As the virus spread, more and more mutations appeared, giving rise to even more transmissible variants. First came Alpha, which was about 50% more infectious than the original virus, and soon Delta, which was, in turn, about 50% more infectious than the Alpha.
“We are now practically in a Delta pandemic,” said Robert Garry, a virologist at Tulane University. “So another push, another spread of a slightly better variant.”
While some experts have been surprised to see the hyperinfectious variant emerge so quickly, that it has more than a dozen notable mutations, the emergence of more transmissible variants is a manual of viral evolution.
“It’s hard to imagine that the virus will appear in a perfectly formed new species for this species,” said Andrew Read, an evolutionary microbiologist at Penn State University. “You have to do a little bit of adaptation.”
But scientists don’t expect this process to continue indefinitely.
There are probably fundamental biological limits to the degree of infection of a particular virus, depending on its intrinsic properties. Viruses that are well adapted to humans, such as measles and seasonal flu, do not consistently become more infectious, noted Dr. Bloom.
It is not entirely clear what the communicability constraints are, he added, but at least the new coronavirus cannot replicate infinitely fast or travel infinitely far.
“Transmission requires a person to exhale or cough or exhale the virus and land in someone else’s airways and infect them,” said Dr. Bloom. “There are only limits to this process. It’s never going to happen that I sit here in my office and give it to someone on the other side of Seattle, right? “
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