WHO Concerned About the Spread of ‘Most Transmissible’ XBB.1.5 COVID Variant

Test tubes labelled "COVID-19 Omicron variant test positive" are seen in this illustration picture taken Jan. 15, 2022. (Dado Ruvic/Reuters)

The World Health Organization (WHO) says it is concerned about the spread of the XBB.1.5 strain of COVID-19 across the world, calling it the “most transmissible” Omicron subvariant they have detected until now.

“We are concerned about its growth advantage in particular in some countries in Europe and in the U.S., in North America, particularly the Northeast part of the United States, where XBB.1.5 has rapidly replaced other circulating variants,” said Dr. Maria Van Kerkhove, the WHO’s technical lead for COVID-19, at a press conference on Wednesday. “Our concern is how transmissible it is … and the more this virus circulates, the more opportunities it will have to change.”

According to data from the U.S. Centers for Disease Control and Prevention, XBB.1.5 made up 40.5 percent of all infections in the country as of Dec. 31. Roughly a month earlier on Nov. 26, XBB.1.5 only accounted for 0.6 percent of infections.

The WHO did not release any data on the severity of XBB.1.5, and there is no indication at present that people who get infected become sicker than previous versions of the Omicron variant, Van Kerkhove said.

The organization’s advisory group which tracks COVID-19 variants is conducting a risk assessment on the strain and will soon publish it in the coming days, she confirmed. The subvariant has been detected in 29 nations.

Opportunities to Evolve

The more XBB.1.5 circulates, the more it will have opportunities to evolve, according to Van Kerkhove.

A recent paper posted by Japanese researchers stated that their findings suggest XBB, from which XBB.1.5 is descended, is the “first documented SARS-CoV-2 variant increasing its fitness through recombination rather than single mutation.”

The results suggest that XBB is “highly transmissible” and highly resistant to immunity that was induced by people having had breakthrough infections of the previous subvariants of Omicron.

According to Yunlong Richard Cao, a Chinese scientist and assistant professor at Peking University, XBB.1.5 has an additional change compared to XBB called the S486P mutation which gives it a “greatly enhanced” ability to bind cells via a receptor called ACE2.

Though the WHO is expecting further waves of infection around the world, Van Kerkhove said that this may not translate into more deaths.

‘Stunning’ Spread

In a Jan. 4 tweet, Ashish K. Jha, the White House COVID-19 Response Coordinator, called the surge of XBB.1.5 subvariant from 4 percent to 40 percent in just a few weeks a “stunning increase.”

Jha believes the subvariant is “probably” more immune evasive, even more than other Omicron variants. Since it binds more tightly to the human ACE receptor, XBB.1.5 “may be” more inherently contagious. As to whether the subvariant is more dangerous, he said, “we don’t know.”

Whether the United States will see an XBB.1.5 wave will depend on multiple factors like herd immunity. However, Jha is optimistic that the situation can be kept under control.

“So am I concerned about XBB.1.5? Yes. Am I worried this represents some huge set back? No. We can work together to manage the virus,” he said.

People have taken preventative measures to help boost their immune systems and prepared home-based early treatment protocols. A number of protocols have been recommended by various doctors and groups, including the Front Line COVID-19 Critical Care Alliance (FLCCC) and the World Council for Health.

Mimi Nguyen Ly contributed to this report.