Some experts are warning that although evidence is still emerging, the highly concerning omicron variant is expected to overtake delta within weeks.

“I do expect omicron to displace delta in the coming weeks,” said Stephen Kissler, a disease modeler at the Harvard T.H. Chan School of Public Health, in a briefing Tuesday. “Unfortunately, just in time for the new year, we’re going to see quite a lot of omicron spreading.”

“The time frame for that is going to vary quite a bit” across the country, Kissler said. “In places that have already seen an increase in transmission, in the next six to eight weeks is pretty reasonable. … By the time we’ve detected the omicron variant, it’s already been in circulation for quite awhile, so that may even eat into that eight-week period.”