The US Center for Disease Control and Prevention (CDC)'s airport screening programme has identified 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 and is spreading in several parts of Asia.

International travellers arriving at airports in California, Washington state, Virginia, and New York City have tested positive for the NB.1.8.1 variant, according to data from the CDC's airport testing partner, Ginkgo Bioworks, CBS News reported on Thursday.

Sequencing data recently published on the Global Initiative on Sharing All Influenza Data (GISAID) database reveal that the NB.1.8.1 cases originated from travellers arriving from several countries, including Japan, South Korea, France, Thailand, the Netherlands, Spain, Vietnam, China, and Taiwan.

According to the records, these travellers were tested between April 22 and May 12.

More transmissible

Health authorities in additional states, including Ohio, Rhode Island, and Hawaii, have also reported cases of the NB.1.8.1 variant, separate from those identified through airport screenings.

In California and Washington state, the earliest detected cases date back to late March and early April.

The NB.1.8.1 variant, now dominant in China and spreading in parts of Asia, has caused a rise in COVID-19 cases and hospitalisations in Hong Kong and Taiwan.

Although it is not believed to cause more severe illness, officials are advising mask use in crowded places and increasing vaccine and treatment supplies.

Early studies suggest the variant is more transmissible due to stronger binding to human cells, but it does not significantly evade immunity compared to other strains.