Since the appearance of Omicron in 2021, which is one of the variants of covid - 19, a new variant with a high speed of spread and transmission of infection that the world has not seen before is coming to us ،

This variant is called XBB 1.5 by scientists "xBB 1.5", which belongs to the SAR-Kov-2 strain of coronavirus.

Its extremely rapid spread, despite the immunity of vaccinated people, worries the world's medical community.

It is spreading very rapidly in the United States. In about a month, its transmission rate jumped from 5 percent to 40 percent.

"We have never seen such a speed of transmission before, it's amazing," emphasizes Lawrence Young, a virologist at the British Warwick Medical School, the same conclusion reached by the World Health Organization, which on Wednesday called xbp 1.5 "the most contagious mutant".

And this strain is a third and even a fourth version of the SAR-cov2 virus, considering that it's not just about a single variant of covid-19. "It's a mutation of a combination of Omicron mutants," explains Jonathan Stowe, virologist and director of research at the Francis Crick Institute in London.

Unlike strains that are generated with mutations in the most widespread viruses, each separately, the new mutant is generally formed "in the body of an infected person with several mutations merging among themselves," explains Lawrence young.

The new variant is characterized by two characteristics, namely its great resistance to the vaccine and also the immunity that may have been formed after infection with Omicron. It also easily and strongly fixes itself on the cells of the human body to infect them" with the disease, according to young.

This resistance that characterizes it is not new, "it was actually present in the other sub-mutants of XBB and the new mutation did not change it," emphasizes Simon Clark, researcher in infectious diseases at the University of reading. But, the British researcher continues, the big change occurs mainly in the 486th position of the genetic code of the virus, where "the spike protein, the well-known key that allows the virus to open the door of cells, is transformed to easily bind to the receiving area".

This change is what causes the infection to spread so widely. "If you have a virus that infects cells easily, you need fewer pathogens to infect another person," summarizes Simon Clark, who points out that there could also be other factors that accelerate the spread of infection, (for example if this variant causes frequent coughing).

The question remains about how virulent this virus is. The outbreak of" xbp 1.5 " in the United States somewhat affected the capacity of hospitals in the United States, which as a result increased by more than 4 percent compared to the previous week, as is the case of intensive care units, which recorded an increase in the number of patients by 9 percent.