World Health Organization officials said countries should consider advising passengers to wear masks in high-risk environments such as long-haul flights in light of the rapid spread of a new variant of the new coronavirus, Omicron strain XBB.1.5, in the United States, Reuters reported.

Catherine Smallwood, a senior official at WHO's European Office of Emergency Services, pointed out at a news conference in Geneva on 10 October that XBB.1.5 is now spreading rapidly in the United States and that the number of XBB.1.5 cases detected in Europe is small, but continuing to increase.

Reuters said XBB.1.5 is considered to be the most infectious variant of the Omicron subtype strain at present. According to current genetic analysis of the virus, XBB.1.5 has spread mainly in the United States and Europe, where it has been found in at least 29 countries and territories.

Reuters quoted U.S. health officials as saying that XBB.1.5 accounted for about 27.6 percent of new crown infections in the United States in the week ending Jan. 7.

Currently, some European countries have adopted preventive entry restrictions. In response, WHO Regional Director for Europe Hans Kruger said on 10 January that countries are justified in taking precautionary measures to protect people from the virus, but he also called on countries taking action to ensure that such measures are science-based, appropriate in strength and not discriminatory.

Recently, a new variant of the Omicron strain XBB.1.5 has raised concerns.

Maria van Kerkhoff, technical director of WHO's health emergency program, said on April 4 that XBB.1.5, first discovered in October last year, is more infectious than any previously known mutant strain and has immune escape, and like other mutant strains of the Omicron subtype, the more it spreads, the more chance it has to mutate.

Also according to a previous WHO statement, infection with XBB is still dominated by respiratory symptoms, mainly including fever, nasal congestion, sore throat, headache and fatigue, similar to those of BA.5. Translated with www.DeepL.com/Translator (free version)