NEW HAVEN — Fecal samples collected from a local sewage plant, which are tested as an early indicator of an uptick in COVID-19 infections, are showing a considerable uptick in the concentration of the novel coronavirus, according to data.

Scientists with Yale University found that the concentration of COVID-19 RNA in stool samples correlated with hospitalization rates roughly three days later.

“Cases are increasing in New Haven and there’s multiple lines of evidence to show that. We’re not the only ones saying that cases are increasing,” said Jordan Peccia, professor of environmental engineering at the Yale School of Engineering and Applied Sciences and a leader of the fecal testing project.

The data published by COVIDTrackerCT shows the number of copies per mL of sludge has risen from no higher than 10,000 with three daily exceptions between June 30 and Sept. 30 to samples exceeding 20,000 copies per mL of sludge four times in October. On samples tested on Oct. 26, the tracker reported more than 50,000 copies per mL of sludge, a sharp increase from all other days of data.

Peccia said the actual numbers are less important in data collection and reporting than the general trend, which he said is unmistakable.

“Things are trending up,” he said.

He said that as a general rule of thumb, 1,000 to 2,000 copies of coronavirus RNA in a sample would equal one new daily case. He said that because of the speed with which his team is able to collect and report data, the sewage data often leads the rest of the state by about three to five days in reporting new cases.

The waste tested from the East Shore Water Pollution Abatement Facility would include samples from municipalities within the region but outside New Haven city limits, such as East Haven, Woodbridge and Hamden.

“We have been following the wastewater numbers and other COVID indicators closely and are very concerned about the uptick,” said New Haven Mayor Justin Elicker. “We have been having meetings this week and anticipate some actions later this week in response to the increase in cases in the region.”

Elicker declined to specify what actions the city was considering.

City Health Director Maritza Bond said that if the numbers continue to increase she “will have to make tough decisions on making recommendations.”

“I’m trying to avoid that,” she said. “We cannot do this individually. We have to do it collectively.”

Bond said the city’s guidance around reducing transmission is mask wearing, social distancing and regular hand washing.

Mark Abraham, executive director of the local nonprofit DataHaven, monitors COVID-19 data. He said the latest development with sewage “looks bad.”

“On Friday of last week, I noticed a substantial uptick in the levels of the virus that causes COVID-19 in the public data report on New Haven area wastewater, which is one of the data sources that we look at each day,” he said. “The report suggests that they have climbed to much higher levels since then. It can take a few days to establish a clear trend, but the degree of increase this week, which has also been seen in Boston, is certainly concerning.”

City officials announced this week, prior to the significant uptick, that infections were increasing in the city. As of Monday, the city reported 3,438 documented cases of the virus, an increase of more than 200 cases within the last two weeks. City Health Director Maritza Bond said the city was also waiting on reporting data from two laboratories, so the city may have been underreporting the number of cases.

Elicker said contact tracing efforts found that much of the transmission was coming from small social gatherings of family and friends where people were not as cautious about protocols such as mask wearing and meeting outside.

On Tuesday, Gov. Ned Lamont reported the state had an average rate of 16.5 new cases per 100,000 residents per day over a seven-day span. New Haven’s average rate is lower than that, with Bond reporting it to be between five and nine new cases daily per 100,000 people.

brian.zahn@hearstmediact.com