The municipalities of Greenfield, Deerfield, Sunderland and Montague are experiencing the largest COVID-19 outbreak the region has seen since January, according to epidemiologist Jack Sullivan.

Increased COVID-19 detection in wastewater samples, corresponding with an elevated number of COVID-19 cases across the four municipalities, is bringing the region into the red zone, with a high risk of COVID-19 transmission. The four municipalities are among the local communities to participate in a testing program to track the concentration of COVID-19 in the wastewater system, as people with an active infection excrete the virus in their stool.

While weighted averages collected by the collaborative reflect a roughly 10% increase in COVID-19 cases across the communities, Sullivan reported that an average of 1.3 million copies of COVID-19 per liter of wastewater were detected. He explained more than 1 million copies puts a city or town in the “level red” category.

“The thing to remember about wastewater is that, unlike tests, wastewater is also giving us an indication that there are asymptomatic people out there, people who are infected but aren’t showing any symptoms. That doesn’t mean they’re not infectious, and doesn’t mean that they can’t transmit the disease. It’s just that they’re not suffering from the symptoms of COVID-19, but nonetheless, they are expelling it into the wastewater,” Sullivan said. “Right now [wastewater testing] is our best indicator for what’s circulating, because the number of lab-reported tests are really just a fraction of the number of cases that are out there, since most people are doing at-home tests now.”

With the exception of Sunderland, where wastewater COVID levels trended at approximately 775,900 copies per liter, all communities saw more than 1 million copies of COVID-19 per liter in their wastewater — Deerfield with 4.74 million copies per liter, Greenfield with 1.1 million copies per liter and Montague with 1.64 million copies per liter.

Sullivan said that while the virus typically peaks in the winter, with slight upticks common in the summer and fall when large gathering are more common, students return to school and new strains of the virus tend to appear. Citing information from the Centers for Disease Control, he said the latest COVID-19 strain KP.3.1.1 comprises roughly 42% of current cases.

“One of the things that’s happened with Omicron and with some of the subvariants that have been growing off of that is that there is more of a chance of the virus residing in the gut, where before it was in the respiratory system,” he said. “It still does reside in the respiratory system, but it also replicates in the gut, so that you’re seeing more GI-related symptoms. One of the things about it being in the gut is that when people expel it, that’s a higher concentration level that we’re seeing in the wastewater.”

Greenfield Communications Director Matthew Conway said although the city will not take any immediate action to mitigate the spike, the Health Department will distribute masks and at-home COVID-19 test kits to those who need them. Sullivan added that some “commonsense” measures, such as ensuring crowded gathering spaces have adequate ventilation, wearing masks and  getting the latest version of the vaccine, are all effective strategies to avoid spreading the virus.

“You want people to live their lives and you can do that with some commonsense mitigation efforts,” Sullivan said. “It’s not a mandate to wear a mask, but especially if you’re feeling symptoms or if you have vulnerable people in your family, elderly people or somebody who’s immunocompromised or at risk with other comorbidities like diabetes or respiratory issues, it only makes sense to protect yourself and them by wearing one.”