A surge in coronavirus infections in Western Europe has experts and health authorities on alert for another wave of the pandemic in the United States, even as most of the country has done away with restrictions after a sharp decline in cases.

infectious-disease experts are closely watching the subvariant of omicron known as BA.2, which appears to be more transmissible than the original strain, BA.1, and is fueling the outbreak overseas.

Germany, a nation of 83 million people, saw more than 250,000 new cases and 249 deaths Friday, when Health Minister Karl Lauterbach called the nation’s situation “critical.” The country is allowing most coronavirus restrictions to end Sunday, despite the increase. Britain had a seven-day average of 65,894 cases and 79 deaths as of Sunday, according to the Johns Hopkins University Coronavirus Research Center. The Netherlands, home to fewer than 18 million people, was averaging more than 60,000 cases the same day.

In all, about a dozen nations are seeing spikes in coronavirus infections caused by BA.2, a cousin of the BA.1 form of the virus that tore through the United States over the past three months.In the past two years, a widespread outbreak like the one now being seen in Europe has been followed by a similar surge in the United States some weeks later. Many, but not all, experts interviewed for this story predicted that is likely to happen. China and Hong Kong, on the other hand, are experiencing rapid and severe outbreaks, but the strict “zero covid” policies they have enforced make them less similar to the United States than Western Europe.

A number of variables — including relaxed precautions against viral transmission, vaccination rates, the availability of antiviral medications and natural immunity acquired by previous infection — may affect the course of any surge in the United States, experts said.

Most importantly, it is unclear at this point how many people will become severely ill, stressing hospitals and the health-care system as BA.1 did.