The new subvariant of Covid has caused a stir in the United States, where it continues to spread rapidly. Several cases have also been reported in the UK. What do we need to know about XBB.1.5?
This is another variant of the currently dominant Omicron variant of the coronavirus, which itself emerged in late 2021, displacing earlier virus mutations – Alpha, Beta, and Delta. “Omicron” has spawned a variety of sub-variants that are even more contagious than the original.
It is believed that the symptoms of XBB.1.5 are similar to the symptoms of previous versions of “Omicron”, but it is too early to say for sure. For most people, the symptoms are similar to a common cold.
XBB.1.5 is derived from XBB, which began circulating in the United Kingdom in September 2022, but health officials did not find sufficient reason to classify it as “cause for concern.”
XBB had a mutation that helped it “break through” the body’s immune defenses, but the exact same mutation reduced the virus’ ability to penetrate human cells. Professor Wendy Barkley of Imperial College London says that XBB.1.5 has a mutation known to geneticists as F486P, which restores the virus’ ability to enter cells without losing its ability to evade our immune system. This makes it easier for the virus to spread.
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According to Barkley, these changes in the viral genome can be likened to the rungs of an evolutionary ladder: as the virus evolves, it finds new ways to evade the host’s defenses. At the Sanger Institute near Cambridge, geneticists decode no fewer than 5,000 samples of viral genomes every week, trying not to miss the emergence of new variants.
According to a staff member at the Yuwen Harrison Institute, XBB.1.5 is most likely the result of someone being infected with two different versions of “Omicron” at the same time. “Part of the genome of one virus merged with a fragment of another – and then it started to spread in that form,” he explains.
On Wednesday, the World Health Organization (WHO) confirmed that the XBB.1.5 variant is more likely to grow and spread than other variants of the virus known to scientists. At the same time, WHO emphasizes that there is no reason to consider this subvariant more serious or harmful than the usual omicron. The World Health Organization has pledged to closely monitor laboratory research, hospital data and statistics on XBB.1.5 infections to better understand the impact of this infection on patients.
Experts estimate that over 40% of new coronavirus infections in the United States are caused by XBB.1.5, making it the dominant variant in the country. Moreover, as of early December, it accounted for only 4% of infections, meaning that XBB.1.5 quickly overtook previous Omicron variants.
In recent weeks, the number of hospitalizations due to Covid-19 infection has begun to rise in the United States, and the country’s authorities have once again launched a program for free virus testing. It is difficult to say for sure, but such a prospect seems possible. In 2022, Britain experienced five waves of “Omicron”, and further outbreaks of the disease are inevitable. According to the Senger Institute, as of December 17, the XBB.1.5 variant caused only one in 25 coronavirus infections in the United Kingdom. However, only nine samples of the new subspecies had been identified at that time, so a more accurate picture will have to wait.
Next week, the UK’s Health Security Agency is expected to release a report on the spread of different variants of the coronavirus in the UK. According to Professor Barclay, if the new strain spreads in the UK as it has in the US, healthcare providers should be prepared for an increase in cases requiring hospitalization. Health officials in the United Kingdom have already stated that their concerns about the “twindemic” – the simultaneous epidemic of Covidia and influenza – are justified. Both viruses are overwhelming already overburdened hospitals and clinics.
In recent weeks, the number of Covidia cases, hospitalizations and deaths in the United States has increased. Professor Barkley is not particularly concerned about the spread of the new sub-variant of the virus in the UK, as there is no evidence that XBB.1.5 will overcome the protection provided by vaccines against severe disease. There is concern about the uncertainty of the effect of XBB 1.5 on people in different risk groups – including patients with weakened immune systems, for whom vaccinations are less effective.
Professor Hunter currently sees no evidence that XBB.1.5 could be more dangerous than other variants of “Omicron”. Accordingly, the current variant is no more likely to cause hospitalization or death than the others. “It’s funny how everyone is focused on the possible emergence of new variants in China, while XBB.1.5 has appeared in the US,” he notes.
Professor David Heymann of the London School of Hygiene and Tropical Medicine admits there is still much to learn about the new strain. However, it is unlikely to cause serious problems in countries like the UK, which have a high vaccination rate and a history of infection control measures. What really worries scientists is China, where prolonged closures have reduced demand for vaccines and immunity to the virus remains quite low in the majority of the population. “China needs to share clinical information on infected people to see how the variant behaves in the unvaccinated population,” says Professor Heymann.