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.”
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.
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.
‘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.
