The Centers for Disease Control and Prevention's airport screening program has detected multiple cases of the new COVID-19 variant NB.1.8.1, which has been linked to a large surge of the virus in China. 

Cases linked to the NB.1.8.1 variant have been reported in arriving international travelers at airports in California, Washington state, Virginia and the New York City area, according to records uploaded by the CDC's airport testing partner Ginkgo Bioworks.

Details about the sequencing results, which in recent weeks on the GISAID, or Global Initiative on Sharing All Influenza Data, virus database, show the cases stem from travelers from a number of countries, including Japan, South Korea, France, Thailand, the Netherlands, Spain, Vietnam, China and Taiwan. The travelers were tested from April 22 through May 12, the records show.

Cases of NB.1.8.1 have also now been reported by health authorities in other states, including Ohio, Rhode Island and Hawaii, separate from the airport cases. In California and Washington state, the earliest cases date back to late March and early April.

Experts have been the variant, which is now dominant in China and is on the rise in parts of Asia. Hong Kong authorities say that rates of COVID-19 in the city have climbed to the worst levels they have seen in at least a year, after a "significant increase" in reported emergency room visits and hospitalizations driven by COVID-19.  

"CDC is aware of reported cases of COVID-19 NB.1.8.1 in China and is in regular contact with international partners," a CDC spokesperson said in a statement.

The spokesperson said that, so far, too few U.S. sequences have been reported of NB.1.8.1 to be included in the agency's  dashboard.

While authorities in Hong Kong there is no evidence that the variant, a descendant of the XDV lineage of the virus, is more severe, they have begun urging residents to mask when in public transportation or crowded places as cases have climbed.

Health authorities in Taiwan have a rise in emergency room visits, severe cases and deaths. Local health authorities say they are stockpiling vaccines and antiviral treatments in response to the epidemic wave.

Preliminary from researchers in China suggest the NB.1.8.1 variant is not better at evading the immune system compared to other strains on the rise, but it does have a greater ability to bind to human cells, suggesting it could be more transmissible.

"A more predictable pattern"

The strain came up multiple times during a Thursday of the Food and Drug Administration's outside vaccine advisers, as they wrestled with whether and how to recommend updating COVID-19 vaccines for the coming fall and winter seasons.

Vaccines from last season targeted a descendant of the JN.1 variant called KP.2. Early data presented to the committee by Pfizer and Moderna suggested switching to a different JN.1 descendant that has been dominant in recent months, called LP.8.1, could boost protection against NB.1.8.1, too. 

"The LP.8.1 vaccine has the highest titers against LP.8.1, which is dominant in the U.S. and many other regions and cross-neutralizes other currently circulating variants, including NB.1.8.1, a dominant JN.1 subvariant in many Asian countries," Darin Edwards, lead of Moderna's COVID-19 program, told the panel.

The committee unanimously backed recommending that the coming season's vaccines should target some kind of JN.1 variant, but was split on the details. Some favored allowing vaccine makers to stick with last season's vaccines, while others called for the update to target the LP.8.1 descendant of JN.1 that Pfizer and Moderna have prototyped.

"Although one can't predict evolution, and you don't know how this is going to keep diversifying, the overwhelming odds are that what does come and predominate in the next few months, the next six months, next year will come from something that's circulating now. It won't come from something that doesn't exist any longer," Jerry Weir, director of the FDA's division of viral products, said.

For now, CDC and FDA officials told the panel that only one strain — a variant called XFC — has been significantly growing in the U.S. But they cautioned that the evolution of the virus has been unpredictable, even as the country has settled into a relatively predictable pattern of two surges a year: once in the summer and once over the winter.

This past season only saw an evolutionary "drift" in the virus, as opposed to the kind of sweeping replacements driven by highly mutated strains in some earlier years. While COVID-19 trends climbed over the winter, they remained far below previous peaks.

"Throughout this winter, we didn't see that strain replacement that we have in the past couple of years. But I'm not saying that the virus will not shift again in the immediate future," the CDC's Natalie Thornburg told the panel. Thornburg is the acting chief of the laboratory branch in the CDC's division for coronaviruses and other respiratory viruses.

Rates of COVID-19 have now fallen back to low levels nationwide, measured through and .

"I do think after five years now, we are seeing very distinct patterns that [are] falling into a more predictable pattern," Thornburg said, citing a "seasonality analysis" that the agency has been working on about the virus.