As many Americans drive home for Christmas, COVID-19 levels are high or very high in 20 U.S. states, according to recent wastewater analysis by the U.S. Centers for Disease Control and Prevention (CDC).
Since the beginning of the pandemic, the CDC has tracked levels of SARS-CoV-2—the virus that causes COVID-19—in wastewater, including sewage.
This data captures infection levels from everyone using the wastewater system, including those without symptoms, who haven't tested for COVID-19 and who haven't reported their illness.
Wastewater testing can therefore give an earlier and more accurate indication of COVID-19 levels as the infection spreads to different areas, rather than just relying on positive tests.
The most recent wastewater data, published by the CDC on December 19, estimates levels of COVID-19 from Saturday, December 8 to Sunday, December 14.
It shows that five states reported "very high" levels of SARS-CoV-2, compared to six the previous week and just two the week before.
This time, these states were Kansas, Missouri, New Hampshire, New Mexico and South Dakota—although Missouri and South Dakota's results were based on limited data.
This means data from these states were based on less than 5 percent of the population so might not be representative of residents throughout each state.
A total of 15 states and the District of Columbia reported "high" levels of the virus—three more than the week before—including Arkansas, Illinois, Indiana, Iowa, Kentucky, Maine, Massachusetts, Minnesota, Nebraska, Ohio, Rhode Island, South Carolina and Wyoming, as well as Arizona and Pennsylvania which were based on limited data.
Meanwhile, Alabama, Colorado, Connecticut Delaware, Idaho, Maryland, Montana, Oklahoma, Utah and Wisconsin were the 10 states with "moderate" levels of the virus.
Only 12 states had "low" levels and six had "minimal" levels, including Mississippi which used limited data.
"Wastewater [sewage] can be tested to detect traces of infectious disease circulating in a community, even if people don't have symptoms," says the CDC's website. "You can use these data as an early warning that levels of infections may be increasing or decreasing in your community."
Wastewater analysis can also reveal the COVID-19 variants which are circulating more than others, again based on data from the week ending December 14.
Currently, KP.3 and KP.3.1.1 strains are on the decline, at 16 and 26 percent respectively, while XEC seems to have become more prevalent at 29 percent.
An older strain called JN.1 seems to be at 7 percent and MC.1, which was at 6 percent the week before, has ducked below the 5 percent threshold of reporting. Miscellaneous "other" variants, presumably including MC.1, now make up 21 percent of the disease.
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