Nearly half of all European countries have recorded increases in new Covid-19 cases in the past week, according to an NBC News analysis of data from the Johns Hopkins Coronavirus Resource Center.
Among the countries with the biggest recent surges are Finland, where new cases jumped by 84 percent in its weekly case total, to nearly 62,500 weekly cases; Switzerland, whose weekly total rose by 45 percent, to 182,190; and the United Kingdom, which had a 31 percent increase, to a weekly total of 414,480 new cases. Austria, Belgium, France, Germany and Italy have also recorded double-digit percentage increases in their weekly tallies.
The rising numbers are in contrast to trends in the U.S., where daily cases, hospitalizations and deaths continue to decline. The U.S.'s daily death toll has dropped by 29 percent in the last two weeks, NBC News' tally shows.
Lawrence Young, a virologist at the University of Warwick in England, said Europe's rise in infections is likely to be a result of the spread of the omicron subvariant known as BA.2, paired with waning immunity and the relaxation of mitigation policies.
"The U.S. certainly needs to take note and consider the impact of yet another more transmissible variant," Young said.
BA.2 is considered a subtype of omicron because although it has small variations that set it apart they're not enough for it to be a new lineage. Still, some research suggests BA.2 is even more transmissible than the original omicron strain.
Disease experts in the U.S. say they are indeed watching Europe's trends closely.
"There is certainly a risk that the U.S. could face another surge in cases, as Europe is seeing," Dr. Gavin Yamey, a professor of global health and public policy at Duke University, said in an email. "We have lower rates of vaccination and booster coverage than many European nations, so a surge here could translate into rising hospitalizations."
But experts aren't ready to say definitively that a major new Covid wave is on the horizon globally, nor that there's cause for immediate concern in the U.S. Rather, they believe it's time to be vigilant — and to act pre-emptively.
"We should take the opportunity provided by the current lull to prepare for a possible further wave or variant of concern," Yamey said. To do that, he added, the U.S. government should expand vaccination and booster coverage and ensure high-quality masks and rapid tests are freely available.
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Many European officials have recently announced the end of pandemic-related restrictions. U.K. Prime Minister Boris Johnson lifted all remaining restrictions last month, pledging that when future surges arise, the responses will rely on vaccines and treatments rather than lockdowns.
France also loosened many of its Covid rules Monday, which means people no longer have to show proof of vaccination to enter restaurants, movie theaters and other public spaces.
Germany, too, is set to lift most of its Covid mitigation policies next week, even though Health Minister Karl Lauterbach said Friday that the rise in cases is a "critical" situation. According to Germany's Robert Koch Institute, more than 250,000 new cases were reported Wednesday, a record for a single day. Nearly 250 deaths were recorded.
"We cannot be satisfied with a situation in which 200 to 250 people are dying every day, and the prospect is that in a few weeks, more people will die," Lauterbach told reporters, according to The Associated Press. "The situation is objectively much worse than the mood."
In the U.S., federal health officials have started basing risk assessments and public guidance on hospitalization rates rather than infections.
"This updated approach focuses on directing our prevention efforts towards protecting people at high risk for severe illness and preventing hospitals and health care systems from being overwhelmed," Dr. Rochelle Walensky, the director of the Centers for Disease Control and Prevention, told reporters last month.
In his State of the Union speech, President Joe Biden urged Americans to start resuming their pre-pandemic habits.
"I cannot promise a new variant won’t come. But I can promise you we’ll do everything within our power to be ready if it does," he said.
China, by contrast, continues to enact strict measures to stave off the virus's spread. It implemented new lockdowns in recent days in Shanghai and other cities where there have been Covid spikes.
Experts say China's surges differ from Europe's, however, because the Chinese population has lower levels of immunity against the omicron variant.
"They haven't deployed vaccines that are very effective against this particular variant, this omicron variant, and so they're very vulnerable to spread right now," Dr. Scott Gottlieb, the former Food and Drug Administration commissioner, said Monday on CNBC.
Michael Head, a senior research fellow in global health at the University of Southampton in England, said he "would not be surprised" if more countries start considering additional shots beyond a single booster in the months ahead.
"There are many claims that we're finished with the pandemic," Head said. "Alas, this particular novel coronavirus is nowhere near finished with us."