This sub-variant, which now represents 40% of new contaminations in the United States, still circulates very little in France.
2023 already has its new variant to watch out for. Three years after its emergence, Covid-19 continues to make people talk, with in particular the end of the “zero Covid” strategy in China, which raises the risk of a strong epidemic resumption within a population less exposed to the virus and insufficiently vaccinated. But it’s not just in Asia that the coronavirus is worrying.
The US Centers for Disease Control and Prevention (CDC)who track variant progression, reported last week that a new subvariant was increasingly circulating in the United States: XBB.1.5.
XBB.1.5 is descended from XBB.1, itself descended from XBB which is a recombination of BJ.1 and BA.2.75. To put it simply, it is the result of two sub-variants of Omicron, the majority variant in many countries around the world.
A meteoric rise in the United States
During the last week of 2022 (December 25 to 31), it was present in more than 40% of the data on the sequencing of positive tests for Covid-19. By comparison, it was only present in 3.7% of positive tests in the first week of December. Also according to the CDC, XBB.1.5 is the cause of 75% of Covid-19 cases in the northeast of the country.
“We had not seen a variant progress so quickly for several months,” said Pavitra Roychoudhury, director of sequencing of Covid-19 variants at the virology laboratory at the University of Washington School of Medicine.
“This is the first time that a recombinant has taken up so much space in a Western country”, emphasizes CNRS research director Samuel Alizon to our colleagues from Parisian.
A priori no more virulent than the other sub-variants
Dr. David Ho, professor of microbiology and immunology at Columbia University, discovered with his teams that XBB.1.5 was less likely to be neutralized by antibodies from people who had been infected or vaccinated, reports CNN. “Alarming” levels of immune escape that could compromise the effectiveness of anti-Covid vaccines, concludes the professor whose work has been published in the scientific journal Cell.
Added to this ability is that of easily binding to the ACE2 receptor present on human cells and which the virus uses as a gateway into the body. “It has a better ability to penetrate cells,” confirmed Pavitra Roychoudhury. Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, is nonetheless reassuring about the virulence of the subvariant.
“It does not appear to cause more serious disease and […] he has so much more immunity in the population that I don’t think it’s going to take off,” said the researcher on CNN.
The CDC, while suggesting that XBB.1.5 “may be more transmissible than other variants” is unable to say that it would cause more serious forms: “we are monitoring this variant closely to see to what extent our vaccines and treatments work against it.”
Still very little present in France
If no figure on the number of sequencing of the XBB.1.5 subvariant has been communicated by the CDC, its predominance over other mutations of the coronavirus is nevertheless established.
A situation that France does not know. Moreover, there is no mention of XBB.1.5 in the latest epidemiological bulletins from Public health France devoted to Covid-19. According to the Institut Pasteur contacted by our colleagues from Parisianonly about fifteen cases have been reported by sequencing in France.
