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New subvariant of Omicron accounts for 40% of cases in the U.S.

A new sub-variant of Ómicron is now driving COVID-19 outbreaks in the U.S.

In early December, the XBB.1.5 subvariant of Ómicron accounted for only 1.3% of all COVID-19 cases in the US. By the end of that same month, XBB.1.5 was responsible for 40% of cases in the U.S. according to data from the U.S. Centers for Disease Control and Prevention (CDC).

The percentage of cases attributed to XBB.1.5 doubled in the span of a week in late December, from 21.7% to 40.5%, according to the CDC.

The sudden growth of this variant is causing concern among health experts, who warn that this variant may have greater resistance to antibodies than previous strains.

The leader of the WHO's COVID-19 emergency team, epidemiologist Maria Van Kerkhove, explained today why this new subvariant of Omicron is triggering alerts:

XBB.1.5 has been detected in 29 countries so far, there may be more, it is difficult for us to track these sub variants of Ómicron in countries where sequencing is not available. It is a subvariant of Ómicron and is the most transmissible of those we have detected so far. The reason for this is mutation, it is a recombination of the BA2 sublineages that allows the virus to replicate easily. We are concerned about its growth, especially in countries in Europe and North America, specifically in the northeastern United States, where XBB.1.5 has already rapidly replaced all other circulating sub-variants.

The Public Health Agency of Canada said they continue to monitor and identify variants of COVID-19 in Canada, including sublineages of the Omicron variant, but that we are not seeing a similar trend to the U.S. at this time.

"At this time, it is too early to know if the XBB.1.5 variant is growing in Canada," the agency said.

"PHAC scientists continue to monitor cases in Canada and track developments internationally."

Not much is yet known about XBB.1.5 in particular, but early research has suggested that XBB and its sublineages are significantly better at evading antibodies generated by previous vaccines or infections.

"Laboratory-based preliminary evidence available suggests that XBB is the most elusive SARS-CoV-2 variant of antibodies identified to date," WHO stated in its epidemiological update on 19 October.

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