“It’s too early to know if this current trend will continue or whether we’ll see a corresponding increase in reported cases across the country,” said the CDC’s Kirby. “We encourage local health officials to monitor their numbers closely and use these data as an early warning sign if wastewater levels continue to increase.”
In some places, the signals are less than clear. In Miami-Dade County, for example, one sample site shows a decline in the amount of Covid found in wastewater. But two other sites for the county show an increase. It’s possible the data are finding the beginnings of a small, still-local cluster of cases. Or the data could be based on a relatively low level of virus found, exaggerating the size of the change because of the low baseline.
People infected with the coronavirus shed viral particles in their stool, which then flows into the sewer system when they use the toilet. Because they begin to give off the virus early in the course of infection, wastewater samples can identify a rising trend of infections early on.
So far, the warning given by the sewer networks hasn’t shown up in case numbers and the number of patients being hospitalized for Covid-19 is still near recent lows. The 65-years-and-older population in the U.S. — among the most vulnerable to severe Covid-19, hospitalization and death — is also the country’s best-vaccinated demographic. Eighty nine percent of that group is fully vaccinated, and 67% of those people have received a booster dose.
The increase in Covid wastewater warnings comes about two weeks after the CDC changed its recommendations to the country on masking and other public health measures. The agency revamped its recommendations to focus in part on making sure hospitals were not overwhelmed, and put much of the country in its “low” level of Covid risk.
According to the CDC’s latest community levels rating, 98% of the U.S. population is in places with a “low” community level rating. Those ratings, however, are based on case numbers and hospitalizations. Wastewater data can often pick up a rise in cases several days before case numbers rise.
Cases are on the rise in several European countries after the continent went through a similar pattern to the U.S. Germany, Switzerland and Austria, as well as other European countries, have all reported significant increases in case numbers over the last two weeks. U.S. trends often follow what happens in Europe, given the rough similarities in the climate, population and public health approach.
This article was provided by Bloomberg News.