Covid Cases on the Rise in the U.S. A Strong Warning

According to a Bloomberg analysis of Centers for Disease Control and Prevention data, a wastewater network that monitors Covid-19 trends is warning that cases are once again on the rise in many parts of the United States.

More than a third of the CDC’s wastewater sample sites in the United States showed rising Covid-19 trends from March 1 to March 10, though reported cases remained near a recent low. The number of sites with rising signals of Covid-19 cases is nearly double what it was from February 1 to February 10, when the wave of omicron-variant cases was rapidly fading.

It’s unclear how many new infections the sewage signs represent, or whether they’ll be a new wave or just a brief blip on the way down from the last one. People are returning to work in many parts of the country, and mask regulations have been relaxed, both of which can increase transmission. Simultaneously, warmer weather allows people to spend more time outside, and many people have recently been infected, which may provide at least temporary protection against getting sick again – factors that would keep cases down.

“While wastewater levels are generally very low across the board, we are seeing an increase in sites reporting an increase,” Amy Kirby, the head of the CDC’s wastewater monitoring programme, told Bloomberg in an email. “These bumps could simply be minor increases from very low levels to even lower levels. However, as prevention strategies in many states have changed in recent weeks, some communities may be seeing an increase in Covid-19 infections.”

Bloomberg examined data from over 530 sewage monitoring sites, focusing on the most recent data reported during the 10-day period between March 1 and March 10. Out of those sites, 59% showed falling Covid-19 trends, 5% were roughly stable, and 36% were increasing. The rises and falls are calculated over a 15-day period.

During the period from February 1 to February 10, fewer sites had data. During that time, 80 percent of sites showed a decreasing trend, 5% remained stable, and 15% rose.

Wastewater samples cannot reveal how many people are infected with Covid-19. Instead, they count the amount of virus found in sewer water. A high concentration in a sample can indicate an increase in the number of infections, which can occur days before the cases are detected in tests.

Official case numbers derived from Covid tests have become increasingly untrustworthy. With more people having access to at-home tests, many infections, particularly mild ones, are going unreported. The proportion of unreported cases can be even higher in the midst of surges and when tests are scarce.

There are signs of an increase, for example, in the greater New York City area. While most sampling sites in the region do not have recent data, a wastewater site in Fairfield, Connecticut, shows a rapid increase. A moderate increase in Covid-19 detection has been observed at a site in Nassau County.

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

In some places, the signals are a little hazy. One sample site in Miami-Dade County, for example, shows a decrease in the amount of Covid found in wastewater. However, two other county sites show an increase. It’s possible that the data are uncovering the seeds of a small, still-local cluster of cases. Alternatively, the data could be based on a relatively low level of virus detected, exaggerating the magnitude of the change due to the low baseline.

People who are infected with the coronavirus excrete viral particles in their faeces, which then enter the sewer system when they use the toilet. Because they start releasing the virus early in the course of infection, wastewater samples can detect a rising trend of infections early on.

So far, the sewer network’s warning has not been reflected in case numbers, and the number of patients hospitalised for Covid-19 remains near recent lows. The 65-and-older population in the United States is the best-vaccinated demographic, despite being among the most vulnerable to severe Covid-19, hospitalisation, and death. Eighty-nine percent of that group has been fully vaccinated, and 67 percent have received a booster dose.

The increase in Covid wastewater warnings comes about two weeks after the Centers for Disease Control and Prevention (CDC) revised its recommendations to the country on masking and other public health measures. The agency revised its recommendations to focus on ensuring that hospitals were not overburdened, and classified much of the country as “low” in terms of Covid risk.

According to the most recent CDC community level rating, 98 percent of the population in the United States lives in areas with a “low” community level rating. However, those ratings are based on case numbers and hospitalizations. Wastewater data can often detect an increase in cases several days before the number of cases increases.