Covid-19: what do we know about the new XD and XE combinations?

FOCUS- Classified under surveillance by the WHO and Public Health France, these new mutations of Sars-cov-2 could be very contagious, according to preliminary data.

While the masks fall, the Covid-19 continues to mutate. After the Omicron wave, the last major variant to date, two new combinations of Sars-cov-2 are the subject of increased surveillance: XD and XE. How do they spread? By simultaneous contamination of two different variants. When two stem viruses attack the same cell in a person, the enzyme then replicates the DNA of both the first and the second virus. Thus, XD originated from both Delta and Omicron. As for XE, the mutation comes from the two variants “cousinsfrom Omicron, BA.1 and BA.2.

Are these new forms of coronavirus more severe and/or more contagious? “Only the future will tell us», Comments Catherine Hill, epidemiologist at the Gustave Roussy Institute.

The XD variant, detected for the first time at the beginning of January 2022 in Cyprus, then arrived in the United Kingdom and France. As of April 4, 65 cases of “Deltacron” (mixture of Delta and Omicron) had been reported in France, indicated Public Health France in its last epidemic point.

The combination has been classified “being evaluatedby the WHO. A category confirmed by Public Health France on March 23, indicating that it was the subject of a “enhanced monitoringin France due to the severity of its Omicron and Delta strains, themselves considered “worrying“. But, says the agency,very little data is currently available on its characteristics”, and the recombinant XD represents “less than 0.1% of interpretable sequencesin flash surveys. For its part, XF has already been detected in 39 cases in the United Kingdom, but “it’s quite unlikely» that it is associated with higher transmissibility.

XE potentially ‘as transmissible as measles’

It is in the United Kingdom that the XE combination is most prevalent, with 1,200 cases recorded across the Channel. India, Thailand and New Zealand have also detected it on their territory, when only one case has been confirmed at this stage in France.

XE, a mixture of two stem cells of the virus, is one of the combinations that the WHO “keep watching“, According to a statement from the organization in early April. This could be even more transmissible than Omicron, itself already characterized by its rapid contagiousness. According to scientists from the UK Health and Safety Agency (UKHSA), the combination could be “10% more contagious than BA.2», strain cousin of Omicron described as «hypercontagiousby AP-HP professor Rémi Salomon.

Australian Professor Adrian Esterman, a former WHO epidemiologist, analyzes in the Canberra Times newspaper that the XE will probably be the one that “will cause the most problems in the world», taking over from BA.2. In terms of contagiousness, “BA.2 was itself close to measles, our most contagious disease“, he explains, deducing that “the XE version of Omicron is now probably as transmissible as measles“. At this point, however, health authorities believe that there is “no alert», entrusts to the Figaro a source at the Ministry of Health.


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