Sewage tests have captured rising levels of COVID and even evidence of polio. Can you predict new viral outbreaks?
Yogi Berra said it well: “It is difficult to make predictions, especially about the future. “
While he wasn’t talking about viral infections or the current pandemic, he might as well have. Even the best scientists, infectious disease specialists and epidemiologists have struggled to accurately predict when new viral outbreaks will appear (think COVID-19), when old ones will reappear (think polio), and how to figure it out in time to make a difference. What if they could? An already available tool called wastewater testing shows promise, and how we use the results could help curb the next wave of COVID or predict the rise of a surprising new virus.
COVID: When can we expect the next excursion?
For months now, the United States has recorded more than 100,000 new cases of COVID-19 and 300 deaths everyday. And in fact, the number of cases is likely much higher because test rates have plummeted and positive home tests aren’t included in official counts. With numbers like these and new variants emerging, further spikes in cases seem inevitable.
But when?
Perhaps in the coming weeks, new highly contagious variants are spreading. Or maybe fall and winter because we spend more time indoors. Or maybe this virus will surprise us again and wait until next year to reappear.
A huge challenge in containing the COVID-19 pandemic is that by the time we know that infections are increasing rapidly in a community, it has already been going on for some time. Because people often show no symptoms initially, the infection can spread for a while without warning.
If we could predict when the next peak will occur, it is possible that we could take appropriate preventive action. And this is where your feces comes into play – feces, poop, whatever you prefer to call it.
Detection of viral outbreaks using wastewater
The idea is simple: When people have a viral infection, the virus can often be detected in the stool. Therefore, the wastewater of a city, or perhaps a community, can be tested to see if the virus is present and, if so, if the amount increases with time.
This approach has been used since the 1940s, when polio was a major concern. But wastewater tests can also be used to detect different types of hepatitis, flu-like norovirus, and possibly measles.
The methods used to test wastewater have improved over time. Early efforts attempted to grow viruses from water samples; more recently, testing has shifted to detecting viral genetic material.
Polio and COVID in wastewater
In June 2022, sewage testing in London detected the virus that causes polio, a life-threatening or disabling disease. Although no active cases of polio have yet been diagnosed in London, the discovery has launched an investigation into where the virus comes from, who may be infected and whether there is a threat to public health.
In the United States, a New York county that had tested sewage for COVID levels also began testing for polio after an active case of polio occurred in an unvaccinated adult.
Have wastewater analyzes proved useful for detecting and tracking SARS CoV2, the virus that causes COVID-19? In fact, it has. Levels of this virus in sewage closely mirrored infection rates in many cities around the world and, in some cases, predicted an outbreak before a community even noticed that cases were rising. The CDC now includes wastewater data in its regular reports on COVID-19 infection rates.
Wastewater test results are usually combined with other information, such as infection rates reported by hospitals and doctors’ offices, infection trends in neighboring communities, and vaccination rates. Together, this information provides public health officials with better information on a range of troubling viral infections and where the number of cases could be headed.
How is wastewater data useful?
Detecting the presence or increased level of the virus in wastewater can help public health officials, healthcare professionals and researchers
- predict when a power surge occurs or when it peaks
- update messages on prevention measures (for example advice on the use of the mask in public spaces or on physical distancing)
- ask for more vaccines and antiviral drugs
- encourage more testing
- identify new variants.
Letting people know if cases are increasing in their community can be especially important for those facing obstacles to testing, including people who don’t have health insurance or a primary care physician. Wastewater analyzes can be especially helpful when counting is common, such as with COVID-19.
In the future, wastewater testing could improve to the point where the site of an outbreak could be limited to a single neighborhood or residential facility such as a nursing home or prison.
The bottom line
Unfortunately, the COVID-19 pandemic is not over. And we hear alarming reports of the international spread of the virus that causes monkeypox. In the future, old viruses such as polio and measles are very likely to reappear and new pandemics to take hold.
We will need all the help we can get to keep up with these outbreaks. Some of this help will likely come from wastewater. So, strange as it may sound, what you flush down the toilet can help health officials detect – and perhaps even contain – a public health threat.
Follow me on Twitter @Rob Shmerling
