A wastewater network that monitors Covid-19 trends warns that cases are growing again in many parts of the U.S., according to data from Bloomberg’s Centers for Disease Control and Prevention.
More than a third of the U.S. CDC’s wastewater sampling sites were prone to the Covid-19 trend, which ran from March 1 to March 10, although reported cases have been reported since the last minute. The number of sites with a rising signal of Covid-19 cases is almost double what it was between February 1 and February 10, when the wave of omicron variant cases was rapidly disappearing.
It is unclear how many new water signs indicate infection and will turn into a new wave, or whether it will be a brief blow on the way down from the last one. In many parts of the country, people are returning to their offices and the rules of the mask have been released – factors that could increase transmission. At the same time, the warmer weather is allowing people to spend more time outside, and many people have recently been infected, which could provide temporary protection from getting sick again – factors that could bring cases down.
“While wastewater levels are generally very low, we are seeing an increase in sites that are on the rise,” Amy Kirby, head of the CDC’s wastewater monitoring program, said in an email to Bloomberg. “These balks may reflect small increases from very low to low levels. Some communities, however, may begin to see an increase in Covid-19 infections as prevention strategies have changed in many states in recent weeks.”
Bloomberg reviewed data from more than 530 sewage monitoring sites, focusing on the latest data reported in its 10-day window from March 1 to March 10. Of these sites, 59% had Covid-19 trends down, while approximately 5% were stable. , and were increasing by 36%. Ascents or descents are measured within 15 days.
Fewer sites had data from Feb. 1 to Feb. 10. During this period, 80% of the sites were on a downward trend, 5% stable and 15% up.
Wastewater samples cannot tell how many people have Covid-19. Instead, they measure how much virus is found in sewer water. A high concentration in a sample may indicate an increasing number of infections, often a few days before these cases appear in the tests.
Official numbers of cases determined by Covid trials are becoming increasingly reliable. With wider access to home testing, many infections – especially mild ones – have never been reported. The proportion of unreported cases may be even higher in the midst of the rise and at times when testing has been difficult.
In the greater New York City area, for example, there are signs of a rise. Although most of the sampling sites in the region do not have the latest data, one of the Fairfield (Connecticut) wastewater sites shows a significant increase. A site in Nassau County shows a moderate increase in Covid-19 detection.
“It is too early to know whether this current trend will continue or whether we will see an increase in reported cases across the country,” CDC’s Kirby said. “We encourage local health officials to monitor their numbers closely and use this data as an early warning if wastewater levels continue to rise.”
In some places, the signs are less than clear. In Miami-Dade County, for example, a sample site shows a decrease in the number of Covids found in wastewater. But the other two sites in the region are on the rise. The data may still find the beginnings of a small set of local cases. Or the data could be based on a relatively low level of viruses found, increasing the size of the change due to the low baseline.
People infected with coronavirus discharge viral particles into their stools and then discharge them into the sewer when they use the toilet. As the virus begins to spread at the beginning of the infection, wastewater samples can identify an early upward trend in infections.
To date, the warning given by sewer networks has not appeared in a number of cases and the number of patients hospitalized for Covid-19 is still close to the last minimum. The 65-year-old U.S. population — one of the most vulnerable to severe, hospitalized, and lethal death in Covid-19 — is also the demographic of the best vaccine in the country. 89 per cent of this group are fully vaccinated, and 67% of these people have received a booster dose.
The increase in Covid wastewater warnings comes about two weeks after the CDC changed its recommendations on masking and other public health measures. The agency renewed its recommendations to some extent to ensure that hospitals are not overcrowded and put much of the country at a “low” level of risk for Covid.
According to the latest CDC community-level assessments, 98% of the U.S. population is in places with a “low” community-level assessment. These assessments, however, are based on case numbers and hospitalizations. Wastewater data can often rise in the case a few days before the number of cases rises.
Cases are on the rise in several European countries as the continent has followed a similar pattern to the US. Germany, Switzerland and Austria, as well as other European countries, have seen a significant increase in the number of cases in the last two weeks. US trends often follow what is happening in Europe, given the sharp similarities between the climate, the population and the public health outlook.
(Except for the title, this story has not been edited by NDTV staff and has been published from a union feed.)