Not everyone evacuates when a Category 5 hurricane is forecast, but most people will bring in the lawn furniture and stock up on supplies. Most of us would do something to mitigate damage because we know the power of high winds and rain, and that simple precautions can go a long way. Yet when we have similarly reliable data predicting the next wave of COVID-19, few of us ever hear of it, let alone know the most prudent ways to respond to protect ourselves and others.
Municipalities all over the United States, and in the Northeast in particular, have been tracking the level of SARS-CoV-2 viral material in wastewater since the beginning of the pandemic. The study of pathogens and chemicals in water, called wastewater-based epidemiology, has been used to monitor illicit drug use in communities and to track outbreaks of intestinal viruses for many years.
Early in the pandemic, researchers began to look for COVID-19 in wastewater; they not only found it there, but quickly established that the detection of the virus in wastewater is almost always a leading indicator of an increase in COVID-19 cases in a community. A recent review of studies worldwide showed that testing could show an increase in viral material in a community’s wastewater between 10 and 14 days before a new wave of infection was seen by PCR or rapid diagnostic testing.
In Spain, these data sets have been used to monitor increases in viral activity. Communities were able to quickly detect increases in viral RNA in wastewater and respond by increasing PCR testing and implementing short-term curfew measures to slow the spread of the virus.
In 2020, the Centers for Disease Control and Prevention set up the National Wastewater Surveillance System. The system collects and compiles wastewater testing data from around the country, but it does not provide wastewater testing services, nor does it release guidance based on wastewater testing results. Further investment is needed. In the interim, the CDC has dramatically scaled up wastewater coverage. In mid-December, 44 million people were covered by the CDC’s National Wastewater Surveillance System, which has now doubled to 88 million — over 1 in 4 Americans.
Of course, using wastewater testing as a real-time monitoring tool has limitations. For example, locating the exact source of an outbreak is not likely using this technique, since people travel for work and leisure, and wastewater testing sites often cover large catchment areas. For example, in the Boston area, two test points cover millions of people. However, the data from wastewater testing have reliably correlated with the onset of each of the four major waves of COVID-19 infection in the United States.
To make wastewater testing more effective, both state and local public health agencies need to implement the following policies.
Transparency. Everyone must be able to see the data and decide on their own if they are going to take precautions. If everyone can see what is coming ahead of time, they can calculate their own tolerances for personal and communal mitigation strategies.
Local and regional communication strategies. To make the best use of this data, states and local municipalities need to map and display changes in the data and explain what the changes mean for how people travel, work, and live. Communication of wastewater data should be presented in simple-to-read pandemic dashboards.
Plan ahead. When infection rates rise, states and municipalities must put advisories — not restrictions — in place. One example would be recommending indoor masking or advising vulnerable people to avoid high-risk places.
Using wastewater surveillance data to advise communities about which precautions to take puts no additional burden on individuals to comply. There are no regulatory requirements to contend with, and municipalities can self-collect these samples as they would collect other water testing samples. Costs overall will be lower than testing individuals, but of course, investment is still required. Surveilling the environment for information about population health is an aggregate measurement and puts no one’s personal health information or confidentiality at risk.
Not every small uptick in the wastewater signal means that a new wave of infection is coming, but every wave in the Northeast has been preceded by an increase in viral material in the wastewater.
Not heeding sustained increases in local COVID levels in wastewater is like ignoring a Category 5 hurricane warning. The damage may not be as great as was predicted, but damage can be mitigated. The good news is that the CDC is investing in this capacity and others to forecast future pandemics. We need to rally the data we have today to protect the vulnerable and plan for this next uptick in cases.
Catherine Klapperich is scientific director of the Boston University Clinical Testing Laboratory and a professor of biomedical engineering at Boston University. Dr. Rebecca Weintraub is an assistant professor at Harvard Medical School and director of Better Evidence at Ariadne Labs.