Covid Live Updates: C.D.C. Lowers Estimate of Omicron’s Prevalence in U.S.


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Credit…Bing Guan/Reuters

The Centers for Disease Control and Prevention estimated that the Omicron variant now accounts for roughly 59 % of all Covid instances in the United States, a major lower from the company’s earlier estimate. The replace reveals how laborious it’s to trace the fast-spreading variant in actual time and the way poorly the company has communicated its uncertainty, specialists mentioned.

Last week, the C.D.C. mentioned that Omicron accounted for approximately 73 percent of variants circulating in the United States in the week ending Dec. 18. But in its revision, the company mentioned the variant accounted for about 23 % of instances that week.

In different phrases, Delta, which has dominated U.S. infections since summer season, nonetheless reigned in the United States that week. That may imply {that a} important quantity of present Covid hospitalizations had been pushed by infections from Delta, Dr. Scott Gottlieb, a former commissioner of the Food and Drug Administration, suggested on Twitter. Hospitalizations sometimes lag a number of weeks behind preliminary infections.

Experts mentioned they weren’t stunned by the revisions, on condition that the C.D.C.’s estimates are tough guesses, with a variety of doable values often called “confidence intervals.” Cases of Omicron can solely be confirmed by genetic sequencing, which is carried out on only a portion of samples throughout the nation.

And Omicron continues to be spreading extraordinarily quick.

Still, they mentioned the C.D.C. did a poor job speaking the uncertainty of its estimates.

“The 73 percent got a lot more attention than the confidence intervals, and I think this is one example among many where scientists are trying to project an air of confidence about what’s going to happen,” mentioned David O’Connor, a virologist on the University of Wisconsin-Madison.

Dr. O’Connor mentioned he initially thought the preliminary 73 % level estimate “seemed high.” The company got here up with the estimate based mostly on a “relatively small number of sequences,” he added.

“It’s like playing Name That Tune, and trying to say, based on just the first note, if the song is Ice Ice Baby by Vanilla Ice, or Under Pressure,” Dr. O’Connor mentioned. “Without more data it can be really hard to know which one it’s going to be.”

The new estimate of 59 % can also be a tough calculation, specialists mentioned, and can probably be revised in future weeks.

“I just want people to be very aware that that is an estimate, that’s not actually from sequence-confirmed cases,” mentioned Nathan Grubaugh, an epidemiologist on the Yale School of Public Health. “With Omicron in particular, it’s been very difficult to have any sort of projections, because things are changing just so so rapidly.”

Dr. Grubaugh, who’s monitoring possible Omicron samples in Connecticut, mentioned that the variant makes up greater than 80 % of instances there, although he additionally notes that the nation is heterogenous and the variant probably has a distinct prevalence in completely different locations.

“I don’t know how the C.D.C. built their algorithm, but human beings made these programs, and humans are fallible,” mentioned Massimo Caputi, a molecular virologist on the Florida Atlantic University School of Medicine. “At the end of the day you can predict as much as you want but you need to look at the numbers you have in your hand.”

Dr. O’Connor, who’s monitoring Omicron in Wisconsin, mentioned the variant made up half of instances on the University of Wisconsin–Madison campus in simply three days. “If I was making a betting prediction, it wasn’t so much that the number 73 percent was wrong, but the timing to get there was wrong,” he mentioned.

These predictions will probably develop into extra correct over time as extra knowledge on Omicron is collected.

More exact numbers will probably be wanted to well distribute Covid remedies. One of the nice challenges of Omicron is the variant’s capacity to thwart two of the three monoclonal antibody remedies, which might stop severe sickness in Covid-19 sufferers. As such, some hospitals have begun scaling again these remedies; directors at NewYork-Presbyterian, N.Y.U. Langone and Mount Sinai all mentioned they might cease giving sufferers the 2 remedies which are ineffective towards Omicron. But the medicine may nonetheless assist folks contaminated with Delta.

“If you still have those Delta cases, discontinuing monoclonals means all those people who would have benefited from them won’t be receiving them at all,” Dr. O’Connor mentioned.

Dr. O’Connor mentioned scientists and well being care suppliers must do a greater job of speaking the uncertainty in the predications they share with the general public. “Having the humility to acknowledge that there’s a lot that no one knows and is unknowable right now is going to be really important.”





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