Many virologists thought this very unlikely, you could never know that a new variety had higher transmission from mere incidence data: you must understand the biological mechanism. Are they correct? Obviously not.

Why did they think that a new, more transmissible variant of COVID-19 was unlikely? There are several reasons. One, they typically deal with viruses that have been around for a long time, like measles ( > 1000 years). An old virus is going to be pretty well-adapted to to humans. Probably it’s at a local optimum, where small changes would reduce infectivity. But you don’t expect that high degree of optimization in a virus that’s brand new in humans: while spreading to very many people, more than 100M, greatly increases the chance of transmission-increasing mutations. Fisherian acceleration.

Like most biologists and MDs, most virologists don’t know any theory, and in fact don’t _believe_ in theory. For this they occasionally pay a price.

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