In the US, a new sub-variant of Covid is spreading rapidly and has already made a lot of noise. Several cases have already been reported in the UK, BBC reported.

What is XBB.1.5?

This is another version of the Omicron variant, which now dominates all over the world, which appeared at the end of 2021, displacing earlier virus mutations - Alpha, Beta and Delta. It has spawned many sub-variants that are even more contagious than the original.

The symptoms of most people infected with XBB.1.5 resemble the common cold.

Is XBB.1.5 more contagious or dangerous than earlier variants?

XBB.1.5 itself is descended from XBB that began circulating in the UK in September 2022, but health authorities have not found sufficient reason to classify it as 'of concern'.

XBB had a mutation that helped it "break through" the body's immune defenses, but exactly the same mutation reduced the ability of the virus to enter human cells.

But XBB.1.5 has a mutation known to geneticists as F486P, which restores the ability of the virus to enter cells without losing the ability to elude our immune system. This makes it easier for the virus to spread.

These changes in the genome of the virus can be compared to the rungs of the evolutionary ladder: as the virus develops, it finds new ways to bypass the defense mechanisms of the host organism.

According to the geneticists of the Sanger Institute near Cambridge, most likely XBB.1.5 appeared as a result of infection of one of the patients with two different versions of Omicron at once, while part of the genome of one virus merged with a fragment of another - and then the virus began to spread already in this form.

The World Health Organization (WHO) has confirmed that in terms of growth and spread, the XBB.1.5 variant has more prospects than other viral variants known to scientists so far.

WHO noted that there is no reason to consider this sub-option more serious or harmful than the usual Omicron.

Where is XBB.1.5 distributed?

Experts estimate that more than 40% of new coronavirus infections in the US are caused by XBB.1.5, making it the dominant variant in the country.

In recent weeks, the number of hospitalizations due to Covid-19 infection in the United States has begun to rise, and the country's authorities have again rolled out a program of free testing for the virus.

Are scientists worried about XBB.1.5?

The concern is uncertainty about what effect XBB.1.5 has on people at various risk groups - including immunocompromised patients who are less likely to benefit from vaccinations.