The first documented case in the United States is a fully vaccinated Californian who returned from South Africa on November 22 and tested positive seven days later.
Dr. Anthony Fauci, the top US infectious disease officer, told reporters at the White House that the person had minor symptoms and was in self-quarantine.
During a White House coronavirus briefing, Rochelle P. Walensky, director of the Centers for Disease Control and Prevention, noted that as part of the intensified efforts to fend off novel variants, the US has expanded genome sequencing to 80,000 samples per week, more than any other country.
Meanwhile, the number of new cases reported in South Africa doubled from Tuesday to Wednesday.
Britain and the United States have both expanded their booster programs in response to the new variant.
The WHO has noted many times that the coronavirus will keep producing new variants for as long as it is allowed to circulate freely in large unvaccinated populations.
Some 56 countries were reportedly implementing travel measures to guard against Omicron as of Nov. 28, the WHO said.
U.N. Secretary-General Antonio Guterres slammed what he called “travel apartheid.”
“Blanket travel bans will not prevent the international spread and they place a heavy burden on lives and livelihoods,” the WHO said, while advising those who were unwell, at risk, or 60 years and over and unvaccinated to postpone travel.
The United States has barred nearly all foreigners who have been in one of eight southern African countries.