Reply To: SARS cov2 and Covid 19


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#64144
Clark

I hear that further papers are showing the new variant to be 50% to 70% more infectious, ie. its R-zero number is higher.

R-zero is the reproductive number for a strain of the virus, whereas the R that is in the news a lot is R-t, the reproductive number actually manifested in a specific population with specific behaviours. Social restraint reduces R-t; it does not affect R-zero. All else remaining the same however, increased R-zero does increase R-t.

The “news” was forever on about “getting R less than 1” so that infection prevalence would decrease, “R” meaning R-t for the old strain. But the new variant has a higher R-zero, so more social restraint will be needed to get it’s R-t below 1. If the new variant has 50% greater infectiousness, the R we’ve heard so much about will now have to be reduced below 0.67 for infection prevalence to go into decline.

During the spring/summer restrictions, R never fell below 0.67 in England. In Scotland, R may have been pushed as low as 0.5.

In short, the restrictions we had from spring onwards won’t work for this variant, at least not in England.