What to know about the omicron variant and subvariant BA.2

A more transmissible subvariant, BA.2, has become the dominant strain in the United States as the omicron surge has waned. Those most at risk are the unvaccinated and older than 75

The BA.2 “stealth” omicron variant is expected to soon become the dominant strain. Here is what you need to know about a possible new wave of infections. (Video: Brian Monroe, John Farrell/The Washington Post)

After emerging in November, the omicron variant spread rapidly across the globe because of mutations that allowed it to evade some of the immunity produced by vaccinations and previous infections. In midwinter, tens of millions of people in the United States, many of them fully vaccinated and boosted, were infected by omicron.

Now, a subvariant called BA.2, which has many mutations not seen in omicron, is posing a new threat and accounting for a swiftly growing share of cases in the United States, as it propels sharp case increases in Europe and Asia. Preliminary research suggests BA.2 is at least 30 percent more transmissible than omicron.

The Centers for Disease Control and Prevention estimated that, as of March 19, BA.2 accounted for 35 percent of new infections. The genomics company Helix, analyzing more current data, put its own estimate at 70 percent. Both estimates show a steady rise toward dominance of the subvariant.

The rise in BA.2 cases comes as federal health authorities have relaxed certain recommendations. On Feb. 25, the CDC updated its mask guidelines, which no longer recommend masking for most people in indoor public spaces in counties with low to medium levels of covid-19 community transmission and hospitalizations. Most of America is now classified at those lower levels. However, other prevention strategies, such as vaccinations, are still recommended.

Coronavirus: What you need to know

Where do things stand? See the latest covid numbers in the U.S. and across the world. In the U.S., pandemic trends have shifted and now White people are more likely to die from covid than Black people.

The state of public health: Conservative and libertarian forces have defanged much of the nation’s public health system through legislation and litigation as the world staggers into the fourth year of covid.

Grief and the pandemic: A Washington Post reporter covered the coronavirus — and then endured the death of her mother from covid-19. She offers a window into grief and resilience.

Would we shut down again? What will the United States do the next time a deadly virus comes knocking on the door?

Vaccines: The CDC recommends that everyone age 5 and older get an updated covid booster shot. New federal data shows adults who received the updated shots cut their risk of being hospitalized with covid-19 by 50 percent. Here’s guidance on when you should get the omicron booster and how vaccine efficacy could be affected by your prior infections.

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