The U.S. is putting travel restrictions in place in response to a new variant of the coronavirus circulating in southern Africa. The restrictions, which are set to take effect on Monday, are being implemented out of an abundance of caution, said a senior Biden administration official.

The World Health Organization announced Friday that it deems this strain, B.1.1.529, a variant of concern, and has named it omicron. It's the first new variant of concern since delta.

The U.S. Centers for Disease Control and Prevention announced Friday night that no cases of omicron have been identified to date in the U.S., but that the agency has surveillance systems in place and it expects the variant will be identified quickly if it emerges in the U.S.

Here's what we know so far about the new variant — and what we don't.

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