SARS-CoV-2 Starts to Evolve More Asymptomatic Spread

The Delta strain of SARS-CoV-2 has a longer asymptomatic period than earlier strains: around a day more. This is because it becomes detectable by PCR in 1.5 fewer days than previous strains, on average, but that is slightly counterweighted by faster symptom onset. Thus, although overall, symptoms present themselves slightly more quickly than in other strains, this still allows for longer aymptomatic transmission.

https://www.nature.com/articles/d41586-021-02259-2

Although these mutations probably just generally facilitate spread, they demonstrate that the virus has the ability to adapt itself to our quarantine strategies.

SARS-CoV-2 has now demonstrated that it can modify both of these timepoints -- seroconversion and symptom onset -- independently, and it can probably modify each timepoint in either direction.

It's not clear just how long it can make its incubation or asymptomatic phases, though, because extension of that time could come at the cost of pathogenicity overload, since the immune system has longer to gear up. There may be enough compensatory mutations that allow it to reach a very short or long incubation period with very slow or fast onset of symptoms.

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