Washington, US
The Omicron subvariant XBB.1.5 might become a dominant strain in Europe in the upcoming months, said the European Centre for Disease Prevention and Control (ECDC), on Friday. This comes days after the United States Centers for Disease Control and Prevention (CDC) announced the number of COVID-19 infections caused by XBB.1.5 in the month of December increased from four per cent to 41 per cent. According to CDCâs data, the subvariant is also the cause of nearly 75 per cent of new infections in the northeast region of the US.
What is XBB.1.5?
The XBB.1.5 Omicron subvariant or the unofficially nicknamed âKrakenâ by some scientists, is also an offshoot of XBB which was first detected in the US last year in October and has recently been dubbed the most transmissible variant.
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According to Grace Roberts, a virologist at the University of Leeds in Britain, an additional mutation to its spike protein is what makes the subvariant different from its otherwise very similar predecessor XBB.1. Notably, this additional spike protein is the key that allows the virus into the bodyâs cells.
How transmissible is it?
A study by the Fred Hutchinson Cancer Center in Seattle, US conducted by virologist Trevor Bedford and his team, suggests that the subvariant has a reproduction number of 1.6 which means that on average every person infected with it will go on to infect 1.6 other people.
Meanwhile, according to recent estimates by the CDC, as of Friday (January 14), at least 43 per cent of all COVID-19 cases across the country have been due to XBB.1.5 which was at 30 per cent in the first week of January. Additionally, the ECDC said that citing the data from its modelling indicates XBB.1.5 could become the dominant strain in Europe in one or two months.
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The EU health agency said that currently, the subvariant in question only accounts for 2.5 per cent of European cases. Furthermore, the XBB.1.5 has been spreading at least 12.5 per cent faster than other variants in the US, said the ECDC.
So far, at least 38 countries have XBB.1.5 cases out of which 82 per cent are in the US, eight per cent in the UK, and two per cent are in Denmark, said the World Health Organization (WHO) following a rapid risk assessment, on Wednesday, reported AFP.
Additionally, the ECDC also noted the growth advantage that XBB.1.5 has over other Omicron variants which are 109 per cent in North America and 113 per cent in Europe. However, these figures come with âsignificant uncertaintyâ, the EU health agency added.
Why is it so transmissible?
Earlier this week, the WHO technical lead on Covid, Maria Van Kerkhove, said that the emerging XBB.1.5 variant is the most transmissible form of Covid and clearly had a âgrowth advantageâ over other forms of the SARS-CoV-2, the virus that causes Covid. Meanwhile, the ECDC believes that the most likely explanation for its transmissibility is the XBB.1.5âs spike protein mutation combined with its already very transmissible predecessor the XBB variant.
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âItâs likely there will be an increase in cases in the short term, though this will depend on the extent of XBB.1.5âs advantage and the various factors affecting SARS-CoV-2 transmission in general,â said Marlin Figgins, a University of Washington PhD student working in Bedfordâs lab, as per the Scientific American.
Mutations and resistance to antibodies
The variant XBB was also known for its ability to evade the human immune system. It is also worth noting that since the beginning of the pandemic, mutations have been known to help viruses escape detection by a personâs immune system. As mentioned earlier, with the XBB.1.5âs mutation being in its spike protein it can bind to cells better, replicate faster and spread more easily.
According to a report by the Scientific American, while the exact mechanism behind XBB.1.5âs increased transmissibility remains unknown it could be the subvariantâs F486P mutation which allows it to sneak past the bodyâs defence mechanism as effectively as it does. Notably, the aforementioned spike protein mutation is both the new variant XBB.1.5âs defining feature and the main difference from its parental XBB.
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According to WHO, Omicronâs XBB variants, alongside BQ.1 remain resistant to both antibodies built from vaccinations as well as previous infections. Last month, a study published in the journal Cell said that XBB.1 is 63 times less likely to be affected by existing antibodies when compared to the BA.2 subvariant and 49 times more resistant than the BA.4 and BA.5 subvariants.
Symptoms and severity
As the WHO continues to assess data on the subvariant, it said that so far it did not carry any mutations that are known to increase the severity of the disease. Similarly, Roberts from the UK also told AFP that there is no data that suggests the subvariant is âanymore harmful â in terms of severe disease and death than previous variantsâ.
In a recent interview, the American Medical Association (AMA) Vice President of Science, Medicine and Public Health, Andrea Garcia, said, âSymptoms with XBB 1.5 appear to be similar to the earlier Omicron variants, and those can range from cold symptoms to shortness of breath and low oxygen levels that require emergency medical attention.â
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She also pointed out that with the emergence and spread of new variants, the signs of symptoms of Covid seem different than what was seen earlier in the pandemic, referring to people losing their sense of taste and smell. The AMA VP said that while it still happens in some cases, it has become rare with the Omicron variant.
âThe experts generally believe that the symptoms of Covid have become less severe over time. That could be because they tend to remain in the upper respiratory tract and donât affect the lungs as much as earlier variants,â said Garcia.
Additionally, she went on to attribute this immunity and people reporting milder symptoms like cough, congestion and a headache in the US to having some level of immunity either from the vaccines or prior infection. However, since they can be confused with having a cold or flu the AMA VP recommends getting tested for Covid if one should experience any of these symptoms.
Should we be concerned?
According to a report by AFP, the University of Leeds virologist says there is âno cause to panicâ about the new subvariant and she does not believe that there is a need for âany drastic action at presentâ. However, Roberts noted that it is important for the countries to monitor the progression and spread of XBB.1.5.
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Similarly, even the ECDC said that while the Omicron subvariant has become a dominant strain in the US, that might not be the case for Europe as observed earlier by the âmajor differences in variant circulationâ throughout the pandemic.
Furthermore, WHO official Kerkhove, also noted that their concern is about how transmissible it is and although many parts of the world are witnessing further waves of infection it does not âtranslate into further waves of deathâ, which she has attributed to countermeasures such as vaccines.
(With inputs from agencies)
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