Environmental surface surveillance during a COVID-19 outbreak in a school community: implications for controlling indirect transmission

Abstract

Environmental surface surveillance is a valuable tool for detecting and controlling infectious diseases. During the COVID-19 pandemic, concerns have been raised regarding the potential for indirect transmission of SARS-CoV-2 via contaminated surfaces. However, few studies have evaluated environmental contamination in non-clinical settings during outbreaks. We conducted a study in a school community during a major outbreak, collecting 35 surface samples from high-traffic areas and testing them for SARS-CoV-2 RNA using RT-qPCR. Our results showed that 31.4% of samples were positive, including high-touch surfaces such as drinking fountains and washbasins. These findings emphasize the importance of environmental monitoring to identify and address specific areas for attention, and implementing such strategies can help prevent the indirect transmission of COVID-19 in various settings.

Introduction

Severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) is a highly transmissible and pathogenic virus that first emerged in late 2019 and was identified as the cause of the coronavirus disease 2019 (COVID-19) outbreak [1]. The resulting pandemic has posed significant challenges to researchers and policymakers worldwide, who have implemented public health measures like lockdowns to prevent healthcare system collapse and reduce deaths [2]. COVID-19 has had a profound impact on the world, with over 765 million confirmed cases and 6.92 million deaths globally as of May 03, 2023 [3]. Despite administering more than 13 billion vaccine doses, the pandemic continues, with new variants emerging regularly. XBB.1.16, also known as Arcturus, is the latest variant to emerge as a descendant lineage of Omicron. As of April 17, 2023, 3648 sequences of the XBB.1.16 variant have been reported in 33 countries, leading the World Health Organization (WHO) Technical Advisory Group on SARS-CoV-2 Viral Evolution (TAG-VE) to designate XBB.1.16 as a variant of interest (VOI) during their meeting on that date [4].

Environmental surface surveillance is a valuable public health tool that has been employed for the detection and mitigation of numerous infectious diseases. Indirect transmission of SARS-CoV-2 can occur when a healthy individual comes into contact with contaminated surfaces via respiratory droplets or secretions from an infected person, which are subsequently touched by the healthy person [5]. Viral transmission is facilitated by the ability of SARS-CoV-2 to remain viable and infectious on surfaces for extended periods of time, ranging from hours to days, depending on the amount of inoculum and environmental conditions [6]. Moreover, recent studies have indicated that SARS-CoV-2 can travel over greater distances than other respiratory viruses, further contributing to its potential for widespread dissemination [7]. To gain a better understanding of COVID-19, the WHO recommends prioritizing environmental surveillance as a key objective in public health efforts [8]. Environmental monitoring has emerged as a crucial component of public health surveillance [9], given its effectiveness in detecting and mitigating the spread of infectious diseases.

With the ongoing COVID-19 pandemic, it is crucial to implement measures that can prevent the spread of the virus, including monitoring environmental contamination in high-risk settings such as schools, universities, colleges, and university centers. Therefore, the objective of this study was to evaluate the presence of SARS-CoV-2 RNA during a COVID-19 outbreak at a private school located in a town with more than 120,000 inhabitants. By monitoring environmental contamination, we can better understand the risk of transmission and contribute to a safer recovery for the community. This research has important implications for public health efforts and highlights the need for continued monitoring of environmental contamination during outbreaks.

Material and methods

Ethics approval

Ethical approval for this study was obtained from Comitê de Ética para Pesquisa com Seres Humanos from the Federal University of Lavras (COEP/UFLA) by the protocol number: CAAE 43997221.6.0000.5148.

Local of study

The present study was performed at a boarding school located in the municipality of Lavras, Minas Gerais, Brazil. The establishment has a leisure and sports area, including courts, green areas, and a religious temple, in addition to cafeterias and shared bathrooms. The educational area has classrooms and large auditoriums. The dormitories are mostly shared and separated into male and female wings.

School outbreak overview

Clinical and epidemiological data were collected from all members at a private school located in the southeastern region of Brazil. A total of 291 people, including students, teachers, and staff, were tested.

On 02/22/2021, the first 14 people with suspected COVID-19 underwent an antigen test at a municipal laboratory. Biological samples were collected from all other members of the school community using nasopharyngeal swabs (277 people). The swabs were then transferred to tubes containing 3 mL of transport solutions for referral to the laboratory. Reverse transcription–polymerase chain reaction (RT–qPCR) tests for SARS-CoV-2 RNA were performed.

Patients positive for SARS-CoV-2 were isolated, and the negative ones were retested between 3 and 5 days. This procedure was repeated until all tested patients had negative results, which was achieved on 04/01/2021. Sanitary measures were immediately implemented, like the adequate use of equipment for individual protection by all employees.

Environmental swab testing

The environmental swab testing involved the collection of 35 samples from areas with high human traffic during the biggest outbreak in a school community up until the present day. The first set of samples was collected on 03/03/21, prior to any changes in the cleaning routine. The second set of samples was collected on 01/31/2021, at the conclusion of the outbreak, when all patients tested negative. To obtain these samples, we used sterile swabs soaked in phosphate-buffered saline, which were vigorously rubbed on various surfaces. The swabs were then placed into tubes containing 3 mL of transport solution. Immediately after collection, we added 140 µL of the sample with 10 µL of exogenous internal control (Segeene, Belo Horizonte, Brazil) for viral RNA extraction using the QIAmp Viral RNA Mini Kit (QIAGEN, Maryland, USA). The Allplex 2019-nCoV Assay kit – RP10243X (Segeene, Seul, South Korea – https://seegenebrazil.com.br/allplex-sars-cov-2-assay/) [10, 11] was used for one-step qPCR, with 8 µL of total RNA used for amplification. The test was considered valid if it amplified the internal control. Amplification was evaluated for 4 different targets, including 3 viral targets for SARS-CoV-2 (gene E, RdRP gene, and N gene) and the RP-V internal control. All samples that did not amplify the RP gene were excluded from our analysis. Samples were considered positive if at least one target had a cycle threshold (Ct) below 40.

Results and discussion

The outbreak was initially identified through testing 14 individuals with symptomatic presentations who sought care at a public first-aid post. All of these patients tested positive for SARS-CoV-2. Within 24 h, 42 close contacts were investigated, and 31 of them tested positive for SARS-CoV-2 using RT-qPCR. Subsequently, the remaining 235 members of the school were tested, either for the first time or as individuals who had previously tested negative. All of these individuals tested negative for SARS-CoV-2.

Overall, out of a total community population of 291 individuals, 188 (64.6%) were identified as positive for SARS-CoV-2. Furthermore, 11 environmental samples (31.4%) collected from various areas within the school, including water coolers, toilets, door handles, light switches, sofas, and the reception desk, tested positive for the presence of SARS-CoV-2 RNA (as shown in Table 1). These findings highlight the significance of conducting mass testing in advance, which helps to distinguish between infected and uninfected individuals, regardless of symptomatology. This approach is crucial in effectively managing and containing outbreaks.

Table 1.

Summary of the SARS-CoV-2 positive and negative samples

Sector	Surface sampled	RT-qPCR	Ct
Dormitory area for negative inmates
Male shared restroom	Toilet seat cover	-
Female shared restroom	Toilet seat cover	-
Male shared dormitories	Study desk	-
	Wardrobe handle	+	35,77
	Power switch	-
	Door handle	+	34,89
	Power switch	+	34,05
	Power switch	-
Female shared dormitories	Door handle	+	34,56
	Wardrobe handle	-
	Door handle	-
	Water cooler	+	31,71
Dormitory area for positive inmates
Male shared restroom	Toilet flush	+	35,64
	washbasin	+	30,89
Female shared restroom	Toilet seat cover
Male shared dormitories	Wardrobe handle	-
	Study desk	-
Female shared dormitories	Door handle	+	33,62
Education sector
Reception desk	Table	-
Hallway	sofa	-
Administrative sector
Reception desk	Service counter	+	35,73
	Keyboard	-
Sofa	Armrest	+	35,11
Female shared restroom	Door handle	-
	Service counter	-
	Door handle	-
Dining hall
Dining hall	Napkin dispenser	-
	Food service counter	-
Chairs	Chair	-
	Table	-
Male shared restroom	Door handle	+	34,37
	Toilet flush	-
Female shared restroom	Door handle	-
	Toilet flush	-
	Toilet seat cover	-

Managing a public health crisis like the SARS-CoV-2 pandemic is a complex task that our generation has never faced before. Critical safety measures such as screening, diagnostic testing, mask usage, social distancing, and increasing vaccine availability have helped restore normalcy by reducing disease incidence and complications. However, COVID-19 may continue to cause disruptions in the near future if lessons learned are not put into practice, particularly given the frequent emergence of new variants. Therefore, minimizing the potential spread of the virus requires a robust, multifaceted approach, in which pathogens are rapidly and routinely detected from individuals to their surrounding environment.

In this context, environmental surveillance emerges as a critical part of this comprehensive process, but it has not received the same attention as other important measures, such as mass testing, asymptomatic and contact tracing, and vaccines, among others. However, in our understanding, environmental surveillance can and should be used as part of a preventive approach to COVID-19, as it is for several infectious diseases.

Environmental surveillance for monitoring the presence of SARS-CoV-2 on different surfaces has been reported by some authors. Cheng and collaborators [12] collected 377 environmental surface samples from a hospital and found a 5% positivity rate for SARS-CoV-2. Zhang and collaborators [13] detected SARS-CoV-2 on university campus surfaces, indicating that routine and multidisciplinary approaches to environmental surveillance should be used to ensure the safety of academic communities. Harvey and collaborators [14] found an 8.3% positivity rate for SARS-CoV-2 by collecting samples from 348 environmental surfaces. Mihajlovski and collaborators [15] investigated 300 environmental surface samples in public areas in Las Vegas, Nevada, and found a 10.3% positivity rate for the virus. In our study, SARS-CoV-2 RNA was detected in 31.4% of the surfaces analyzed, a higher positivity rate than those presented in the aforementioned studies. This demonstrates that during an outbreak, viral circulation is high, which can contribute to transmission amplification, but not necessarily from contaminated surfaces. Although the positive RT-qPCR analysis cannot confirm whether the detected virus is viable and has the potential to cause an infection, the swab sampling method has been previously described by other authors and has also proven to be successful in detecting SARS-CoV2 in our study.

Some studies have shown that many of these viral particles present in environmental samples do not constitute viable viruses capable of promoting infection. Thus, it is important to highlight that the presence of viral RNA on surfaces is an important tool for monitoring viral circulation and the need for implementation or reinforcement of preventive measures in that environment. As shown in Table 1, viral RNA was detected in collective environments that housed uninfected children and adolescents at the time of the survey. Before the outbreak was identified, people freely circulated in all environments, often without masks. Therefore, it is possible that infected people, even asymptomatic, were present in the rooms and bathrooms of the uninfected residents.

Furthermore, despite the relatively small number of samples, it is concerning that almost 31.4% of the sampled sites were positive for the virus, particularly in high-risk areas such as drinking fountains, washbasins, and toilets, where masks are not used. In this sense, environmental disinfection was carried out, and non-pharmacological protective measures were intensified, including distancing, mask-wearing, hand hygiene, and isolation of infected individuals, which resulted in complete resolution of the outbreak after 30 days, and negative surface testing after environmental measures were implemented.

Our study’s findings corroborate those of Marshall and collaborators [16], suggesting that environmental monitoring can predict the presence of asymptomatic individuals and evaluate the effectiveness of implemented control measures. Additionally, environmental surveillance may aid in the detection of asymptomatic COVID-19 cases, thus improving outbreak control [15]. Our study revealed that the presence of coronavirus on environmental surfaces is associated with both symptomatic and asymptomatic spreaders, making it a warning sign of an outbreak. The findings of the environmental surface testing provided valuable insights that prompted the need for additional testing. In preparation for future waves of COVID-19, we recommend conducting mass tests on individuals and an assessment of areas within schools that experience high human traffic and areas where positive cases have been identified. This comprehensive evaluation aims to identify potential hotspots and facilitate targeted environmental monitoring efforts. By implementing these strategies, we can effectively mitigate the risk of indirect transmission of COVID-19 in various settings. We also recommend appropriate sanitary procedures, such as regular cleaning and disinfection of high-touch surfaces, promoting hand hygiene practices, and ensuring proper ventilation in classrooms and shared spaces. Environmental surveillance of coronavirus can serve as a crucial measure in identifying the transmission of SARS-CoV-2 and assessing the efficacy of workplace COVID-19 protocols, especially in high-risk environments such as schools and universities. Thus, it can be a useful monitoring tool to support the safe continuation of educational activities.

Funding

Research reported in this publication was supported by the Brazilian Ministry of Health and the Minas Gerais Research Foundation (FAPEMIG). VSP received a research fellowship from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (#302569/2021–9). This research was also supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior — Brasil (CAPES) — Finance Code 001.

Declarations

Ethics approval

Ethical approval for this study was obtained from the Comitê de Ética para Pesquisa com Seres Humanos from the Federal University of Lavras (COEP/UFLA) by the protocol number: CAAE 43997221.6.0000.5148.

Competing interests

The authors declare no competing interests.