Wily Covid-19 variant sweeps US, dodging immune defenses

UNITED STATES President Joe Biden joins a rising national Covid-19 wave dominated by a fast-spreading new variant known as BA.5, a wily evader of immune defenses.

Infections have been on the rise in the US, with 177,000 new cases reported on July 19, up from roughly 27,000 new cases on April 1. Los Angeles is seeing so many positive cases that it’s likely to bring back indoor mask mandates next week, and San Francisco virus levels in wastewater have climbed higher than this winter. The hospitalization rate has been inching up since April as well, though still well below previous peaks.

Biden tested positive for Covid on Thursday and is experiencing mild symptoms, Press Secretary Karine Jean-pierre said. A sample of the president’s Covid test was sent for sequencing and they’ll know the results within a week, according to the White House. The president has begun taking Pfizer Inc.’s Paxlovid treatment and will isolate at the White House while continuing his duties.

“We’re definitely in a surge or a spike,” said Wesley Long, medical director of microbiology at Houston Methodist Hospital. “Community transmission is very high, likely similar to what we experienced in the omicron wave in December.”

The surge highlights the challenges of dealing with a pandemic that has persisted for more than two and a half years and killed millions of people worldwide. BA.5 is particularly good at dodging immune defenses, so even some people who were infected just weeks earlier with another version may catch Covid again.

That immune evasion means that previous infections provide little to no protection and a recent vaccine or booster gains in importance, said Camille Nelson Kotton, an infectious disease specialist at Massachusetts General Hospital.

When people say, “Oh, I had Covid six months ago,’ I say, ‘That means nothing,’” Kotton said.

The current surge is driven by a new omicron subvariant, BA.5, which accounts for nearly 80 percent of cases now, and is marked by the greater decoupling of hospitalizations from cases.