BOSTON—At a sewage treatment plant on a sliver of land in Boston Harbor, trickles of wastewater are pumped into a plastic jug every 15 minutes. Samples from the jugs, analyzed at a lab in nearby Cambridge, Mass., are part of the growing effort to monitor the Covid-19 virus in wastewater across the U.S.
On Deer Island in Boston, readings from the system covering 2.4 million people have recently shown virus readings leveling off after a steep decline from this winter’s Omicron-driven rise. In some areas, levels of the virus may be edging higher.
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“The last few days have been a little worrisome,”
Larry Madoff,
medical director of the bureau of infectious disease and laboratory sciences at the Massachusetts Department of Public Health, said late last week. “It certainly bears careful watching.”
Wastewater sampling here and at hundreds of sites nationwide is once more drawing closer scrutiny from epidemiologists worried the spread of what appears to be a yet-more-contagious version of Omicron, known as BA.2, and rising cases in Europe could soon spoil the latest U.S. recovery. The number of wastewater sites indicating virus increases on a Centers for Disease Control and Prevention dashboard has risen in recent weeks, though the majority of sites still show declining levels.
In Boston and beyond, these systems during the Omicron wave helped quickly detect virus-concentration surges, declines and circulating variants, often before testing and case data. Health authorities believe it will become an increasingly important early-warning tool that can help guide public messaging and other responses, like marshaling resources to surging areas.
But the technique is also suffering some growing pains from a mix of technological, data-interpretation and logistical challenges as U.S. authorities try to build out a national system.
“We’re trying to figure out how you can take that data and turn it into public-health action and how that can be incorporated into a surveillance system,” said
Kelly Wroblewski,
director of infectious-disease programs at the Association of Public Health Laboratories. “It hasn’t quite matured yet.”
Researchers determined early in the pandemic they could track the new coronavirus through the sewers. The low-cost technique has speed and coverage benefits: People can shed virus in their waste before they feel sick enough to get tested. Many never get tests that generate results that can be tallied by public-health officials, especially now that people are self-testing more at home. States have also started closing testing sites and dialing back daily data reporting, making a passive data source like the…