Targeted Wastewater Surveillance (TWS)

SARS-CoV-2 infection is frequently seen with the shedding of viral RNA in the stool and naso-oral fluid of both symptomatic and asymptomatic individuals.¹

• Untreated wastewater: waste from households or buildings (toilets, sinks, showers) as well rainwater or industrial use. Upstream testing is required (testing before it gets to a treatment plant) as the RNA from SARS-CoV-2 is what is being tested and concentrations are easier to test before RNA gets degraded by disinfecting chemicals during the first stage of filtration of watershed system.²

• Primary sludge: solids that settle out of wastewater that is removed during the first filtration stage of the water treatment facility. Sample volumes are less than that of untreated wastewater, but chemicals used in certain wastewater facilities may affect the data.²

• Grab: represents a single moment of that test and can be influenced by flow and composition. If the infection rate is high in the community, the levels of SARS-CoV-2 RNA levels may be very concentrated and not representative of entire population

• Composite: Pools multiple grab samples for a designated amount of time. Refrigeration will help with this method as all samples are mixed together, this provides continuous samples and are able to closer represent the whole population.² Usually 1 liter of wastewater or 100ml of sludge samples are used for testing.⁴

• Administration at universities know who is living in each dorm, so measuring dormitory samples enable a targeted sample that can narrow down potential lists for contact tracing, should elevated SARS-CoV-2 levels be found.

• Wastewater testing is cheaper than regularly testing each student. Once SARS-CoV-2 is found in the wastewater, administration would be informed to create a plan of action. With more and more colleges doing wastewater testing, more robust programs can be initiated in the spring. ⁴

• Taking samples, via pump, every 15 minutes over a 24-hour period allows students to be tested at all hours allowing a more precise day/time of infection⁴. To minimize follow-up tests, individual dorms would have to be monitored on a regular basis, especially if a large university has its own wastewater facility.

• Hospitals/care facilities – Targeted wastewater surveillance was used to monitor outbreaks in a hospital and detect when a larger peak and outbreaks were about to happen.⁵ In this test, RNA ⁷ was found in both liquid and solid waste, but higher concentrations of SARS-CoV-2 RNA was discovered in liquid waste.

• Although it may be difficult to decipher how many people have the SARS-CoV-2 virus in a hospital, it will be beneficial to notify other patients of outbreaks, keep designated areas non-contaminated (such as birthing centers or surgical areas), and individually test patients even if asymptomatic after being released.

• Factories, or food system production plants have workers coming in and out based on 8-hour shifts; although there will be a concentration of the same individuals’ waste in one area over a period of time, it will be more difficult to have an accurate reading on concentration of the virus. ⁶

• Targeting high-density workplaces will allow for early warning of outbreaks, allow for shift coverage, as well as allow management adequate time to provide individual testing or proper PPE.

• As with college dormitories, residents in a correctional facility are in close quarters where social distancing is difficult, yet residents are able to be tested within the same targeted wastewater surveillance to decipher if SARS-CoV-2 is present in the facility before an outbreak occurs. ⁶

• Since workers go in an out of the facility, correctional facilities have a very high risk for contracting SARS-CoV-2 and having a large outbreak.

• Students at Colorado State University worked with the Fort Collins Sanitation Department to use a pump to get waste samples and tested the data in the biochemistry department, taking test samples every 15 minutes for 24 hours.⁴ Most studies show that a minimum of three samples is required to detect wastewater trends over time. Things that can alter these numbers is the population that is being tested, the testing capacity at laboratories as well as testing workers, and a one-time sampling will not provide adequate data.²

• In a study by Thompson (2020), over 55% of the fecal samples tested positive for SARS-CoV-2 RNA up to 27.9 days from the first sign of symptoms compared to 16.7 days for respiratory tract samples. This means we have a larger testing window by using wastewater and fecal samples.

• A university setting is unable to tell who is infected since people shed different amounts of the virus at different times during the infection, and it doesn’t explain how many students may have the virus⁴. Traces of the virus linger in human waste, so if a person comes back to campus after isolation, their waste may alter the data.

• Quantitative data is still not complete, although first studies of the SARS-CoV-2 global outbreak done in April 2020 show a .02% prevalence rate (2 virus shedders per 1000 people tested).⁵

• Although a specific individual cost analysis isn't easily found in data, the major discussion regarding cost-effectiveness of WTS is that creating new testing sites and lab testing is expensive, but not as expensive as individual testing (saliva or nasal swabs). The use of previous polio wastewater testing is beneficial because equipment is already set up. ³