The nation's leading infectious disease expert suggested that the Omicron variant is likely in the United States. While the variant has not yet been detected in the U.S., Dr. Anthony Fauci said he believes the mutated strain is already in the country.

"We have not detected it yet, but when you have a virus that is showing this degree of transmissibility, and you're already having travel-related cases that they've been noted in Israel and Belgium and in other places when you have a virus like this, it almost invariably, is ultimately going to go essentially all over," Fauci said during an appearance on Weekend TODAY Saturday.

The Omicron variant has scientists concerned because it has over 50 mutations, including roughly 30 to the spike proteins. Those mutations could make the virus more transmissible and could help the virus evade protection provided by vaccines.

"These are all maybes, but the suggestion is enough," Fauci said. "This is something we got to pay really close attention to and be prepared for something that's serious. It may not turn out that way, but you really want to be ahead of it."

The virus is already causing countries to restrict travel to South Africa, which is where it was first identified. While the United Kingdom has reported just two cases, officials have already banned travel to South Africa and several other African nations. The United States announced a ban on travel to South Africa, Botswana, Zimbabwe, Namibia, Lesotho, Eswatini, Mozambique, and Malawi starting on Monday (November 29).

Fauci stressed the importance of getting vaccinated against COVID-19 as the new strain spreads around the globe.

"It is absolutely essential that unvaccinated people get vaccinated, and the vaccinated people get boosters," Fauci said. "We know now clearly that when you get a booster shot ... you dramatically increase the level of protection."