The Centers for Disease Control and Prevention on Tuesday estimated that the Omicron variant was responsible for about 59 percent of COVID cases nationwide in the week ending Dec. 25, reports The New York Times, “a significant decrease from the agency’s previous estimate.” Experts told the Times that such revisions reveal “how hard it is to track the fast-spreading variant in real time and how poorly the agency has communicated its uncertainty.”

Last week, the CDC estimated that Omicron accounted for approximately 73 percent of cases for the week ending Dec. 18, but has now had to revise that down to 23 percent.

A CDC spokesperson said the issue was due to how fast Omicron’s been spreading, per Politico.

“There was a wide predictive interval posted in last week’s chart, in part because of the speed at which Omicron was increasing,” said CDC spokesperson Jasmine Reed. “We had more data come in from that timeframe and there was a reduced proportion of Omicron.”

Experts “were not surprised” by the CDC’s revisions, given the estimation process, but felt the agency “did a poor job” conveying the uncertainty of it all, writes the Times.

“I think this is one example among many where scientists are trying to project an air of confidence about what’s going to happen,” said virologist David O’Connor.

That said, this current estimate of 59 percent is also likely to change, experts noted.

“I just want people to be very aware that that is an estimate, that’s not actually from sequence-confirmed cases,” added epidemiologist Nathan Grubaugh. “With Omicron in particular, it’s been very difficult to have any sort of projections, because things are changing just so so rapidly.” Read more at The New York Times.