Despite the detection of Omicron, Delta remains the predominant strain in the United States.
LOS ANGELES, Dec. 2 (Xinhua) -- The United States has identified the country's first confirmed case of the Omicron COVID-19 variant in the state of California, health authorities said Wednesday.
The California and San Francisco Departments of Public Health have confirmed that a recent case of COVID-19 among an individual in California was caused by the Omicron variant. The individual was a traveler who returned from South Africa on Nov. 22, the U.S. Centers for Disease Control and Prevention (CDC) said in a news release.
Officials said that genomic sequencing was conducted at the University of California, San Francisco and the sequence was confirmed at CDC as being consistent with the Omicron variant.
The individual, who was fully vaccinated and had mild symptoms that are improving, is self-quarantining and has since tested positive. All close contacts have been contacted and have tested negative, according to the CDC.
The health agency said the emergence of the variant "emphasizes the importance of vaccination, boosters, and general prevention strategies needed to protect against COVID-19. Everyone 5 and older should get vaccinated. Boosters are recommended for everyone 18 years and older."
The CDC noted that public health officials have been actively monitoring and preparing for the new variant, and will continue to work diligently with other U.S. and global public health and industry partners to learn more.
Despite the detection of Omicron, Delta remains the predominant strain in the United States, said the agency.
The case was detected in someone who arrived in the United States from South Africa on Nov. 22 and tested positive for COVID-19 on Monday, said San Francisco health director Grant Colfax in a press briefing at City Hall on Wednesday.
That person, who had two shots of the Moderna vaccine, without a booster, developed mild symptoms three days after returning to San Francisco, he said.
"They did the right thing and got tested," Colfax added.
"We knew that it was only a matter of time until the Omicron variant was detected in our city, and the work that we have done to this point has prepared us to handle this variant," San Francisco Mayor London Breed said in a statement. "We continue to encourage everyone to get vaccinated, get boosted, and take steps to keep each other safe."
California Governor Gavin Newsom tweeted Wednesday that the western U.S. state's "large-scale testing and early detection systems have found the Omicron COVID-19 variant in California" and "we should assume that it's in other states as well."
"There's no reason to panic -- but we should remain vigilant. That means get vaccinated. Get boosted. Wear a mask indoors," he noted, adding that 92.1 percent of all Californians 18 and older have received at least one dose of the COVID-19 vaccine.
California, home to around 40 million residents, is the most populous U.S. state and once an epicenter of the COVID-19 pandemic in the country. The state has reported over 4.8 million confirmed COVID-19 cases and over 73,700 related deaths to date.
South Africa reported the variant to the World Health Organization last week, and the agency labeled Omicron a "variant of concern."
The U.S. government responded last Friday by announcing international travel restrictions for eight southern African countries.
U.S. President Joe Biden said Monday that the variant is "a cause for concern, not a cause for panic." The Biden administration is reportedly planning stricter testing requirements for all travelers entering the country.
Top officials are considering requiring everyone who enters the country to be tested for COVID-19 the day before their flight and having all travelers be tested again after returning home, regardless of vaccination status, CNN reported.