Because omicron appears to cause less severe disease than delta, its behavior has kindled hope that it could be the start of a trend that eventually makes the virus milder like a common cold.

It’s a possibility, experts say, given that viruses don’t spread well if they kill their hosts very quickly. But viruses don’t always get less deadly over time.

A variant could also achieve its main goal – replicating – if infected people developed mild symptoms initially, spread the virus by interacting with others, then got very sick later, Ray explained by way of example.

“People have wondered whether the virus will evolve to mildness. But there’s no particular reason for it to do so,” he said. “I don’t think we can be confident that the virus will become less lethal over time.”