> Viruses don’t always become attenuated (less virulent). When they do, it’s because there is an evolutionary selection pressure driving it. No such pressure ex

> Viruses don’t always become attenuated (less virulent). When they do, it’s because there is an evolutionary selection pressure driving it. No such pressure exists for SARS-CoV-2. An example of this type of selection pressure would be a virus that is so virulent, it kills its host before it can be transmitted to another one. A virus is essentially a machine programmed to make more viruses. To do that, it needs to be spread to new hosts. So variants that are so virulent they kill a host before that host can pass it along, that is under negative selection pressure. The more virulent viruses won’t be passed on. But attenuated variants will. They are under positive selection. For SARS-CoV-2, this has never been an issue. This virus can be transmitted to a new host before an infected person develops symptoms. Even those who die from COVID are most contagious before they become severely ill. https://mobile.twitter.com/angie_rasmussen/status/1441416013883461640 https://mobile.twitter.com/angie_rasmussen/status/1441416013...