Sewage water has been a key to helping researchers and public health agencies track the spread of COVID-19 for over a year. Now the CDC is opening up this information to the public by adding wastewater surveillance to its digital COVID-19 Data Tracker. 

"The information generated by wastewater surveillance offers public health officials better understanding of COVID-19 trends in communities," Dr. Amy Kirby, the CDC's team lead for the National Wastewater Surveillance system, said at a media briefing Friday. "Because increases in wastewater generally occur before corresponding increases in clinical cases, wastewater surveillance serves as an early warning system for the emergence of COVID-19 in a community.

"These data are uniquely powerful because they capture the presence of infections from people with and without symptoms. And they’re not affected by access to healthcare or availability of clinical testing." 

The tool will let users look at the virus levels in wastewater from over the last 15 days. Users can also access information about the percentage of positive tests from a certain area over the last 15 days. 

Kirby warned that there are limitations to wastewater surveillance. For example, data is scarce in areas with no sewage infrastructure. It may also not work as well in areas with transient populations.

"Additionally, wastewater surveillance cannot be used to determine whether a community is free from infections. For these reasons, wastewater surveillance is best used in combination with case-based surveillance to maximize its value."

WHY IT MATTERS 

The COVID-19 pandemic continues to spread across the U.S. Since the start of the pandemic over two years ago, there have been more than 75 million cases in the U.S., and approximately 900,000 COVID-19-related deaths, according to the CDC. Community transmission rates remain high in all 50 states.

The agency is now is pitching this new capability as a way for the public to see trends in wastewater surveillance across the country. 

"So the big news today is that the CDC data from the National Wastewater Surveillance System is available on [the] COVID Data Tracker for the first time. And the advantage of this CDC-supported dashboard is that it allows you to compare data across states directly. The data that’s available on different state-level dashboards doesn’t have the same analyses behind it, and so it’s not directly comparable the way it is on the CDC dashboard."

THE LARGER TREND 

The National Wastewater Surveillance System (NWSS) has been using sewage to track the presence of SARS-CoV-2 since September 2020. 

"The virus can then be detected in wastewater, enabling wastewater surveillance to capture presence of SARS-CoV-2 shed by people with and without symptoms. This allows wastewater surveillance to serve as an early warning that COVID-19 is spreading in a community," reads the CDC webpage.

Over the course of the pandemic, there have been many methods of tracking the COVID-19 spread. In February 2020, Buoy Health added a new coronavirus feature after teaming up with the team at digital-epidemiology tool HealthMap and the CDC. The agency has also collaborated with Apple on a screening tool and an information platform.