Mutations

BA.5, now dominant U.S. variant, may pose the biggest threat to immune protection yet The FDA recommended that Covid vaccine makers target two omicron subvariants — BA.4 and BA.5 — in new booster shots expected to come this fall. NBC News

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The coronavirus subvariant known as BA.5 accounted for nearly 54% of the country's Covid cases as of Saturday, according to the Centers for Disease Control and Prevention. A similar subvariant, BA.4, makes up 17% more.

Europe is at the center of a resurgence in Covid-19 infections as more people mix at large-scale events and travel, according to the World Health Organization. 

“We are seeing a much more intense wave of the disease passing through Europe again,” Michael Ryan, executive director of the WHO’s Health Emergencies Programme, said at a media briefing Wednesday. “And we will see it happen elsewhere -- we are already seeing it in South East Asia and in the eastern Mediterranean region as well.”

Overall, the number of Covid infections rose 30% globally in the past two weeks, with the omicron subvariants BA.4 and BA.5 driving the increase in Europe and the US. The agency said it was also following a new sublineage of subvariant BA2.75 which had been detected in India. 

The increase in cases in Europe during the summer -- when transmission should be more difficult because people are outside -- results from people swapping one kind of mixing for another, such as attending large concerts and traveling more, Ryan said.  

In a sign of how the new coronavirus wave continues to spread across California, two-thirds of the state’s counties are now in the high COVID-19 community level, in which the U.S. Centers for Disease Control and Prevention recommends universal masking in indoor public spaces.

This comes as health officials are warning of concerning weeks ahead as two new ultra-contagious Omicron subvariants — BA.4 and BA.5 — spread. Experts believe the subvariants, which are not only especially contagious but also capable of reinfecting those who have survived earlier Omicron infection, are a major factor behind the continued persistence of coronavirus transmission across California.

So far, Los Angeles County health officials have not imposed new masking rules. But they have warned that might be necessary, perhaps later in July, if new coronavirus-positive hospitalizations continue to rise. Though experts are concerned, there is still uncertainty about how serious a summer wave will get.

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