Scientists say they can outline scenarios for how the virus could evolve, but variants remain Covid’s unknowable wild card. In two years, they have rewritten the script so radically, many researchers are cautious to venture educated guesses of how Covid-19 will play out.

“There are various scenarios and they vary between rosy and gloomy,” said John Moore, a virologist and professor at Weill Cornell Medicine in New York. He emphasized, colorfully, that anyone saying they knew for sure what would happen next was full of it.

Omicron has only reinforced the folly of foretelling.

“I have just been so humbled and surprised by these variants of concern and the number of unanswered questions we have about them, where they came from, why they arise,” said Dr. Joshua Schiffer, a virologist and mathematical modeler at the Fred Hutchinson Cancer Research Center in Seattle.