Over the next week, most of Cortland County will likely see few if any new coronavirus cases.
This is not a psychic prediction, but what is suggested by the results of a new test that detects coronavirus RNA in wastewater. However, officials caution against drawing hasty conclusions from the results until more testing is done.
Last week, the city’s wastewater treatment plant began submitting samples for the test, which is part of a program run by Syracuse University public health researchers. Monday, county and city officials received the first test results.
Those results are encouraging, said Bruce Adams, the city’s director of wastewater. But the precise meaning of the first test results is still unclear. Adams said the results could mean there are no new cases, or just the number of new cases is below the test’s detection limit.
David Larsen, the environmental epidemiologist who runs the testing program, said more samples need to be taken — partly to help researchers figure out how sensitive their test is, and how much dilution caused by precipitation affects results.
“We don’t yet know the limit of detection of this method,” Larsen said.
Based on the already available county coronavirus infection data, he expected the county’s numbers to be fairly low — possibly low enough that the test reads them as a null result, or zero.
“I would suspect it is low transmission given the case data that I’ve seen,” he said. “That does not mean there is no transmission in Cortland.”
By mid-June or July, researchers will have a better sense of the test’s detection limit, Larsen said.
“Right now they’re determining how sensitive it (the test) is,” said Mike Ryan, the county’s environmental health director. “It’s research more than it is a reporting system at this time.
We’re excited about it. … Right now it doesn’t give us too much more information than we have already.”
The test “gives a picture … of a rough percentage of infected persons in the collection area,” Adams said.
The collection area for the test is the same as that covered by the city’s wastewater treatment system — the city’s residents in addition to those of the village of Homer, the village of McGraw and much of the town of Cortlandville, or between 55 and 65 percent of the county’s residents, Adams estimated.
While the test can detect people who were or currently are infected with the virus, most of the cases it picks up are of people who have recently been infected and not yet begun to show symptoms, as well as the asymptomatic, he said.
The test essentially provides a glimpse of infections a week ahead of time, Larsen said.
Adams submitted another sample to the program Tuesday, and will continue to submit samples weekly. Larsen said he hopes to test twice weekly in the near future.
Cayuga, Onondaga, Tompkins, Oswego, Warren, Saratoga and Westchester counties are participating in the program, and Larsen has requested that the state Health Department expand the program statewide.