The World Health Organization (WHO) issued a recommendation on January 10, urging countries to encourage passengers on long flights to wear masks due to the swift rise in cases of the XBB.1.5 Covid-19 variant, nicknamed the “Kraken” after a mythical sea creature.

The XBB variants, including XBB.1.5, have evolved to better evade antibodies from previous infections and vaccinations. XBB.1.5, in particular, carries a mutation known as F486P, which researchers believe enhances its ability to bind more effectively to human cells. This variant originates from the Omicron family, specifically from a recombination of the BA.2.10.1 and BA.2.75 versions, which occurs when a person is infected with both at the same time.

At a press briefing, Dr. Catherine Smallwood, the WHO’s senior emergency officer for Europe, recommended that masking on long flights be encouraged, especially for passengers arriving from regions with significant Covid-19 transmission.

In the first week of January, the XBB.1.5 variant accounted for over 27% of Covid cases in the United States. Dr. Andy Pekosz, a professor at Johns Hopkins Bloomberg School of Public Health, noted that lab studies suggest the bivalent vaccines remain effective at preventing severe illness, although their ability to prevent infection might be less robust.

XBB.1.5, first identified in October, has driven a surge in Covid cases in the U.S., making it the most transmissible Omicron sub-variant so far. It has also begun spreading in Europe, with WHO Director-General Dr. Tedros Adhanom Ghebreyesus confirming that the variant has been detected in over 25 countries.

Rising case numbers in both the U.S. and China, where restrictions have been relaxed, have heightened concerns among health officials. Dr. Smallwood emphasized the importance of reviewing the data for pre-departure testing but stressed that any travel-related measures should be applied equally, without discrimination.

While the WHO is not currently recommending testing for travelers from the U.S., experts continue to monitor the situation. It remains unclear whether XBB.1.5 will lead to a global surge in severe cases, but health professionals affirm that current vaccines offer protection against serious illness, hospitalization, and death. Data indicates that bivalent vaccines, already administered in Singapore, provide good defense against XBB-related infections.