COVID-19 cases in Hamilton County are at their highest levels since the initial omicron surge in early 2022 as new, more contagious versions of the omicron variant drive the latest wave of infections.
The Chattanooga region's latest wave comes amid a national COVID-19 surge that has been gaining steam since mid-April as a result of omicron subvariants BA.4 and now BA.5, which according to tracking from the U.S. Centers for Disease Control and Prevention became the dominant coronavirus variant in both the Southeast and the United States as a whole in early July.
Both subvariants are better than any prior strain at evading immunity from previous infection and vaccination, and they're the most contagious versions of the coronavirus yet.
"Each new variant that comes out is more contagious, and biologically, that makes sense," Dr. Mark Anderson, an infectious disease specialist at CHI Memorial Hospital, said in a phone interview.
Unlike earlier versions of the coronavirus, the omicron subvariants appear to be less deadly as a whole but far better at evading antibodies.
Eric Topol, a professor of molecular medicine at Scripps Research, said in a recent New York Times article that prior infection with another form of the omicron variant does offer some degree of immunity.
"But it's not anything like what we would hope," Topol said.
Despite most infected people nowadays either using at-home tests or not testing at all, the current surge represents the fourth largest in terms of the number of confirmed COVID-19 cases reported to the Hamilton County Health Department over the course of the pandemic.
As of Monday, the county was averaging 149 new cases per day over the past week, according to Health Department data.
By comparison, during the peak of the first omicron surge, the county posted a seven-day average for new daily cases of 898 in a week. The next largest surge occurred in January 2021, when the county averaged 514 new daily cases in a week, followed by a seven-day average of 342 new cases in September 2021.
Still, since the initial omicron surge infected so many people, it may explain why the current wave is more of a steady rise as opposed to a dramatic spike in new infections.
In addition to omicron variants seeming to cause less serious illness as a whole, Anderson said immunity from vaccination or prior infection is likely also helping to keep hospitalizations low.
There were 47 COVID-19 patients in Hamilton County hospitals as of Monday, but that's nowhere near as high as previous surges. As of Friday, eight of those patients were in intensive care, according to the Health Department.
"At this point, there aren't very many people that have not either been vaccinated or had COVID, or both, so there's just more general immunity in the population," Anderson said.
Anderson said many of those hospitalizations are what's called "incidental infections," meaning people came to the hospital for a reason not related to COVID-19 and then wound up testing positive.
The CDC warns that anyone infected by omicron, including those who are vaccinated or without symptoms, can spread the coronavirus to others, though vaccination continues to help people experience milder symptoms and avoid the worst effects of the virus.
Anderson said older adults and people with compromised immune systems continue to be most at-risk and should take precautions.
"Those are the ones who have to be especially careful and avoid being in crowded, enclosed spaces with the people they don't know or in crowds among people who aren't wearing masks," he said. "That group, in particular, are the ones I worry most about, who need to be warned."