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The Fight Against COVID Goes To The Sewers


The Maryland Department of the Environment (MDE) is pulling together a new statewide initiative to prevent COVID-19 outbreaks in public housing facilities: sampling and testing wastewater for the virus. 

“COVID is excreted in the GI tract of individuals who are infected,” explains Dr. Adena Greenbaum of the Baltimore City Health Department. 

If you start seeing levels of COVID increase in wastewater samples, it indicates that someone in the facility has the disease and you can start taking preventative measures.

Greenbaum, the department’s assistant commissioner of the Bureau of Clinical Services, said wastewater tests would help them prevent outbreaks before they happen. 


Gov. Larry Hogan announced $1 million in CARES act funding for the project in November. MDE Assistant Secretary Suzanne Dorsey said this new testing strategy would primarily help residents in public housing and correctional facilities. 

“How do we support and engage in the most vulnerable parts of our community? How do we bring resources to parts of our community that maybe are less likely to be tested?” Dorsey said. 

In order for the test to be effective, a housing facility has to have a wastewater stream isolated from the rest of the city. 

Dorsey said they aren’t targeting other vulnerable facilities like nursing homes, whose residents and staff already get regular clinical testing. 

The facilities should also be places where people aren’t just passing through, like schools. 

“A lot of kids will say I don't use the bathroom at school,” Dorsey said. 

In Baltimore there are 15 sampling locations spread out across nine housing facilities. The Housing Authority of Baltimore City (HABC) owns most of them, and oversees the project in coordination with the city health department. 

Environmental technician David Sotelo works at Inspection Experts, Incorporated (IEI), a Columbia, MD firm contracted by MDE to collect wastewater samples. Sotelo covers all of the city’s sampling locations. He visits about five to six of them every day. 

Every day, he parks his van by a manhole at a housing facility. He hauls out bags of ice from the van and starts smashing them against the ground. 

It’s the first step in a 24-hour process for sampling wastewater for COVID-19. The ice helps keep the sample at 39.2 degrees Fahrenheit. If the sample is too warm, any traces it had of COVID-19 would die before testing. 

He dumps the ice into a cylindrical sampling unit, around a smaller jar for the wastewater. After opening the manhole with a magnetic manhole opener, he purges the tubing going from the unit to the wastewater, and lowers the unit into the manhole. 

It takes about a half hour to set up a sampling unit, then Sotelo moves on to the next site.

The unit collects 110 ml of water every hour for 24 hours. 

Rushan Abayagunawardena, Vice President of IEI, says that the hourly process creates what’s called a composite sample, and that it’s more effective than grabbing a full sample at once. 

“Within these housing facilities, there could be any sort of variation that happens within that 24 hour period. So we want to capture that broad spectrum,” he said. 

Sotelo returns the next day to collect the samples and send them to CosmosID, a Rockville lab that does the testing for MDE.  

The testing is similar to the one used for nose swabs and can detect the amount of COVID in the wastewater sample. The results come back in about one to two days. 

“It's extremely accurate,” Dorsey said. “It cannot be used to determine exactly how many people are infected. It couldn't be traced, for instance, to an individual apartment.” 

Using wastewater to detect COVID-19 isn’t unique to Maryland. Other states like Utah and Colorado have been using the strategy as well.

Kellogg Schwab, a professor at the Johns Hopkins Bloomberg School of Public Health, has investigated viral outbreaks through wastewater for many years. He’s worked with the Centers for Disease Control and Prevention and state health laboratories across the country. 

“Wastewater epidemiology, as we call it sometimes, is a powerful tool that can be used,” Schwab said. “It is one of many parts to a more progressive public health assessment.” 

It doesn’t work for all viruses though - the flu, for example, doesn’t show up in fecal matter. 

Schwab and the health department's Greenbaum said that at first, it’s hard to tell whether there is an outbreak in a facility based on how much COVID there is in a single sample.

But eventually, the data will give bigger clues. 

“You can start to see trends and increases in the level of these particular micro-organisms in a waste stream,” Schwab said.

When levels of COVID increase over time in the wastewater samples, that may indicate an oncoming outbreak, and residents would receive notice. Greenbaum said if it’s a small increase, the health department would start with reinforcing safety guidelines like mask wearing and hand washing. 

If it’s a dramatic increase, Greenbaum said they would make more resources like nose swab tests available to a facility. 

“If we can test them, sooner than we would have tested them without that notification of COVID being in the wastewater, we hope they can isolate sooner, and then we can do contact tracing, and all of that can start earlier than if we would have waited for them to develop symptoms,” she said. 

Encouraging people to take the tests may be a challenge. Monica Watkins, the senior vice president of engineering, energy and capital improvements at HABC, leads the project in Baltimore. Watkins said part of her job is to build trust with residents. 

“We want them to be healthy. And we'll do what we can to help them also combat COVID in their neighborhood,” she said. 

Dorsey said spreading awareness around wastewater trends as well as recommending safety guidelines could be an effective strategy against outbreaks. 

“We couldn't force people to be tested,” she said. “The whole approach with this is not to be heavy handed, but to be collaborative with our local entities.” 

She described the project as a great learning experience for the Department of the Environment and its partners. 

“It’s really indicative of the pandemic bringing together cutting edge science, and really focusing it to save lives,” Dorsey said. “We've had a lot of conversations outside of Maryland. And everybody is just amazing at sharing lessons learned in their states: ‘hey, do this, don't do this. Try this.’”

HABC CEO Janet Abrahams sees the initiative as a stepping stone for future projects. 

“We have developed the relationship and the partnership with the health department and with the state,” Abrahams said. “From a partnership standpoint, to me, that was something that was lacking. And now I can see how well these partnerships work, especially for the good of our residents."

The pilot initiative, which began in mid-December, is set to run for six months. Watkins hopes that they can get more resources to continue the ongoing pilot initiative and use it for future epidemics. 

“The biggest thing is that we're pulling together,” Watkins said. “It's a group effort between us residents, the city, the state. And I think it's really commendable.”


Rachel Baye contributed reporting.

Sarah Y. Kim is WYPR’s health and housing reporter. Kim is WYPR's Report for America corps member, and Anthony Brandon Fellow. Kim joined WYPR as a 2020-2021 corps member for Report for America, an initiative of The GroundTruth Project that pairs young journalists with local newsrooms. Now in her second year as an RFA corps member, Kim is based in Baltimore City.