The city of Burlington reported record high Covid-19 concentrations at two of its three wastewater treatment plants late last week, according to the city’s website.
The data collected on Jan. 17 shows skyrocketing Covid levels at the East Plant and North Plant in Burlington. The Main Plant’s levels remained relatively flat compared to the previous week.
The three plants in Burlington are among more than a dozen facilities in Vermont that test samples of wastewater for concentrations of the Covid virus. Wastewater testing can be an “early population-based signal that COVID levels are rising or declining,” Vermont Department of Health spokesperson Katie Warchut said in an email.
However, she cautioned that “wastewater levels can vary from week to week.” Burlington’s own data bears that out: On Dec. 27, the East Plant reported one of its highest concentrations of Covid, only to drop to its lowest point in months by Jan. 9.
Warchut said sharp increases from week to week are one indicator the department uses to become more confident that an uptick is a “true rise.”
But another indicator — that all sites are increasing simultaneously — does not apply here, she said. The Main Plant in Burlington remained flat, and other wastewater testing sites in the region have not reported an uptick, according to data from the U.S. Centers for Disease Control and Prevention.
CDC data on wastewater testing has been inconsistently reported and does not identify the precise location of sites, making it hard to compare with state data. The latest CDC report indicates an uptick at some testing sites, but not as dramatic an increase as Burlington reported. Winooski and South Burlington reported a decline in wastewater concentrations in the past week, Warchut said.
The last condition that the health department considers to indicate a rise in Covid levels is whether the concentrations recorded at these sites increase week after week. Updated data from the plants in Burlington should be available later this week, according to Meagan Tuttle, the city’s planning director.
The latest surveillance report from the state health department reported low Covid community levels statewide, based on hospitalizations and Covid case data. But that report was based on data for the week of Jan. 8 to Jan. 14, meaning Burlington’s wastewater results are more recent.
“So far we have not seen evidence of disease increase in our other indicators,” Warchut said. “Since wastewater is an early indicator, we will carefully monitor indicators over the next week.”