BA.4 and BA.5 power a surge of known infections in Europe, officials say.

The rapidly spreading Omicron subvariants known as BA.4 and BA.5 are driving a summertime surge of the coronavirus in Europe, health officials say, after most Covid policies were removed in spring and a more relaxed approach to the pandemic has become the norm during the warmer months.

Known cases in Europe rose to 57 cases per 100,000 as of Wednesday from 33 cases per day per 100,000 just two weeks earlier, according to the Center for Systems Science and Engineering at Johns Hopkins University. That is the sharpest increase – a rise of about 70 percent – of any region of the world over the same period.

BA.4 and BA.5 appear to be able to evade some antibodies from previous infections and vaccines, but research suggests the subvariants do not seem to cause more severe disease. BA.5 is already dominant on its own among new US cases, according to federal estimates.

Dr. Michael Ryan, the executive director of the World Health Organization’s Health Emergencies Program, said on Wednesday that the wave hitting Europe now could be worse than it seems and pointed to what he called “almost a collapse in testing” that could be obscuring the true spread of the virus.

Dr. Ryan added that while many European countries have seen an uptick in hospitalizations, “what we’re not seeing is an increase in intensive care unit admissions, so the vaccines are still very much working.”

While much of the world has dropped mandatory pandemic safety measures, a few areas have sometimes reversed course. On Friday, the Mediterranean island of Cyprus reinstated indoor mask mandates. And on Monday, France’s fifth-largest city, Nice, will require masks on public transportation, which goes beyond the central government’s recommendation. On the other hand, Austria recently discarded a vaccine mandate that it never enforced.

Professor Lawrence S. Young, a virologist and professor of molecular oncology at the University of Warwick, told The New York Times that he does not think that masking restrictions will return to Britain. One exception he sees is at hospitals, many of which have reintroduced mandatory mask-wearing in recent weeks as cases have been rising.

For most Britons, Dr. Young thinks pandemic fatigue has set in. “I think this idea of ​​trying to persuade people to take personal responsibility is not working,” he said.

France and Cyprus join Austria, Britain, Germany, Greece, Italy, and Switzerland as hot spots, according to the Our World in Data project at the University of Oxford. On Thursday, Sweden’s health minister, Lena Hallengren, noted at a news conference that cases were rising “even though we are in the middle of the summer.”

Dr. Ryan said that while transmission should be more difficult because many people are outdoors for longer, there has been a return of crowded events like concerts and more travel. Especially hot temperatures can also drive people indoors.

In Portugal, where vaccination rates are higher than in the United States, cases rose sharply after BA.5 became dominant in May, and hospitalizations neared their previous Omicron peak, though they have subsided.

The European Medicines Agency, the European Union’s main drug regulator, said on Thursday that confirmed infections in the region could remain high for weeks, as the BA.4 and BA.5 are projected to become dominant in the region by the end of July. That assessment echoed a recent prediction made by the European Center for Disease Prevention and Control.

“We are in a much better position than we were in previous waves of infections,” said Dr. Marco Cavaleri, head of vaccine strategy at the European Medicines Agency, adding that vaccinations have helped.

The agency said it had begun reviewing emerging data for vaccines with new compositions and was working to clear updated vaccines by September, Dr. Knights said. But given the difficulty of predicting which version of the virus would be circulating by the fall, the agency was still in touch with vaccine manufacturers and considering the best approach.

“For the time being we still think it’s very good to keep all options open,” Dr. Knights said. In the United States, federal regulators have already recommended that vaccine manufacturers update boosters to target BA.4 and BA.5, eyeing a fall booster campaign.

Dr. Young, too, is looking ahead to the fall. “I think there’s a worry about there being a perfect storm over the autumn, winter with new variants, which are almost inevitable, of Covid, flu and other respiratory infections,” he said.

The European Medicines Agency, along with the European Center for Disease Prevention and Control, recommends that people over 80 years old get a second booster, and those over 60 get a second booster when infection rates rise. Both are considering whether to recommend a second booster more widely for the public, Dr. Knights said on Thursday.

Alain Delaquérière and Sarah Cahalan contributed reporting.

Leave a Comment