September 2020 - Wastewater Sampling - An Early Warning System for SARS-CoV-2
/Sampling of wastewater effluent is an effective strategy to detect the spread of the novel coronavirus (SARS-CoV-2) for certain types of facilities and institutions.
Transmission electron microscope image of SARS-CoV-2 virus particles. Credit: National Institute of Allergy and Infectious Diseases
Sampling of wastewater effluent is an emerging strategy to detect and prevent the spread of the novel coronavirus (SARS-CoV-2). As we look to reopen the economy and get people back to work, implementing proactive solutions that ensure the safety of employees, customers, and their families should be a top priority for all facilities. Many businesses and institutions have already begun taking steps to ensure worker and customer safety as part of their COVID-19 prevention and risk reduction strategy, including clear policies for staff and residents regarding social distancing, face coverings, disinfecting surfaces, and isolation/quarantine; use of BMPs for general cleaning and disinfecting common surfaces; and daily wellness checks including questionnaires and body temperature scans.
The effectiveness of these prevention and risk reduction measures can be improved when supported by analytical data such as regular testing of individuals for COVID-19. However, broad testing programs may not be practical or available for a variety of reasons. In the absence of this data, analyzing facility wastewater effluent for the presence of the SARS-CoV-2 virus can be an effective tool to obtain analytical data on the presence of COVID-19 at a facility. Through regular wastewater testing and monitoring, facilities and institutions may have an early warning indicator of the potential presence of the virus within the facility population or sub-populations, and have the opportunity to tailor or strengthen their preventive mitigation strategies to reduce the risk of an outbreak. A critical benefit of wastewater sampling is that it can also detect the presence of asymptomatic individuals within the population who may otherwise have gone undetected.
A Long History in Public Health
Environmental surveillance by testing of wastewater for evidence of pathogens has a long history of use in public health. In the context of the ongoing COVID-19 pandemic, it is being used for the detection of SARS-CoV-2 shed into wastewater from the upper gastrointestinal and upper respiratory system and via feces. Several studies have demonstrated that increases in SARS-CoV-2 ribonucleic acid (RNA) can be detected in environmental wastewater samples several days before detection of COVID-19 through clinical surveillance and prior to the onset of symptoms in infected persons.
Approach to Sampling
Performing periodic sampling of effluent wastewater can be a critical part of an early warning system to detect the presence of infected individuals at the facility, institution, campus, or community level.
Based on our wastewater sampling experience, we recommend that wastewater be collected through composite sampling over a 24-hour period, using an automated sampler (e.g., ISCO or equivalent). It is critical to work with your facility maintenance personnel and engineers to identify a suitable location where the sampling can be performed. Ideally, the sampling point should be the furthest downstream location prior to the wastewater exiting the site or connecting to an external sewer main. Larger institutions may establish multiple sampling points, each collecting wastewater from a specific portion of the overall facility.
Once collected, it is critical that the sample be properly labeled, packaged, and shipped on ice to the laboratory under chain-of-custody procedures. We recommend asking the laboratory to analyze the sample for the presence of SARS-CoV-2 RNA using a polymerase chain reaction (PCR) test. PCR testing is the laboratory analysis of choice as it is the most sensitive way to detect the virus. Laboratory test results are typically available within 48 hours.
As the new academic year moves forward, wastewater sampling has been used at several colleges and universities across the U.S. Refer to the links below for more information.
How to Use Sampling Results
The laboratory data will provide a semi-quantitative analysis capable of indicating relative levels of infection. As the results will only represent a “snapshot in time” of the wastewater sampling, it is recommended that wastewater sampling be conducted on a regular basis (e.g., weekly or monthly), together with daily employee wellness checks and other methods currently employed at the facility.
PHE staff sampling wastewater at a military installation during pre-COVID times.
While one-time wastewater sampling can reveal the presence or absence of infections at the facility, routine, ongoing sampling can provide additional information on infection trends. This information can be used by facility managers to determine appropriate steps in terms of mitigation measures depending upon circumstances. For example, additional health screening and COVID-19 testing could be deployed in the short-term; additional wastewater sampling could be conducted at upstream points to determine if the presence is isolated to a specific building or section; surface testing could be conducted to determine the effectiveness of existing disinfection procedures; or other steps could be considered.
Since the SARS-CoV-2 virus can be detected in wastewater at the earliest stages of infection, potentially even before infected individuals develop symptoms, the data can be used by institutional facilities as an early warning system. The presence of infected persons onsite can be discovered, even before onset of symptoms and prior to the individuals becoming contagious. Individual testing can then be performed immediately, and infected persons can be identified and quarantined.
Who Should Consider Wastewater Testing?
Wastewater sampling for SARS-CoV-2 will be most effective at a facility where the population is fairly constant and consistent. Conversely, wastewater sampling will likely be less effective at a facility or institution with a transient or highly variable population. At such facilities, other prevention and risk reduction strategies would be more effective, such as strict disinfection procedures and regular wellness checks.
Until a vaccine is developed, the best strategy we have in the fight against the spread of COVID-19 is an effective combination of prevention and mitigation strategies, as well as early detection. Wastewater sampling can provide vital information to supplement personal testing data and may give your facility a head start.
Don’t Let Opportunities for Early Detection Go To Waste!
Effective COVID-19 policies, prevention, and mitigation are an important part of ensuring the well-being of facility and institution residents, workers and visitors, and of reducing potential effects to their institution’s mission. An effective wastewater surveillance program for SARS-CoV-2 can serve as an early warning system for the presence of COVID-19 in facility populations or sub-populations. Armed with this valuable, near real-time data, facility managers and health officials can make timely and informed decisions for managing potential COVID-19 infections and reducing the effects at their facilities.
PHE has been providing environmental and health & safety related consulting services, including wastewater and other sampling, to large facilities and institutions for more than 30 years. If you have any questions on this article or would like more information related to wastewater sampling or other COVID-19-related services, please contact Chris Rua, Senior Scientist, at chrisr@phe.com.
