BOSTON, Mass. — Stool holds a vital role in a very useful public health tool called water-based epidemiology.
"I think it can be useful to give an early signal that there's increased disease activity, either in a community or even in a building, depending on what level you're sampling the wastewater at," said Dr. David Hamer, an infectious disease physician at Boston Medical Center and a professor of global health and medicine.
Hamer says wastewater can detect the prevalence of SARS-CoV-2, the virus that causes COVID-19.
"The (Centers for Disease Control and Prevention) is now trying to have more of a national level coordination of wastewater surveillance, which is fantastic," Hamer said. "But in Boston, there's a group that began doing it at Deer Island, which is a wastewater treatment facility for the Greater Boston area."
The Massachusetts Water Resource Authority is a water treatment facility on Deer Island. That's where the feces of 2.3 million people are analyzed multiple times every week. The company behind the technology is Biobot Analytics.
"Biobot has partners in 25 states and around 200 facilities at the moment," said Kyle McElroy, a principal research scientist at Biobot.
McElroy says the RNA of SARS-CoV-2 is shed in stool. Since everyone goes to the bathroom, he says wastewater provides an accurate look at how many people in an area are infected with the virus.
"Wastewater gives you a look at the state of the pandemic that is not dependent on people's access to testing," McElroy said.
Right now, wastewater analysis shows COVID-19 cases are up across the country. Boston is facing a huge spike.
"Back in December and January of last year we had a fairly large wave with fairly high levels," Hamer said. "In the recent spike, we've reached levels that are that high, almost higher on average, and that really is quite worrisome, suggesting that there is a lot of virus in the community."
It's puzzling, considering the greater Boston area has some of the highest vaccination rates in the country.
However, the CDC currently defines a person as "fully vaccinated" after they receive two doses of the Pfizer or Moderna vaccines or one dose of the Johnson & Johnson vaccine.
According to Natalie Exum, assistant scientist at Johns Hopkins Bloomberg School of Public Health, a booster shot is necessary for the strongest protection possible against COVID-19.
"I hesitate to even call it breakthrough infections, because it assumes that something has gone wrong," Exum said. "This is actually exactly what you would expect with waning immunity for the vaccinated with two doses. I think we're going to move to a world where we say fully vaccinated is three doses. You're seeing more infections within that population, and in addition, that population also has their guard down."
Exum says not enough people have gotten the vaccine for it to be fully effective in preventing the spread of disease, and the delta variant is highly transmissible. Hamer adds that recent data from Africa shows the omicron variant will be even more transmissible.
Researchers say the good news is that vaccination will likely prevent a person from severe disease, hospitalization or death.
"If you do have the vaccine, you may inhale so much of the virus that you actually do get infected," Exum said. "And so, in that case, you will become symptomatic, you will be in your bed for a day for a day or two, but you're not going to go to the hospital, you're not going to require oxygen. And more importantly, you're probably at a lesser risk of getting long COVID."
Monitoring wastewater can help communities know when they need to have more control measures, like indoor mask mandates or more rapid testing.
"Say you started doing daily — or a couple of times a week — sampling the wastewater from a nursing home," Hamer said. "You might be able to detect when they're just starting to have an outbreak and then go in and more aggressively vaccinate, or, if you have treatments available — and do things to try and crush the outbreak."