With omicron cases increasing sevenfold in a single week, according to CDC, many health experts are suggesting Americans reconsider their holiday plans.

The omicron variant: The 'good,' 'bad,' and 'ugly' scenarios

'Spreading at a rate we have not seen with any previous variant'

For the week ending in Dec. 4, omicron accounted for 0.4% of all Covid-19 cases in the United States, according to CDC data. By the end of the following week, that number increased to 2.9%, and according to CDC Director Rochelle Walensky, some areas of the country like New York and New Jersey are attributing more than 13% of new cases to omicron.

At Houston Methodist's hospital system, omicron accounted for 13% of new cases in the four days leading up to Dec. 8, according to James Musser, chair of pathology and genomic medicine. Musser said he anticipates that number will get close to 20% when new data is published on Wednesday.

Musser said Houston Methodist is ready for an omicron wave. "We've had 21 months of this now, and we're sort of—I hate to say it, because it's tragic—but we're sort of skilled in the art of how to handle this," he said.

In a news briefing Tuesday, World Health Organization director general Tedros Adhanom Ghebreyesus said omicron "is spreading at a rate we have not seen with any previous variant," adding that even if omicron cases are less severe, "the sheer number of cases could once again overwhelm unprepared health systems."

In a briefing on Tuesday, federal health officials presented two scenarios based on modeling analyzed by CDC. The worst-case scenario showed what one federal official described to the Washington Post as a "triple whammy" with omicron cases coming on top of delta and influenza cases.

The second scenario outlined a smaller surge of omicron cases occurring in the spring, and as of now, it's unclear which scenario is more likely to occur, the Post reports.

"I'm a lot more alarmed. I'm worried," said Marcus Plescia, CMO for the Association of State and Territorial Health Officials who participated in the briefing.

"The hope is that [omicron] is going to be less severe, but the concern is that the numbers could be so great, even if proportionally less people have to be hospitalized, the numbers are much higher and a lot of people are going to be really sick and overwhelm things," Plescia added.

One federal health official familiar with the briefing told the Post that CDC is "considering the information at the highest levels right now, and thinking through how to get the public to understand what the scenarios mean. It looks daunting."

"The implications of a big wave in January that could swamp hospitals … we need to take that potential seriously," the official added.

What omicron's spread could mean for the holidays

Omicron's rapid spread throughout the United States has some health experts urging Americans to reconsider their holiday plans.

"Personally, I'm reevaluating plans for the holidays," said Bronwyn MacInnis, director of pathogen genomic surveillance at the Broad Institute of MIT and Harvard University. "It's the responsible thing to do and what feels right given the risk."

"At the rate that [omicron] seems to be spreading, there isn't a surveillance system on the planet truly that could keep up with it," MacInnis added.

The omicron variant has been moving "faster even than the most pessimistic among us thought that it was going to move," said Jacob Lemieux, an infectious disease expert at Massachusetts General Hospital. "There's a high likelihood that it will come to your holiday gathering."

"It's time to step back and reevaluate," said Amy Barczak, a professor of medicine at Harvard Medical School.

"My family has changed our plans so that we are no longer going to be getting together with particularly vulnerable members of the family over the holidays the way we had been planning to do," she added.

Lemieux said that if people do decide to gather for the holidays, they should "do everything [they] can to conduct it as safely as possible," meaning they should stay outdoors as much as they can, mask when indoors, and ventilate indoor spaces by opening windows.

Lemieux added that at-home rapid tests could be helpful, but urged caution. "I think it's time to reevaluate whether a gathering is necessary and big gatherings are necessary," he said. (Joseph, STAT News, 12/14; Sullivan, The Hill, 12/14; Sun et al., Washington Post, 12/14; Gregory, New York Times, 12/15; Weise/Weintraub, USA Today, 12/15)