21 June 2022

The Rabbit Died

It's been mentioned here a few times; some of the more exotic fringe 'scientists' were asserting nearly at the beginning of Covid-19 that it would, inevitably, devolve into another (the fifth) common cold virus. That was soon proven wrong with Covid-ε, Covid-γ, and, ultimately, Covid-δ which were all a tad more virulent, but less contagious. Then along came Covid-ο which proved to be spectacularly contagious, yet much less virulent (geezers excepted, of course).

In today's NYT (dead trees division), we find that the notion of viruses always devolving to more contagious, less virulent, strains to be proven spectacularly wrong.
"There's been this dominant narrative that natural forces are going to solve this pandemic for us," said Aris Katzourakis, an evolutionary biologist at the University of Oxford.

But there is no such natural law.
In the situation reported, it all began with a farmer in Australia who liked to hunt small game and, for reasons not explained, chose rabbits. It happens that rabbits aren't native to Australia, so he imported some for his farm. I suppose he expected to keep their numbers in check by shooting them with sufficient regularity. Turned out, he didn't. They multiplied like rabbits. Turns out, that's not just a meme.
Without natural predators or pathogens to hold them back, they multiplied by the millions, eating enough vegetation to threaten native wildlife and sheep ranches across the continent.
So, the authorities, with scientific assistance, found a virus that infected rabbits (and, so far, only rabbits).

The virus did a bang up job. But virulence began to decline. And then, it didn't.
Newer viral lineages killed more of the lab rabbits. And they often did so in a new way: by shutting down the animals' immune systems. The rabbits' gut bacteria, normally harmless, multiplied and caused lethal infections.
Dum, dah, dum dum.
"We don't know what the next step in evolution will be," Dr. Katzourakis warned. "That chapter in the trajectory of virulence evolution has yet to be written."
The scientists have said to prepare for another Covid Winter. Listen to them.

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