Even during the Christmas festivities, COVID-19 was infecting people around the country, sending wastewater levels soaring.
New data from the U.S. Centers for Disease Control and Prevention (CDC) revealed which U.S. states had "very high" levels of SARS-CoV-2—the virus that causes COVID-19—present in wastewater between December 22 and December 28.
The CDC tests wastewater for viruses like COVID-19 as part of a public health strategy called wastewater surveillance, which allows officials to detect the presence and trends of infectious diseases in a community.
In total, 16 states had "very high" levels of the virus during this period, which is an increase from 14 states with "very high" levels the week before.
The states with "very high" levels included: Illinois, Indiana, Iowa, Kansas, Maine, Michigan, Minnesota, Nebraska, New Hampshire, New Mexico, Pennsylvania, Rhode Island, South Dakota, Virginia, Wisconsin and Wyoming.
Only two weeks prior, between December 8 and December 14, only five states had "very high" levels of the virus present.
Between December 22 and December 28, Alabama, Arkansas, Colorado, Connecticut, Delaware, Georgia, Louisiana, Maryland, Massachusetts, Ohio, Utah and Vermont had "high" levels of wastewater COVID-19, while Idaho, Oklahoma, South Carolina and Tennessee had "moderate" levels.
Meanwhile, Alaska, California, Florida, Mississippi, Montana, Nevada, New Jersey, North Carolina, Texas and Washington had "low" levels, and Hawaii and New York had "minimal" levels.
Arizona, Kentucky, Missouri, North Dakota, Oregon, West Virginia and D.C. have no data available for this period.
Additionally, Illinois, Michigan, Mississippi, North Carolina, South Carolina, South Dakota, Tennessee and Virginia have "limited coverage" for this week's data, meaning that their recorded viral activity is "based on a small part (less than 5 percent) of the population and may not represent viral activity levels for the entire state or territory," the CDC explains.
Testing wastewater can reveal the presence of a virus in a community before people start showing symptoms or getting tested individually, as viral particles from infected people can be excreted in urine or feces, even if they are asymptomatic.
"Wastewater monitoring can detect viruses spreading from one person to another within a community earlier than clinical testing and before people who are sick go to their doctor or hospital. It can also detect infections without symptoms," the CDC explains.
"If you see increased wastewater viral activity levels, it might indicate that there is a higher risk of infection."
This method is a non-invasive way to gather population-level health data without requiring direct interaction with individuals, and is relatively inexpensive compared to widespread individual testing.
Testing data for the same period reveals that 7.1 percent of COVID-19 tests came back positive across the U.S., with the highest test positivity rates in the Northwestern states.
"Many respiratory virus illnesses peak during the winter due to environmental conditions and human behaviors," a CDC spokesperson previously told Newsweek.
"COVID-19 has peaks in the winter and at other times of the year, including the summer, driven by new variants and decreasing immunity from previous infections and vaccinations."
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