What sewage water can tell us about the spread of COVID-19

Testing for COVID-19 is still limited, and results come far too slowly to keep ahead of the pandemic. Now, dozens of cities and countries are turning to the sewers to try to figure out if COVID-19 is spreading in their community. Actually, they’re turning to Biobot Analytics, a Massachusetts-based startup that tests wastewater and raw sewage for the presence of the novel coronavirus. 

The company launched a free pilot project in June with hundreds of wastewater treatment facilities, and now some cities are becoming paying customers for regular monitoring. Biobot’s research is what’s known as wastewater epidemiology. I spoke with Dan Ackerman, who has been reporting on this for member station WGBH. He told me the science is new, but since cities are desperate to get a handle on the virus, it’s quickly gaining converts. The following is an edited transcript of our conversation.

Dan Ackerman: These studies are not yet peer-reviewed by independent experts, so take all this with a grain of salt, but there are a couple of early studies that show this wastewater data can actually be a leading indicator. So, if a city is closely monitoring what’s going on in their sewage, if they see a spike in COVID-19 in that sewage, that could give them a few days to prepare for maybe surge capacity in the hospitals or maybe institute a lockdown to stop it from spreading.

Molly Wood: Can you give us some examples of cities that have used this technology so far?

Ackerman: In Cambridge, Massachusetts, not far from where Biobot is headquartered, the public school district recently announced that their plan for the fall is to use Biobot sewage data to help monitor whether or not to continue with the in-person portion of their classes. They have named three indicators they’re going to follow, and one is how much COVID-19 is in the sewage. And if that gets above a certain threshold, that might help trigger them to close down in-person schooling and move to remote-only.

Wood: How accurate is testing sewage water in terms of estimating the spread of the virus? How do they correlate that to the number of people who might be infected?

Ackerman: The rate that an infected person excretes COVID-19 in their stool is really variable. Researchers are still a long way from getting exact numbers of infected people based on the sewage data. They’re sampling raw sewage and looking for the presence of genetic material of the coronavirus. This is quite different from clinical testing that would say whether an individual has COVID-19. Biobot is looking at city sewage in aggregate, so everyone’s waste is mixed together. And that’s a way to quickly cast a really wide net and find out how much the virus is spreading. You can get a sense of the trends of whether an outbreak is getting worse or getting better. But you still can’t nail down an exact caseload. So that is one reason that we really need to continue stepping up clinical testing efforts.

Wood: Are there other companies in this space?

Ackerman: There are a few who are starting to get into this space. But Biobot is really the leader when you look at the for-profit sector. Biobot is a spinoff from some MIT research that’s been happening over the last few years. And most of what I would call Biobot’s competitors are other academic labs — researchers working at universities. Biobot is kind of pioneering this wastewater epidemiology as a for-profit venture.

Wood: Are there any privacy concerns here, like do you have a right to your poop? Can you be identified?

Ackerman: I looked into this question …

Wood: A question for the ages, really.

Ackerman: So far, there’s not much in the way of established law on this question. I did talk to a few legal experts who said the consensus is that you lose the rights to data once you flush it into a public sewer system. So there are some ethical concerns here, like I don’t want a private company sampling the sewer right in front of my house and learning all about me. So what Biobot’s cofounder Newsha Ghaeli told me is that by company policy, they will only sample from places in the sewer network that mix the sewage from at least 4,000 people. That way, the data they get is naturally anonymized because you have thousands of people’s waste mixed together in there.

Related links: More insight from Molly Wood

Here’s Dan’s piece on Biobot and more reading about testing sewage to try to stay ahead of coronavirus infections. The thing is that testing is a lagging indicator already in this country, since most of the people who are getting tested probably already have symptoms or think they’ve been exposed.  

Research this weekend, based on a CNBC and Dynata survey of people in the U.S. who have gotten tested, shows that 40% of COVID-19 tests in the United States take so long to process that they are clinically meaningless. Meaning, they take too long to be used for contact tracing, and most people aren’t likely to quarantine while they’re waiting for the results, so they potentially keep spreading the virus. 

While we’re on the topic of data, let’s also point out that the number of actual tests being performed in the U.S. is declining, according to the COVID Tracking Project. So we might be hearing that the number of cases is going down, but — say it with me — you can’t manage what you don’t measure. 

And speaking of measuring, a reminder that last month the Trump administration directed hospitals to stop reporting daily COVID-19 data to the Centers for Disease Control and report it instead to a private company building a database within the Health and Human Services Department. The company, Pittsburgh-based TeleTracking Technologies, got a $10 million contract to build the database. But on Saturday, The New York Times reported that when Senate Democrats asked the company to detail how it is processing and collecting coronavirus data, the company declined, saying it had signed a nondisclosure agreement with the U.S. government. Senators said HHS is also not responding to questions on the topic.

When the administration first announced the switch in data reporting, doctors and public health officials objected, saying the move might reduce transparency and access to crucial data about a pandemic that continues to rage across this country and that hospitals should ideally continue to share data with the CDC as well.