Two strains of the new coronavirus are spreading around the world,
according to an analysis of 103 cases. But the World Health Organization insists that “there is no evidence that the virus has been changing”. So how many strains are there, and why does it matter?
Viruses are always mutating,
especially RNA viruses like this one, coronavirus SARS-CoV-2. When a person is infected with the coronavirus, it replicates in their respiratory tract. Every time it does, around half a dozen genetic mutations occur, says Ian Jones at the University of Reading, UK.
When Xiaolu Tang at Peking University in Beijing and colleagues studied the viral genome taken from 103 cases, they found common mutations at two locations on the genome. The team identified two types of the virus based on differences in the genome at these two regions: 72 were considered to be the “L-type” and 29 were classed “S-type”.
A separate analysis by the team suggests that the L-type was derived from the older S-type. The first strain is likely to have emerged around the time the virus jumped from animals to humans. The second emerged soon after that, says the team. Both are involved in the current global outbreak. The fact that the L-type is more prevalent suggests that it is “more aggressive” than the S-type, the team say.
