Omicron XBB.1.5 subvariant, which is spreading rapidly in the United States, is the most transmissible subvariant of COVID-19 to date. Here is what we know about him.
• Read also: The number of cases of the XBB subvariant has doubled in the country
• Read also: Should we fear the new variant of COVID-19 XBB.1.5?
This subvariant was first detected in the United States in October and now accounts for more than 27% of infections in the country, according to the Centers for Disease Control and Prevention’s (CDC) variant tracker.
A total of 38 countries have reported cases of XBB.1.5, including 82% in the United States, 8% in the United Kingdom and 2% in Denmark, the World Health Organization (WHO) said in an assessment on Wednesday. rapid risk.
European Union health agency ECDC said this week that XBB.1.5 accounted for just 2.5% of cases in Europe.
It looks a lot like its predecessor XBB.1, but has an additional mutation in its spike protein, the virus’s famous entry key, Grace Roberts, a virologist at Britain’s University of Leeds, told AFP.
It is the most transmissible sub-variant to date, said this week Maria Van Kerkhove, WHO technical manager on Covid. It clearly has a “growth advantage”.
The most likely explanation for this advantage is the spike protein mutation, which comes on top of a recombination of an already highly transmissible strain, the ECDC said.
XBB.1.5 has a growth advantage over other Omicron variants of 109% in North America and 113% in Europe, the ECDC added, warning that these figures come with “significant uncertainty” .
The center added that the proportion of XBB.1.5 cases had doubled every nine days in the United States.
However, “there is no data to suggest that XBB.1.5 is more harmful – in terms of serious illness and death – than previous variants,” said Grace Roberts. WHO continues to evaluate the data, but, for the moment, XBB.1.5 does not carry any mutations known to increase the severity of the disease, also judged the agency.
Omicron’s “XBB” sublines are, alongside BQ.1, the most resistant to antibodies accumulated from vaccination and previous infections, according to the WHO.
A study published in the journal Cell last month found that XBB.1 was thus 63 times less likely to be neutralized by existing antibodies than the Omicron BA.2 subvariant.
It is also 49 times stronger than the BA.4 and BA.5 sub-variants, which are currently dominant in the UK and many other countries. According to American expert Eric Topol, new research has however shown that bivalent Covid vaccines can continue to be effective against him.
There is “no reason to panic” about XBB.1.5, said Grace Roberts.
“I don’t think we need to take any drastic measures at this time,” she said, while deeming it important to continue monitoring her progress.
For the ECDC, its rapid growth in the United States does not necessarily mean that it will become dominant in Europe, due to “major differences in the circulation of variants” between the two regions throughout the pandemic.
Last week, the French public health agency stressed that the circulation of this variant “at fairly low levels” in France did not currently cause “particular concern”.
Eric Topol also saw as “good news” the beginning of a decline in hospital admissions among the elderly in the American Northeast, where XBB.1.5 accounts for more than 70% of cases.
The WHO has decided not to name Omicron subvariants after the letters of the Greek alphabet.
But on Twitter, he was given the disturbing nickname “Kraken”. “I think it may cause unnecessary concern to associate a virus with a mythical giant sea creature!” Reacted Grace Roberts.
