BQ.1 and BQ.1.1 subvariants together drove an estimated 11.4% of recent U.S. cases New offshoots of the Omicron Covid-19 variant that virus experts say appear to spread easily are on the rise in the U.S., the latest federal data show, underscoring how the virus is mutating and presenting new risks as it proliferates.
Two of the Omicron subvariants, both related to the BA.5 version that drove the most recent U.S. surge, are called BQ.1 and BQ.1.1. They were estimated to represent a combined 11.4% of U.S. Covid-19 cases by mid-October, according to estimates the Centers for Disease Control and Prevention released Friday.
BA.5 remains the dominant version of the virus circulating in the U.S. at about 68% of recent cases, according to CDC estimates. But the subvariant landscape has become busier as the virus that causes Covid-19 continues to mutate. Another version virus experts are watching because of its potential to spread easily, called BA.2.72.2, represented an estimated 1.4% of cases in the latest CDC report.
“There’s just a swarm of them,” said Marc Johnson, a professor of molecular microbiology and immunology at the University of Missouri School of Medicine. “They all want to be the next big thing.”
Recent changes in the mix of variants in the U.S. don’t appear to have significantly affected the pandemic’s trajectory in the U.S. It can take time before a subvariant is prominent enough to have such an impact.
Viruses including the one that causes Covid-19 change randomly as they transmit and replicate. Many mutations have a negligible effect or can be detrimental to the virus. But some mutations give the virus advantages to help it spread.
Many subvariants researchers are watching closely have separately picked up some of the same advantageous mutations, Dr. Johnson and other virus experts said, a process called convergent evolution. Many of these mutations appear to help the virus get around our current immune defenses to some degree, they said.
One study that hasn’t been peer reviewed suggests that BQ.1.1. and other new subvariants might be more resistant to some current antibody treatments. Antivirals should remain effective, said Shishi Luo, head of infectious diseases at Helix OpCo LLC, a population genomics company involved with Covid-19 testing and sequencing.
The BQ subvariants’ quick rise “suggests that they either have increased transmissibility or increased immune escape compared with BA.5.,” said Dan Barouch, who directs the Center for Virology and Vaccine Research at Boston’s Beth Israel Deaconess Medical Center.
It isn’t clear that the BQ subvariants will take over in the U.S. or elsewhere, said T. Ryan Gregory, a professor in the Department of Integrative Biology at the University of Guelph in Canada. It is possible that multiple variants end up displacing BA.5 without becoming individually dominant, he said.
Nationally, key metrics such as hospitalizations have largely been on a downward trajectory since late July, following a BA.5-fueled summertime surge, but with some recent signs of wavering. Wastewater virus readings have been choppy in recent weeks due to a climb in the Northeast, according to data from Biobot Analytics. The Northeast has also seen a recent rise in new Covid-19 hospital admissions, federal data show.
Cases, which have become difficult to track due to at-home testing that health departments don’t monitor, were recently slightly below an average of 40,000 new cases a day, CDC data show. The average reached around 130,000 during the BA.5 surge in July, though epidemiologists caution the true number of cases is likely many times higher than records show.
The country has recently averaged about 330 newly reported Covid-19 deaths each day, a continued burden falling heavily on the elderly and people with underlying health issues, including compromised immune systems.
Case and hospitalization numbers are on the rise again in parts of Europe, but this appears to be caused principally by the BA.5 subvariant, said Trevor Bedford, a computational biologist at the Fred Hutchinson Cancer Center.
The interplay of a changing virus and fading immune protection from earlier infections and vaccine shots has left people vulnerable to repeated cases. These can lead in some cases to long-running symptoms. But virus experts say built-up protections from vaccines and prior infections still matter and can help limit hospitalizations and deaths.
Virus experts said that, because the newer subvariants remain in the Omicron family, updated Covid-19 vaccines in the U.S. should be an important shield against severe illness and death, though data is limited. The bivalent shots were designed to fight the original virus strain as well as the BA.4 and BA.5 Omicron subvariants.
“I think we can go in with the assumption that it bodes well for the bivalent booster,” said Helix’s Dr. Luo.
Data released by Pfizer Inc. and BioNTech from adults ages 18 and up found that the new Covid-19 booster generated a strong immune response against BA.4 and BA.5, the companies said.
About 14.8 million people in the U.S. have gotten the updated booster shot so far, CDC data show.
“October should be the month where we are getting that bivalent vaccine and getting our flu shot,” said Dr. Jodie Guest, a senior vice chair in the epidemiology department at Emory University’s Rollins School of Public Health.