Wouldn't you know it, the first known case of the Omicron variant of COVID to arrive in the U.S., via South Africa, is in San Francisco.

The patient, who's reportedly experiencing mild symptoms so far, tested positive for COVID after traveling back to the Bay Area from South Africa on November 22 and subsequently feeling ill, as KPIX is reporting. It was quickly discovered that this was an infection with the new and highly mutated Omicron variant — a discovery that was reportedly made and confirmed by UCSF and the CDC on Wednesday, December 1, after a positive test was first found and flagged on November 29.

The individual, obviously, has not been identified, and is self-isolating. Dr. Anthony Fauci said in a White House press briefing Wednesday that this person had been vaccinated, but when asked if they'd had a booster shot, he said "To my knowledge, no." [Update: It's been confirmed that the patient had two doses of the Moderna vaccine, but had not had any booster.]

It's been confirmed that the patient is a San Francisco resident. The person's known contacts have reportedly all been informed of their possible exposure, and have been tested, apparently all testing negative so far.

Per CNN, Fauci also said the patient's symptoms were already "improving at this point." SF's Director of Public Health Dr. Grant Colfax suggested in a Wednesday news conference that the person had already mostly recovered.

The existence of the variant has only been widely acknowledged since Friday, the 26th, and this case only further proves that Omicron had likely been circulating for weeks before South African officials and the W.H.O. raised alarm bells last week.

It remains unclear if the Omicron variant is much more highly transmissible than the Delta variant, or if it leads to any more severe level of infection — at this point, scientists have labeled it a "variant of concern" simply because of its constellation of mutations, and not any public health data. The majority of cases found so far in South Africa have been among young people, leading experts to caution that any data about infection severity is likely to be skewed before we have a broader sample.

The San Francisco Department of Public Health posted a tweet Monday saying, "The omicron variant is concerning but, as of now, we believe our vaccines and treatments are effective against it."

The CDC, after it already was aware of this Omicron case in San Francisco, announced Tuesday that it would be stepping up surveillance efforts at four U.S. airports including SFO in an effort to find newly arriving cases from abroad.

Also on Tuesday, CDC Director Rochelle Walensky defended the agency's overall surveillance efforts, saying that it recent months it had stepped up those efforts and was now running genetic sequencing on one out every seven positive COVID cases in the country.

"We are actively putting systems in place with local and state laboratories to make detection and sequencing even faster," Walensky said, per NPR.

Related: Swift Sequencing of Omicron Sample at UCSF Highlights Challenges of Tracking Variant's Spread

Top image: Dr. Fauci at the White House briefing on December 1, 2021. Photo by Anna Moneymaker/Getty Images

This post has been updated throughout.