Omicron variant in the US: What we know

Here's what we know about the omicron variant of COVID-19 in the U.S. after its first case was announced Wednesday.

The person, who was identified as being between 18 and 49, is self-quarantining and has been since testing positive and all close contacts have been contacted and tested negative. The City and County of San Francisco COVID-19 Emergency Operation Center said the traveler is a resident of San Francisco who returned on Nov. 25. 

"We are still learning about the omicron variant, but we are not back to square one with this disease," Dr. Grant Colfax, the director of the San Francisco Department of Public Health, said in a statement. "From what we know now, San Francisco is relatively well-positioned to handle COVID-19 and its variants because of our high vaccination rates, our high booster uptake, and other local health measures such as masking and testing."

In a statement, the U.S. Centers for Disease Control and Prevention (CDC) explained that the individual was fully vaccinated and had mild symptoms that are improving. Dr. Anthony Fauci, America's top infectious disease expert, told reporters that the individual, who had the full two doses of the Moderna vaccine, tested positive on Nov. 29 and had yet to receive a booster shot.