Covid-19 cases are spiking as a new variant, which may be the most transmissible yet, spreads across the country.

Roughly 6,500 people in hospitals in the U.S. have tested positive for Covid-19, according to the CDC, more than double the number from one month ago, and more than 10,000 people have died from Covid in the last month, the highest four-week total since the summer.

The latest surge, likely worsened by holiday gatherings, comes as the number of vaccines administered hits a three-month lull despite ongoing pleas from public health officials. Roughly 15 percent of the U.S. has received an updated booster shot, according to the CDC, and only 38 percent of those over 65 years old have received the booster, leading public health officials to ponder the possible effects of the new strain.

POLITICO spoke with two infectious disease experts about what the new Omicron strain, XBB1.5, which now accounts for about 40 percent of U.S. cases and appears to be particularly prevalent in the Northeast, means for the country and how we got here.

The variant doesn’t seem to be driving up hospitalizations and deaths — but the risk to individuals is real.

Though Covid hospitalizations appear to be on the rise nationwide, experts don’t project this Omicron subvariant alone to cause a spike — forecasts from early data suggest they’ll remain fairly steady, Céline Gounder, an infectious disease specialist and senior fellow at the Kaiser Family Foundation, said.

Holiday travel, social gatherings and colder weather are factors in the rising hospitalization rate.

“This may be more transmissible, but it’s not necessarily translating into more hospitalizations and deaths in the population at large,” she added.

The prediction matches the data from Singapore, where a related subvariant recently became dominant but didn’t result in a spike in hospitalizations and deaths — though that country’s vaccination rate is higher than that of the U.S.

But some individuals — particularly people who are older or pregnant or have weakened immune systems — are at heightened risk from the virus, regardless of larger population trends.

“I’m a bit concerned with it just because it’s coupled with the extremely low booster rates of those over 65,” Katelyn Jetelina, epidemiologist and professor at the University of Texas Health Science Center, said. “Our most vulnerable aren’t as protected.”

And Covid remains a concern to the population as a whole, health experts have continued to emphasize. From long Covid to the ongoing disease threats of the flu and respiratory syncytial disease, risks remain.

And that’s why Gounder and Jetelina, among other health experts, continue to highlight the importance of vaccination, masking and testing in stopping the virus.

It matters that this variant is more transmissible than others, but overstating the risk could have downsides.

“We have to be careful about not overplaying the risk every time there’s a new variant because I think you are going to see fatigue — we already see fatigue,” Gounder said of the public’s attention to the pandemic. “So you have to be judicious about when you say this is truly a threat versus not.”

A subvariant like this isn’t surprising, and more of the same is likely to come, both experts said. “This virus continues to do what viruses do,” said Jetelina. “We’re going to continue to see this.” Viral strains that are better at infecting people than earlier versions will eventually become dominant in the population — until a more contagious variant enters the scene.

“Big picture, that’s exactly what you expect: that the virus that is more transmissible has an evolutionary advantage over other variants and will come to dominate in the population,” Gounder said.