The omicron variant accounted for 95.4 percent of U.S. COVID-19 cases diagnosed during the week ending on Jan. 1, according to the Centers for Disease Control and Prevention (CDC).
The new data shows how quickly the highly transmissible variant has taken over, displacing the previously dominant delta variant. Just two weeks earlier, in the week ending Dec. 18, omicron accounted for only 38 percent of U.S. cases, the CDC said.
The omicron variant has fueled a massive spike in cases, to over 400,000 per day nationwide, but there is mounting evidence that the variant, on average, causes less severe disease than previous variants.
Still, while most people will have mild cases, even a small percentage getting hospitalized poses a risk to the hospital system given the massive number of total infections.
About 100,000 people are hospitalized with COVID-19, according to a New York Times tracker, about the same as the peak from the delta wave over the summer, and the number is climbing quickly.
"These @CDCgov Omicron data have changed substantially over the past 4 weeks," tweeted Eric Topol, professor of molecular medicine at Scripps Research, referring to the 95 percent estimate. "Likely by now this is true."
Hospital leaders are warning that they are overwhelmed and urging people to take precautions. Hospitalizations are far more likely among unvaccinated people, and officials are also urging vaccinated people to get booster shots to lower their risk of infection, though two shots still provide important protection against severe disease.