As the world enters year three of the coronavirus pandemic, disease trackers are trying to stay a step ahead of the constantly evolving virus by hunting it in wastewater. The CDC launched the National Wastewater Surveillance System in September 2020 in response to the pandemic. CDC created NWSS to build the nation’s ability to track COVID-19 in wastewater samples collected across the country.
Where can we fine the viruses secrets? The virus is hiding its secrets in our wastewater. Most infected people shed tiny pieces of virus when they use the bathroom. These tiny pieces of the virus contain genetic material. Scientist found this genetic material in community wastewater. Wastewater treatment plants are where samples are collected. After collection the samples are sent out for testing. Only qualified laboratories may analyze this data. Most qualified facilities are environmental or public health laboratories. Regularly testing wastewater from treatment plants allows scientists to measure when levels are rising or falling. The presence of the virus is identified faster than traditional testing alone. On average four to six days faster than traditional testing. The NWSS system analyzes the data and reports results to the health department for use in their COVID-19 response. The results are available to the public through CDC’s COVID Data Tracker.
Is Wastewater Surveillance New Technology?
Monitoring wastewater for the presence of infectious pathogens has a history of use in public health. The CDC developed wastewater surveillance as a population wide tool. This estimates the consumption or exposure of chemicals and the occurrence of infectious diseases such as Poliovirus and Hepatitis A virus for several decades. With the pervious viral tracking sucess of wastewater surveillance the CDC wanted to see if it would work for COVID-19 as well. Collecting and analyzing wastewater samples for the overall amount of viral particles present can help inform public health about the level of viral spread within a community. Current COVID-19 detection systems in conjunction with wastewater testing will give the best result. The exact number positive cases will remain unknown. However, it can provide the overall trend of virus concentration within that community.
Wastewater Surveillance Advantages
Wastewater surveillance has many advantages. It is anonymous. It is efficient. Instead of an individual test, a single wastewater sample tests a population that could represent millions of people. Its efficiency also makes it more cost-effective. The average price for a single PCR-based coronavirus test at a U.S. hospital is about $140. While the cost for a lab to analyze a wastewater sample representing a whole community is only about $300. Wastewater sampling detects the virus in people who have no symptoms. Sampling can be done if there is public sewage system.
Wastewater Surveillance Limitations
But even as wastewater monitoring takes on greater importance in some parts of the country. Using this data as a national surveillance system faces obstacles. Wastewater surveillance for viral detection is still a developing field. It is not possible to predict the total number of infected individuals reliably and accurately in a community based on sewage surveillance alone. Wastewater surveillance will not represent homes or businesses on septic-based systems. It will not represent communities or facilities treat their own waste, such as prisons, universities, and hospitals.
The CDC system is only partially in place. Less than half of states consistently report data to the agency. Some states only have one or two sites that are active. Setting up a monitoring system is not a simple process. Even with funding from the CDC, the monitoring programs take time, labor, equipment, and coordination with wastewater treatment plants.
How The National Wastewater Surveillance System Works
Samples are collected several times during the week. A laboratory receives the samples for further processing. Scientists take the samples and concentrate the viral material from the wastewater. In addition, a separate review can take place to identify different variants. It usually takes a few days from collection to results. The process allows scientists to see increases in virus levels. But if sewer water tests positive for the pathogen, the data cannot determine the exact number of positive cases in the sample area. Temperature, rainfall, a big influx of tourists, even the time and distance waste spent traveling through sewer pipes can affect outcome.
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