A sign promotes a COVID-19 testing location located inside the Tom Bradley International Terminal at Los Angeles International Airport (LAX) on December 01, 2021. (Photo by AFP)

The United States says it has detected the first case of the Omicron variant of the coronavirus in California, as fear and uncertainty keep spreading over the new concerning strain across the globe.

The patient, a resident of San Francisco who was fully vaccinated, has recently returned from South Africa, the Centers for Disease Control and Prevention (CDC) said in a statement on Wednesday.

The person is in isolation, the agency said, and aggressive contact tracing is underway.

It said that the individual is self-quarantining and close contacts have tested negative for the disease so far.

The discovery triggered fears across the nation over the impact of the Omicron variant, which was first reported in South Africa last month and has since spread to at least two dozen countries.

The World Health Organization (WHO) designates Omicron a variant of concern, warning that the new strain poses a very high global risk.

The White House plans to announce stricter testing rules for international visitors.

Airlines in the US were ordered to disclose passenger names and other information about those who have recently been in eight southern African countries, according to documents seen by Reuters.

Chief White House medical adviser Anthony Fauci urged Americans to get vaccinated against COVID-19.

We know what we need to do to protect people, Fauci said shortly after the first case reported on Wednesday.

The fact is that people should wind up getting vaccinated and boosted if they’re eligible for a boost. I keep coming back to that because that’s really the solution to this problem, Fauci said.

According to South Africa’s National Institute for Communicable Diseases (NICD), early epidemiological data suggested Omicron was able to evade some immunity, but existing vaccines should still protect against severe disease and death.

President Joe Biden also called the variant a cause for concern, not a cause for panic. He said on Monday that the US has to face this new threat just as we face those who have come before it.

Omicron keeps spreading across the world while the other variant, Delta still remains the dominant variant globally and in the United States.