My thoughts on the govt announcement yesterday regarding a new viral strain potentially driving an increase in cases in London. The claim, at least from listening to the daily briefing seems to be based on the strain increasing in frequency more recently. 1/N

Cases have been rising exponentially in England- much of the increase being attributed to the South, although declines have slowed even in the North following easing of lockdown. Much of this is anticipated, and expected, given the behaviour of the virus. 2/N

SARS-CoV-2, like any other viruses mutates as it multiplies (albeit slower than influenza). Mutations occur randomly and most are 'neutral' - i.e. have little to no effect on transmission, ability to evade the natural or vaccine-related immune response

Having said that, few mutations have been shown to be less likely to be neutralised by plasma from patients infected by the usual (wild-type) virus. Whether this translates to a lower response to vaccines or higher risk of re-infection is unclear at the moment.

Also worth noting that just because a variant becomes more frequent in a region doesn't necessarily mean it offers a fitness advantage to the virus. Many mutations rise to different frequencies in different regions due to random processes. The frequency of strains varies globally