Claim: ‘It is mutating into a more deadly strain’
All viruses accumulate mutations over time and the virus that causes Covid-19 is no different. How widespread different strains of a virus become depends on natural selection – the versions that can propagate quickest and replicate effectively in the body will be the most “successful”. This doesn’t necessarily mean most dangerous for people though, as viruses that kill people rapidly or make them so sick that they are incapacitated may be less likely to be transmitted.
Genetic analysis by Chinese scientists of 103 samples of the virus, taken from patients in Wuhan and other cities, suggests that early on two main strains emerged, designated L and S. Although the L strain appeared to be more prevalent than the S strain (about 70% of the samples belonged to the former), the S branch of the virus was found to be the ancestral version. The team behind this research suggested that this may indicate the L strain is more “aggressive”, either transmitting more easily or replicating faster inside the body. However, this theory is speculative at this stage – there haven’t yet been direct comparisons to see whether people who catch one version of the virus are more likely to pass it on or suffer more severe symptoms.
Flu viruses are fundamentally different from coronaviruses in that they are constantly shuffling their genomes, which means they rapidly morph from one strain into another – that’s why flu vaccines are needed annually. Coronaviruses tend to be genetically fairly stable and so scientists don’t expect a sudden shift in the mortality rate of Covid-19. But the question of whether coronavirus will disappear, reappear in waves or simmer in the background as an endemic illness still remains to be answered.
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