Are covid-19 infections going back? There’s a potential caveat in sewer data

more than a third of the CDC waste water sample Sites across the US showed increasing COVID-19 trends in the period from March 1 to March 10, although reported cases have been low until recently. The number of sites with increasing signs of COVID-19 cases has almost doubled during the period from February 1 to February 10, when there was a wave of omicronVarious cases were fading fast.

It is not clear how many of the signs in sewage represent new infections and whether they will turn into a new wave, or just one brief collision On the way down from the last one. In many parts of the country, people are returning to offices and mask rules have been relaxed – factors that could increase transmission. At the same time, warmer weather is allowing people to spend more time outside, and many people who have recently been infected may offer at least temporary protection against getting sick again – factors that help reduce cases. Will keep

“While wastewater levels are generally very low across the board, we are seeing an increase in sites,” Amy Kirby, head of the CDC’s wastewater monitoring program, said in an email to Bloomberg. rises from very low level to still low level. Some communities, however, are beginning to see an increase in COVID-19 infections, as containment strategies have changed in several states in recent weeks. ,

Bloomberg reviewed data from more than 530 sewage monitoring sites, looking at the most recent data reported during the 10-day window from March 1 to March 10. Of those sites, 59% showed declining COVID-19 trends, 5% were largely stable, and 36% were rising. The rise or fall is measured over a 15-day period.

Fewer sites had data during the February 1 to February 10 window. During that period, 80% of the sites showed a decreasing trend, 5% were stable, and 15% were increasing.

Waste water samples cannot tell how many people have COVID-19. Instead, they measure how much virus is being found in sewer water. A higher concentration in a sample may indicate an increasing number of infections, often days before those cases show up in testing.

The official case numbers determined through COVID tests have become increasingly unreliable. With the wide reach of home tests, many infections – especially mild ones – are never reported. The proportion of unreported cases could be even higher in the midst of a surge and at a time when testing becomes difficult.

For example, over a large area of ​​New York City, there are signs of growth. While most area sampling sites do not have recent data, one wastewater site in Fairfield, Connecticut, appears to have a high rate of increase. A site in Nassau County shows a slight increase in the detection of COVID-19.

“It is too early to know whether this current trend will continue or whether we will see a similar increase in reported cases across the country,” the CDC’s Kirby said. “We encourage local health officials to monitor their numbers closely and use these data as an early warning sign if wastewater levels continue to rise.”

Signals are less than clear in some places. For example, in Miami-Dade County, one sampling site shows a decline in the amount of COVID found in wastewater. But two other sites for the county have increased. It is possible that the data is finding the start of a small, steady-local set of cases. Or the data may be based on a relatively low level of virus, which exaggerates the size of the change due to the low baseline.

People infected with the coronavirus shed viral particles in their feces, which are then flushed into the sewer system when using the toilet. Because they begin to release the virus early during infection, wastewater samples can quickly identify an increased trend of infection.

As of now, the warnings from the sewer network are not reflected in the number of cases and the number of patients being hospitalized for COVID-19 is still close to recent lows. The US population 65 years and older – among the most vulnerable to severe COVID-19, hospitalizations and deaths – is also the nation’s best immunization demographic. Eighty-nine percent of that group have been fully vaccinated, and 67% of those people have received a booster dose.

The increase in COVID wastewater warnings comes nearly two weeks after the CDC changed its recommendations in the country on masking and other public health measures. The agency revamped its recommendations to ensure that hospitals are not overwhelmed, and put much of the country at a “low” level of exposure to COVID.

According to the CDC’s latest Community Level Rating, 98% of the US population lives in places with a “low” community level rating. However, those ratings are based on case numbers and hospitalizations. Wastewater data can often show an increase in cases for several days before the number of cases rises.

Cases are rising in several European countries as the continent has gone through a similar pattern to the US’s Germany, Switzerland and Austria, as well as other European countries, all reporting a significant increase in the number of cases over the past two weeks. Given broad similarities in climate, population and public health attitudes, US trends often follow what happens in Europe.

This story has been published without modification in text from a wire agency feed. Only the title has been changed.