Soon after the news that the Centers for Disease Control and Prevention (CDC) and the US Department of Health and Human Services (HHS) are initiating the National Wastewater Surveillance System (NWSS) to help learn the extent of COVID-19 infections in select communities, researchers are already collecting helpful data that can predict the rise and fall of local cases. This data is intended to provide efficient and timely pooled community samples where testing is mostly unavailable.
Wastewater can be tested for the virus that causes COVID-19 as it can be shed in the feces of infected individuals and there appears to be no direct link between exposure to fecal material and viral infection. In fact, testing in this manner provides a number of advantages and can provide a boost for health officials looking for more data on the pandemic and its cures. The virus can be shed by both symptomatic and asymptomatic individuals, and because nearly 80 percent of US households are served by municipal sewage, the untreated wastewater can offer clues on changes in community infections.
An early example of this data collection can be found in Reno, Nevada, where the latest model is being utilized to help predict the rise and fall of COVID-19 cases in the coming week. Data sampled from sewers and wastewater treatment plants are exhibiting clear correlations to the total of positive tests for the virus that would follow in about one week. Researchers are considering this type of testing a leading indicator of what is happening in the surrounding community. For example, monitored sewers and wastewater facilities between April 2020 and December of the same year kept track of concentrations of the virus. According to reports, the results of the study released in late March showed an increased presence in concentrations which preceded a significant increase in confirmed cases about a week later.
Researchers believe the wastewater test data is predictive due to the fact that people most often delay testing until clear symptoms are evident. Marker concentrations measured by the tests provide real time data, or at the very moment the virus is secreted into the wastewater. But while the samples collected from the monitoring program can’t can’t isolate data related to the effects of vaccinations, wastewater-based monitoring can still provide signs if the pandemic is decreasing and the number of cases is going down.
The Reno study sampled wastewater at a dozen sewers in the area and three water reclamation facilities over the course of a week. The rise of genetic viral material became immediately evident once the October spike arrived, and the data was accurate and consistent with the data collected from the researched communities. Other researchers and health experts across the United States and Europe began their own tracking programs, measuring the trajectories of local outbreaks using flushed waste. One in one study, wastewater from a community near a meat-packing plant where employees were infected signaled an outbreak a few days before it was officially reported.
The question remains if the virus remains after being treated. Because the research was able to be conducted under the single roof of the respective wastewater treatment plants, researchers were able to observe the entire process, including both the influent and effluent. Fortunately, while the virus was clearly detected in the water when entering the plant, it was just as clearly not detected when going out, providing definitive evidence that the coronavirus cannot survive wastewater treatment.
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