"The XBB.1.5 recombinant is a lineage of the XBB lineage - one of the multiple lineages of the Omicron variant -, which, like XBB itself, is thought to be associated with escape from the immune system", explained INSA researcher João Paul Gomes.

On Wednesday, the World Health Organization (WHO) indicated that it was assessing the risk of the new XBB.1.5, which is spreading rapidly in several countries, such as the United States, where it already represents about 40% of cases of covid-19.

The WHO technical leader in the response to covid-19, Maria Van Kerkhove, went further and stated, in the press videoconference, that XBB.1.5 "is the most transmissible subvariant detected so far".

According to João Paulo Gomes, who is coordinating the study on the genetic diversity of SARS-CoV-2 in Portugal, the XBB.1.5 subline "may be associated with greater transmissibility, given its significant increase in frequency in some regions" of the world.

However, "it will be prudent to wait for its frequency evolution in multiple countries to understand its real epidemiological impact", said the INSA specialist.

For the researcher, "it is still early" to understand whether this subline will have any significant impact on hospitalizations due to Covid-19, as it is different from the other strains already in circulation of the Omicron variant.

XBB.1.5 is a two-stranded recombinant of BA.2 and was originally identified in October 2022. It has been detected in 29 countries.