Dr. Michael Sweat, medical director of the Maricopa County Department of Public Health, says he first noticed a possible trend in COVID-19 cases in early December 2021..
Sweat, who is based in Arizona, was looking at wastewater data from the county’s eight treatment plants, which can detect the presence of the virus that causes COVID-19. He saw a slight increase in the amount of virus in the wastewater, even though the number of reported cases was declining..
That increase in wastewater virus levels was a sign that the omicron variant was starting to take hold in Maricopa County, even though it had not yet been detected in any clinical samples..
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