The World Health Organization (WHO) indicated yesterday that it is assessing the risk of the new XBB.1.5 sub-variant of the covid-19 coronavirus, which is spreading rapidly in several countries and may be more transmissible.

The director-general of the WHO, Tedros Adhanom Ghebreyesus, said in a video press conference that the organization "is closely monitoring and assessing the risk" of this sub-variant, which "spreads rapidly", and "will report accordingly" as new data is obtained.

The XBB.1.5 sub-variant of the Omicron variant of SARS-CoV-2 results from a recombination of two BA.2 sub-strains and has already been detected in 29 countries, including the United States, where it already accounts for around 40% of covid-19 cases.

According to the US Centers for Disease Control and Prevention, this sub-variant "may be more transmissible", although it is not yet known whether it will have "more serious" effects.

The WHO's technical lead for the Covid-19 response, Maria Van Kerkhove, went further and said today at the press conference, quoted by AFP, that XBB.1.5 "is the most transmissible sub-variant detected so far".

The WHO Technical Advisory Group on the Evolution of the SARS-CoV-2 Virus said in a statement that it is assessing the "rapid increase in the proportion" of the sub-variant in the United States and other countries.

Covid-19 is an infectious respiratory disease caused by the SARS-CoV-2 coronavirus, a type of virus detected three years ago in China and which has spread rapidly around the world, taking on several variants and sub-variants, some more contagious than others.

The disease has been an international public health emergency since January 30, 2020 and a pandemic since March 11, 2020.