Following an increase in the concentration of COVID-19 gene copies – fragments of virus found in the feces of infected or newly infected humans – levels have dropped in local wastewater over the past week.
The rise was first highlighted by Altamonte Springs City Manager Frank Martz after a reading on Thursday, April 7 in the Altamonte Springs sewer service area showed a 1,661% increase in COVID-19 concentration since March 10. The Casselberry sewer service area saw an increase of 4,323% over the same period.
Since then, COVID-19 virus concentrations have dropped from 488,307 copies per liter on April 7 to 180,399 copies per liter from Monday in the Altamonte sewer area and from 226,558 copies per liter on April 7 to 26,368 Monday in the Casselberry sewer area.
This drop over nearly two weeks suggests that there is not that much COVID-19 viral load in society now, said Edwin Oh, an associate professor at the University of Nevada, Las Vegas Kerkorian School of Medicine. Oh leads a wastewater monitoring program in collaboration with researchers from neighboring states.
“What we’re looking for when we look at these wastewater treatment plants is a trend, a week-to-week type trend,” Oh said.
Viral load by itself cannot convey the number of people in a community with COVID-19. Two people who test positive may each have different amounts of the virus in their bodies, which is one of the reasons why trends like declines and increases instead of copies per liters are important.
“Ultimately, wastewater is a great complement to other public health tools that we use to find out infection levels in a community,” Oh said.
There are other signals that Florida could see a slight increase in COVID-19 cases.
Hospital admissions, which the Centers for Disease Control and Prevention has increasingly emphasized as a measure of whether to be concerned about COVID-19, have increased by 1% in Florida, according to data collected by the Department of Health and Human Services New York Times, even if they are at low levels. In Orange County, there were 57 COVID-19 hospital admissions from 12-18. April, a 32% change from the week before, according to HHS.
Orange County’s positivity rate has been rising over the past few weeks, up 6.7% Thursday, the Orange County Department of Health announced on Twitter.
With the rise in home tests, many cases can remain unreported, making it harder to get a representative picture of society based on positivity rates, said Thomas Hladish, a University of Florida researcher who helped create a model that predicted the rise and fall of the omicron rise. There may be far more positive cases than the government is aware of, he said on Tuesday.
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“It doesn’t matter if I wanted the states to know I was tested positive. I have no way of getting it to count,” Hladish said.
The big question is whether any of these small increases in cases and hospitalizations could be the beginning of a BA.2-driven increase in Florida or across the United States. Hladish does not believe that the state is at the beginning of yet another major increase, although he believes that in the end there will be another increase.
BA.2 has been the dominant COVID-19 variant in central Florida wastewater for weeks, and there still appear to be only modest increases in cases and hospitalizations, he said. Many people caught COVID-19 during the winter omicron wave, giving them temporary immunity.
“If it were to pick up speed, I think we should already see it,” Hladish concluded.
Elena Cyrus, an epidemiologist at the University of Central Florida, is not so sure. The small increase in cases may be a result of the crowds during the spring break, she noted – but it may be something more.
“It’s likely we do not want another significant increase, but I think we will have to wait for the data within the next two to three weeks to confirm the direction,” she said.