators, The Gambia, 1990–2024

Year	Women prevalence (%)	Men prevalence (%)	F: M ratio	Gender gap (pp)	Women % of PLHIV
1990	0.19	0.18	1.06	0.01	52.2%
2000	1.75	1.46	1.20	0.29	54.8%
2010	2.21	1.75	1.26	0.46	55.4%
2024	1.57	1.00	1.57	0.57	61.3%

F: M female-to-male. pp percentage points. PLHIV people living with HIV. Prevalence estimates for adults aged 15–49 years. Women % of PLHIV includes adults aged 15 + years

Distribution of PLHIV by gender

Among adults aged ≥ 15 years, women comprised an increasing proportion of PLHIV over time (Fig. 2D). Women accounted for 52·2% of adult PLHIV in 1990 (501 of 961 adults), increasing to 54·8% in 2000 (6,803 of 12,424), 55·4% in 2010 (12,291 of 22,182), and 61·3% in 2024 (14,489 of 23,651) (Table 3). The proportion of women among adult PLHIV increased linearly at 0·27% points annually (95% CI 0·25–0·29, p < 0·0001). In absolute numbers, PLHIV among women aged 15 + years increased from 501 in 1990 to 14,489 in 2024 (2,790% increase), compared to men’s increase from 459 to 9,162 (1,896% increase). This differential growth rate contributed substantially to the progressive feminization of the epidemic.

Treatment cascade performance and gender gaps

Overall cascade achievement in 2024

The treatment cascade performance in 2024 fell substantially short of the UNAIDS 95-95-95 targets across all three stages (Fig. 3A; Table 4). Among all PLHIV, 63·7% (95% CI 52·9–73·4%) knew their HIV status (gap to 95% target: −31·3% points), 44·3% (95% CI 36·8–51·2%) were receiving antiretroviral therapy (gap: −50·7% points), and 34·9% (95% CI 29·0–40·3%) achieved viral suppression (gap: −60·1% points). The cascade performance deteriorated at successive stages, demonstrating cumulative attrition. Retention from diagnosis to ART initiation was 69·5%, and that from ART to viral suppression was 78·8%. The overall cascade efficiency from diagnosis to viral suppression was 54·8%, indicating that nearly half of the diagnosed individuals failed to achieve viral suppression. Treatment coverage expanded from 8·7% in 2010 to 44·3% in 2024 (5·1-fold increase; Fig. 3B and C), although scale-up decelerated recently, with ART coverage increasing by only 2·8% points annually between 2020 and 2024 compared to 4·2% points annually between 2010 and 2015.

Fig. 3.

HIV treatment cascade performance and gender-specific retention patterns, The Gambia, 2010–2024. Panel A: Treatment cascade by gender (2024): Group bar chart showing cascade performance across three stages (Diagnosed, On ART, Virally Suppressed) for women (pink bars), men (blue bars), and overall (gray bars). Dashed horizontal line indicates UNAIDS 95% target. Panel B: ART coverage over time: Blue area shows percentage of PLHIV on ART from 2010 to 2024. Dashed line indicates 95% target. Panel C: Treatment cascade progress: Three trend lines showing temporal evolution of cascade stages from 2010 to 2024: Diagnosed (blue circles), On ART (orange squares), Virally Suppressed (green triangles). Dashed line indicates 95% target

Gender-stratified cascade analysis

Profound gender disparities existed across all cascade stages by 2024 (Fig. 3A; Table 4). Women achieved a 72·1% (95% CI 59·9–82·1%) diagnosis, compared to 52·7% (95% CI 42·5–62·7%) for men (19·4% point gap). For ART coverage, women achieved 55·4% (95% CI 46·0–64·5%), while men achieved only 27·2% (95% CI 21·9–33·1%), yielding a 28·2% point gap with the largest observed disparity. Viral suppression was achieved by 44·4% (95% CI 36·9–52·0%) of women compared to 21·2% (95% CI 17·6–25·3%) of men (23·2% point gap). The gender-specific cascade efficiency revealed differential retention patterns. Among diagnosed women, 76·8% initiated ART, compared to only 51·6% of diagnosed men, a 25·2% point difference in diagnosis-to-ART retention. However, retention from ART to viral suppression was comparable: 80·1% for women versus 77·9% for men, a minimal 2·2% point difference. This pattern indicates that men were disproportionately lost at ART initiation rather than at the diagnosis or viral load monitoring stages. Overall efficiency from diagnosis to viral suppression was 61·6% for women compared to only 40·2% for men, a 21·4% point difference. If men achieved women’s cascade performance, an estimated 2,300 additional men would be diagnosed, 3,340 would be on ART, and 2,750 would achieve viral suppression based on 2024 PLHIV estimates.

Epidemic control indicators

Mortality-to-incidence ratio

The M: I ratio progressively increased throughout the observation period (Fig. 1C; Table 5). The ratio increased from 0·110 in 1990 (41 deaths and 370 infections) to 0·294 in 2000 (704 deaths and 2,394 infections), 0·642 in 2010 (1,476 deaths and 2,298 infections), and 1·061 in 2024 (1,192 deaths and 1,124 infections). The ratio first exceeded 1·0 in 2023, marking that the first year AIDS-related deaths surpassed new HIV infections. While an M: I ratio exceeding 1·0 conventionally indicates declining epidemic burden, The Gambian context with only 44·3% ART coverage suggests that this threshold crossing reflects inadequate treatment scale-up and late presentation rather than successful epidemic control. The simultaneous observation of high mortality (1,192 deaths) and persistent incident infections (1,124 cases), despite available treatment, indicates substantial gaps in both the prevention and care continuum.

Table 5.

Epidemic control indicators, The Gambia, 1990–2024

Year	PLHIV	New infections	AIDS deaths	M: I ratio	I: P Ratio (%)	Pediatric %	ART coverage (%)
1990	1,035	370	41	0.110	35.7	7.2	N/A
2000	12,842	2,394	704	0.294	18.6	8.7	N/A
2010	23,224	2,298	1,476	0.642	9.9	10.3	8.7
2024	25,247	1,124	1,192	1.061	4.5	6.3	44.3

PLHIV people living with HIV. M: I mortality-to-incidence. I: P incidence-to-prevalence. ART antiretroviral therapy. N/A not available (ART scale-up began after 2004). Pediatric % proportion of PLHIV aged 0–14 years

Incidence-prevalence dynamics

The incidence-to-prevalence (I: P) ratio declined markedly from 35·7% in 1990 to 4·5% in 2024 (Fig. 4A; Table 5), indicating a transition from a young epidemic with high turnover to a mature epidemic with a lower incidence relative to prevalence. Intermediate I: P ratios were 18·6% (2000) and 9·9% (2010), demonstrating consistent downward trajectory. The declining I: P ratio reflects both increasing prevalence (through improved survival on ART and accumulation of prevalent cases) and decreasing incidence (through prevention efforts and treatment as prevention). However, persistence of an elevated absolute incidence (1,124 cases in 2024) despite a low I: P ratio indicates that epidemic maturation alone does not equate to epidemic control. HIV incidence rates per 1,000 population increased from 0·35 (95% CI 0·25–0·47) in 1990 to a peak of 1·28 (95% CI 0·99–1·66) in 2002, subsequently declining to 0·41 (95% CI 0·29–0·57) in 2024 (Fig. 4B). The recent incidence rate approximates the 1990 level, although with substantially higher absolute case numbers owing to population growth.

Fig. 4.

Incidence-to-prevalence ratio showing epidemic maturation, The Gambia, 1990–2024. Panel A: Incidence: Prevalence ratio: Pink area shows the declining I: P ratio from 35.7% in 1990 to 4.5% in 2024, indicating epidemic maturation. Panel B: HIV incidence rate (adults): Teal line shows HIV incidence per 1,000 population among adults aged 15–49 years, with 95% uncertainty interval

Pediatric HIV epidemic

Pediatric prevalence and transmission

Children aged 0–14 years comprised 6·3% of the total PLHIV in 2024 (1,597 of 25,247) compared to 7·2% in 1990 (74 of 1,035) (Fig. 5A; Table 5). Despite a proportional decline, the absolute number of pediatric PLHIV increased 21·6-fold over the observation period, peaking at 2,625 children in 2011 before declining to current levels. The number of new HIV infections among children increased from 44 (95% CI 28–67) in 1990 to 169 (95% CI 103–262) in 2024 in absolute terms (Fig. 5B). Several factors may contribute to this observed increase, which requires cautious interpretation: (1) substantial population growth in The Gambia over the 35-year period, increasing the baseline population at risk; (2) potential improvements in case detection and surveillance sensitivity, particularly for pediatric HIV diagnosis; (3) increased numbers of HIV-positive women of reproductive age as the epidemic matured; and (4) modeling assumptions regarding pediatric transmission dynamics. Pediatric infections represented 11·9% of all new infections in 1990 and 15·0% in 2024, which may indicate persistent vertical transmission, though alternative explanations including increased detection sensitivity and horizontal transmission among older children cannot be excluded based on these modeled estimates alone.

Fig. 5.

Pediatric HIV burden and vertical transmission persistence, The Gambia, 1990–2024. Panel A: Children (0–14) as percentage of total PLHIV: Beige area shows pediatric proportion of the epidemic, peaking at approximately 10% in the mid-2000s and declining to 6.3% by 2024. Panel B: Pediatric HIV epidemic (0–14 years): Orange line (left y-axis) shows pediatric PLHIV, dashed brown line (right y-axis) shows new pediatric infections. Both lines include 95% uncertainty intervals

Pediatric mortality trends

AIDS-related deaths among children peaked at 325 (95% CI 234–442) in 2008 and subsequently declined to 132 (95% CI 78–208) in 2024, a 59% reduction from the peak (Fig. 5B). The decline in pediatric mortality was more pronounced than the 23% decline in overall deaths from their peak (1,544 in 2009 to 1,192 in 2024), likely reflecting the prioritization of pediatric ART programs. However, the absolute number of pediatric deaths (132 in 2024) remained substantial relative to the pediatric PLHIV population, yielding a crude pediatric mortality rate of 8·3 per 100 child years of HIV infection. This elevated mortality, combined with persistent incident infections, indicates inadequate pediatric treatment coverage and incomplete PMTCT implementation.

Discussion

This comprehensive analysis of 35 years of HIV epidemic trends in The Gambia revealed a complex and evolving public health challenge characterized by substantial epidemic expansion during the 1990s and the early 2000s, followed by modest but incomplete progress toward epidemic control. Our findings demonstrate that while HIV prevalence among adults aged 15–49 years increased more than tenfold from 0.18% in 1990 to a peak of 1.90% in 2003, the prevalence has subsequently declined to 1.29% by 2024, representing a 32% reduction from peak levels. However, the absolute burden of PLHIV has increased dramatically from 770 individuals in 1990 to 25,247 in 2024, reflecting both the cumulative nature of HIV infection, with improved survival on ART, and continued incident infections. These trends underscore the persistent challenge of achieving epidemic control in low-prevalence settings, despite significant investments in HIV prevention and treatment programs.

The temporal patterns observed in The Gambia mirror broader regional trends in West Africa, where HIV epidemics have been characterized by a lower prevalence compared to Eastern and Southern Africa, but substantial heterogeneity across countries [19]. The peak in HIV prevalence around 2003 temporally corresponds with similar inflection points documented in neighboring Senegal and Guinea-Bissau, which may reflect the combined effects of epidemic maturation, mortality among untreated PLHIV, and the early impacts of prevention programs [20]. The subsequent decline in prevalence, while encouraging, has been more modest than the decline observed in high-burden countries that have achieved rapid ART scale-up and comprehensive combination prevention approaches [21]. This finding suggests that additional efforts are required to accelerate epidemic control in The Gambia, particularly through strengthened HIV testing services, improved linkage to care, and enhanced retention in treatment programs.

The persistent gender disparity in HIV prevalence, with women consistently experiencing approximately 7% higher prevalence than men throughout the study period, reflects well-documented biological, behavioral, and structural vulnerabilities that disproportionately affect women in sub-Saharan Africa [22]. These disparities can be attributed to multiple intersecting factors including age-disparate sexual partnerships, limited negotiating power for condom use, gender-based violence, economic dependence on male partners, and differential access to HIV prevention and treatment services [23]. The Gambia’s achievement in EMTCT validation in 2020 represents a significant milestone. However, addressing the broader structural determinants of women’s HIV vulnerability requires multi-sectoral interventions beyond the health sector, including economic empowerment programs, educational opportunities, legal protection against gender-based violence, and efforts to transform harmful gender norms [24].

The interpretation of pediatric HIV trends requires particular caution given data limitations. While The Gambia achieved EMTCT validation in 2020, a significant programmatic milestone, the observed absolute increase in estimated pediatric infections from 44 cases in 1990 to 169 cases in 2024 is complex and may not solely reflect PMTCT program gaps [25]. Alternative explanations merit consideration: (1) population growth resulted in approximately 3.4-fold increase in the child population over this period; (2) improved pediatric HIV case detection and diagnostic infrastructure may have increased ascertainment; (3) modeling assumptions regarding pediatric transmission dynamics may have evolved; and (4) the age range 0–14 years includes potential horizontal transmission among adolescents, not only vertical transmission in infancy.

Confirmation of PMTCT gaps would require programmatic data including PMTCT coverage among pregnant women living with HIV, maternal viral suppression rates during pregnancy and breastfeeding, early infant diagnosis coverage, and documentation of transmission timing. The persistence of any vertical transmission post-EMTCT validation represents a critical programmatic concern, but the magnitude and mechanisms require verification through cohort-level surveillance rather than reliance on modeled national estimates alone. Residual pediatric infections likely reflect multiple factors including late antenatal care presentation, suboptimal viral load suppression, inadequate adherence support, and potentially horizontal transmission, though definitive attribution requires additional epidemiological investigation [26].

While we cannot formally attribute temporal changes in incidence to specific interventions, the plateauing of HIV incidence at relatively high levels since 2010, with approximately 1,100-1,300 new infections annually, represents a critical programmatic challenge. Temporarily coinciding with expanded access to ART and despite evidence from other settings that high ART coverage can substantially reduce HIV transmission at the population level [27], The Gambia has not achieved dramatic reductions in incidence observed in settings with high ART coverage and viral suppression rates. This finding suggests potential gaps in the HIV prevention and treatment cascade, including undiagnosed HIV infections, delayed ART initiation, suboptimal adherence and retention, inadequate viral load monitoring, and the limited reach of prevention services to key populations and geographic hotspots. Mathematical modeling studies have demonstrated that achieving substantial reductions in HIV incidence requires not only high ART coverage but also high rates of viral suppression among those on treatment, typically exceeding 90% [17]. Strengthening the quality of HIV treatment programs, rather than merely expanding coverage, is essential for reducing the ongoing transmission in The Gambia.

The continued burden of AIDS-related mortality, with approximately 1,200 deaths annually in 2024, highlights persistent challenges in achieving the third 95 target of the UNAIDS Fast-Track strategy (95% of people on ART achieving viral suppression) [16]. AIDS-related deaths in the ART era are predominantly attributable to late HIV diagnosis with advanced immunosuppression, suboptimal adherence leading to virologic failure, drug resistance, and comorbidities including tuberculosis and cryptococcal meningitis [28]. Reducing AIDS-related mortality requires multifaceted interventions, including community-based HIV testing strategies to identify undiagnosed infections, rapid ART initiation protocols, enhanced adherence support, particularly during the critical first year of treatment, routine viral load monitoring with timely intervention for elevated viral loads, and improved management of opportunistic infections [29].

Strengths and limitations

Several methodological strengths enhance the confidence in our findings. The use of national comprehensive estimates, which synthesize multiple data sources through rigorous statistical modeling approaches, provides the most comprehensive assessment of national HIV epidemic trends. The 35-year observation period enabled the robust characterization of long-term epidemic dynamics and identification of temporal inflection points. Sex- and age-disaggregated analyses revealed important disparities that require targeted programmatic responses.

However, several important limitations must be acknowledged. First, this analysis relies entirely on modeled estimates rather than direct empirical surveillance or cohort data. While UNAIDS Spectrum modeling represents the standard approach for national HIV estimation and incorporates rigorous Bayesian methods, these estimates inherently carry uncertainty from multiple sources: (1) data sparsity, particularly in earlier epidemic years (1990–2000) when surveillance infrastructure was limited; (2) evolving modeling assumptions and parameter values that may have changed across the 35-year estimation period; (3) reliance on prevalence surveys with wide sampling intervals; and (4) uncertainty in key epidemiological parameters including progression rates and mortality patterns.

Second, the wide uncertainty intervals, particularly evident in earlier years, reflect substantial parameter uncertainty and should be interpreted cautiously. For example, PLHIV estimates in 1990 ranged from 784 to 1,342 (95% UI), representing a nearly 2-fold uncertainty range. Temporal changes where uncertainty intervals overlap substantially (such as year-to-year variations within epidemic phases) should not be over-interpreted as definitive trends. Third, modeled estimates cannot capture important sources of heterogeneity including subnational geographic variation, epidemic dynamics among key populations (men who have sex with men, sex workers, mobile populations), and local programmatic variations. These limitations are particularly relevant for targeted prevention efforts that require granular epidemiological intelligence beyond national averages. Fourth, our descriptive epidemiological design precludes definitive causal attribution of observed trends to specific interventions. While temporal correlations with major programmatic milestones (ART scale-up post-2004, PMTCT expansion, EMTCT validation in 2020) are suggestive and biologically plausible, our analysis cannot formally quantify intervention impacts or exclude alternative explanations including natural epidemic dynamics, changes in surveillance methodology, or evolving modeling approaches.

Policy and program implications

Looking forward, achieving the ambitious UNAIDS 2030 targets for ending AIDS as a public health threat will require renewed commitment and strategic innovations in The Gambia’s HIV response [13]. Priority areas for strengthening the national HIV program include: (1) expanding HIV testing services through community-based approaches, index testing, and self-testing to identify undiagnosed infections; (2) implementing differentiated service delivery models to improve retention in care and treatment adherence; (3) strengthening viral load monitoring systems and enhancing adherence counseling for those with elevated viral loads; (4) addressing the needs of key populations, including men who have sex with men, sex workers, and mobile populations through tailored, non-stigmatizing services; (5) integrating HIV services with other health priorities, including sexual and reproductive health, tuberculosis, and non-communicable diseases; (6) strengthening pediatric HIV programs, including: enhanced PMTCT cascade monitoring to identify transmission breakpoints, early infant diagnosis scale-up with point-of-care testing platforms, pediatric ART optimization with child-friendly formulations, retention strategies for HIV-exposed infants through the breastfeeding period, and family-centered care models that support HIV-positive mothers and their children through integrated maternal-child health platforms; and (7) addressing structural barriers, including stigma, discrimination, gender inequality, and poverty, that drive HIV vulnerability and impede access to prevention and treatment services.

Conclusions

Over 35 years, The Gambia has experienced substantial HIV epidemic expansion followed by partial control, with prevalence declining from peak levels but remaining stable at approximately 1.3% since 2010. The dramatic increase in PLHIV from fewer than 1,000 to more than 25,000 individuals reflects improved survival on ART but also continued incident infections. Persistent gender disparities, with women experiencing a higher HIV burden, underscore the need for gender-transformative interventions to address structural vulnerabilities. While achievements in PMTCT are commendable, the plateauing of HIV incidence and continued AIDS-related mortality highlights critical gaps in the prevention and treatment cascade. Ending AIDS as a public health threat in The Gambia by 2030 will require intensified efforts to achieve high testing coverage, universal treatment access, viral suppression among those on ART, and comprehensive combination prevention strategies tailored to the Gambian context. This analysis provides essential baseline data for monitoring progress toward these goals and identifying priority areas for programmatic investment and innovation.

Author contributions

AB conceptualized, designed, and conducted the analysis and wrote the background, methods, and results. AB, LFSB, AK, POB, AJ, and ESGN critically reviewed and edited the manuscript for its intellectual content. All the authors have read and agreed to submit this manuscript for publication.

Funding

This study did not receive any forms of funding.

Data availability

The National AIDS Secretariat HIV Estimates 2025 dataset analyzed in this study is available upon reasonable request from the corresponding author or National AIDS Secretariat (NAS), Office of The President, Banjul, The Gambia. The data are also accessible through the AIDSinfo UNAIDS country data portal for The Gambia.

Declarations

Consent for publication

No consent to publish was required for this study, as we did not use any details, images, or videos related to the individual participants. In addition, a secondary aggregated dataset was used in this study.

Informed consent

This study involved a secondary analysis of The Gambia 2025 HIV data/estimate data with approval from the NAS.

Competing interests

The authors declare no competing interests.