This is a translation from CTV News.
In early December, the Omicron XBB.1.5 subvariant accounted for just 1.3% of COVID-19 cases in the United States. At the end of the same month, XBB.1.5 was responsible for 40% of cases in the country, according to the data US Centers for Disease Control and Prevention [CDC]).
The percentage of cases attributed to XBB.1.5 doubled in the space of a week at the end of December, from 21.7% to 40.5%, according to the CDC.
The sudden proliferation of this variant is causing concern among health experts, who warn that there may be greater antibody resistance than previous strains.
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The Public Health Agency of Canada (PHAC) told CTVNews.ca in an email that it continues to monitor and identify COVID-19 variants in Canada, including Omicron subvariants. , but that they do not see a trend similar to that of the United States at the moment.
“At this time, it is too early to tell if the XBB.1.5 variant is growing in Canada,” the agency said.
“PHAC scientists continue to monitor cases in Canada and monitor the evolving health situation internationally.”
What is XBB.1.5 and where does it come from?
XBB.1.5 is the latest in a long line of variants of SARS-CoV-2, the virus that causes COVID-19.
As it evolves, the virus develops new mutations that subtly alter its structure and plan of attack. The variants and sub-variants that take over are those that have developed mutations allowing them to better infect our cells or to evade antibodies. Since Omicron emerged, its strains have dominated COVID-19 infections worldwide.
It is currently unknown where XBB.1.5 originated, but scientists began warning of a new strain of Omicron in the fall.
In one October 27 press release, the World Health Organization (WHO) explained that XBB and its subvariants are actually a recombination of Omicron’s BA.2.10.1 and BA.2.75 subvariants. This means that the two variants have swapped genetic material to create a new version that has aspects of both, which can happen when two different variants co-infect the same cell.
As of October 17, the WHO said XBB has been reported in 26 countries. While XBB and XBB.1 were reportedly first identified in India before spreading to parts of Asia like Singapore, XBB.1.5 was first detected in the United States, New York and in Connecticut at the end of October, according to the Global Initiative on Sharing Avian Influenza Dataan international organization that aims to track and sequence variants.
According to CDC data, the XBB.1.5 variant began spreading rapidly across the United States in December. In the northeastern United States, the variant that has taken over is XBB.1.5 accounting for 72% of cases in New York and New Jersey, as well as 75% of cases in New England, according to the CDC.
What we know
Not much is yet known about the XBB.1.5 strain in particular, but early research has suggested that the XBB strain and its subvariants are significantly more likely to evade antibodies generated by vaccines or previous infection.
“Available preliminary laboratory data suggest that XBB is the most antibody-vulnerable SARS-CoV-2 variant identified to date,” the WHO said in its statement. October 19 update.
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A study published in the journal Cell in mid-December revealed that the BQ and XBB Omicron subvariants were much better at evading antibodies. Although these subvariants carry the same characteristic that allows Omicron to better bind to cell receptors to infect human cells, monoclonal antibodies capable of neutralizing the original Omicron variant were unable to stop these new variants, according to the study.
The results of a another study published on December 21 in the journal New England Journal of Medicine suggest that mRNA booster injections may be much less effective in knocking out XBB and BQ.1.1. In a test of serum samples from participants who received a bivalent booster injection, the level of neutralization was 12 to 26 times lower for XBB and BQ.1.1 compared to the original 2020 strain, and “neutralizing activity was the weakest against the XBB sub-variant”. However, the authors cautioned that their study was limited by a very small sample of around 35 participants.
Is it dangerous?
If the XBB.1.5 variant is more transmissible and can evade antibodies more easily than other variants, it could be more dangerous in terms of the number of infections, because a virus that infects more people is more likely to inflict damage or even death.
The WHO noted in its October statement that the data did not suggest that the XBB variant and its subvariants would cause more severe disease.
However, she added that the risk of reinfection appears to be higher with XBB than with other Omicron variants in circulation.
What is the situation in Canada?
XBB and its subvariants have been detected in Canada, but numbers are currently low. According to a risk assessment conducted by Public Health Ontario in early November, there were six cases of XBB and five cases of XBB.1 in Ontario between September 25 and October 22.
According to the most recent data from PHAC, the BA.5 strain and its subvariants were still the most dominant in Canada in mid-December, accounting for 92.5% of samples analyzed at that time.
A detailed analysis of the variants detected in Canada each week through genome sequencing indicates that the XBB.1.5 strain represented approximately 0.6% of the samples analyzed during the week of December 11.
During the same week, the BQ.1.1 subvariant, which is counted in the category of BA.5 by PHAC, accounted for 30.7% of the samples sequenced.
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