Two Omicron subvariants — BA.4 and BA.5 — are propelling the growth of COVID-19 infections this summer as they become the dominant coronavirus strains in the U.S.
These variants now make up 52.3% of infections, with BA.5 accounting for 36.6% of new cases and BA.4 accounting for 15.7% of new cases, according to the latest CDC data. The week before, the subvariants made up about 37.4% of cases.
Public health experts have expressed concerns about the subvariants because they’re more contagious and lead to higher numbers of reinfections, even among people who already contracted Omicron previously.
Their “superpower is reinfection,” Peter Chin-Hong, MD, an infectious disease specialist at the University of California at San Francisco, told the Los Angeles Times.
For instance, the subvariants are prompting a particularly high wave of reinfections in California. During the first Omicron wave between December through February, the state reported an average of about 14,325 reinfections per week, the newspaper reported.
That number dropped to about 2,315 weekly reinfections between March through May. Since then, weekly reinfections have grown alongside BA.4 and BA.5, reaching 10,409 in June.
In addition, overall COVID-19 cases have increased 26% in California in the last two weeks, reaching an average of more than 18,000 daily cases. Los Angeles County is reporting more than 5,000 cases per day, which is the highest case rate since early February.
“There’s strong evidence [BA.4 and BA.5] can spread even faster than other subvariants,” Barbara Ferrer, the Los Angeles County public health director, told the newspaper.
“There also have been some concerning findings in laboratory studies, which found that BA.4 and BA.5 were better able to infect lung cells than the earlier BA.2 subvariant of Omicron,” she said.
CDC data shows that BA.4 and BA.5 are affecting U.S. regions differently, with higher prominence in the South and Midwest than in the Northeast. Individual communities are also facing higher risks, depending on the overall level of immunity and the number of older residents and medically vulnerable people.
“All of the information to date points to the need for us to prepare for the likelihood of significant transmission in the upcoming weeks,” Ferrer said.
The U.S. is now reporting an average of about 113,000 cases per day, which has increased 13% in the last two weeks, according to the data tracker from The New York Times. The average has hovered around 100,000 cases throughout June, remaining stable but high nationwide. Cases are decreasing in the Northeast but rising in the South, even doubling or tripling in states such as Mississippi and Texas.
Hospitalizations have increased about 11% in the past two weeks, with about 34,000 COVID-19 patients hospitalized nationwide, according to the latest data from the U.S. Department of Health and Human Services.
About 387 deaths are being reported each day, the data tracker shows, marking a 24% increase in the past two weeks.
Although hospitalizations and deaths remain low compared to earlier Omicron waves, public health officials have warned about certain severe symptoms seen with the BA.4 and BA.5 subvariants, as well as the risk for ongoing health problems, particularly as people get reinfected again and again.
“In addition to symptoms that last for several months or more, there’s also a risk of other long-term complications that are set in motion by the original case of COVID-19,” Robert Wachter, MD, chair of the department of medicine at the University of California at San Francisco, wrote in a recent editorial for The Washington Post.
His wife, who first contracted COVID-19 earlier this year, was still dealing with symptoms such as extreme fatigue and brain fog seven weeks later, even though she was vaccinated and boosted.
“For reasons that aren’t completely understood, people who have had COVID have a significant increase in heart attacks, stroke, diabetes and blood clots, measured at least one year from the time of their infection,” he said. “These findings mean that, on top of the risk of chronic symptoms, a case of COVID may increase the long-term odds of several diseases that are among our leading causes of death and disability.”