Canadian officials announced Sunday that the omicron variant of the coronavirus has reached North America, with two cases appearing in Ontario.
Top Ontario health officials Christine Elliott and Kieran Moore said in a joint statement that two people who had recently been in Nigeria have tested positive for the variant.
Contact tracing was being conducted to determine whether others in the country might be positive.
The health officials said their strategy is to stop as many omicron cases as possible from entering Canada.
"We continue to urge the federal government to take the necessary steps to mandate point-of-arrival testing for all travellers irrespective of where they’re coming from to further protect against the spread of this new variant," the pair said.
Ontario has focused rapid COVID-19 testing on travelers who have been to South Africa, Botswana, Lesotho, Eswatini, Mozambique, Namibia and Zimbabwe, the statement said.
Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, said Saturday on Weekend TODAY that the variant could already be in the U.S.
"We have not detected it yet, but when you have a virus that is showing this degree of transmissibility and you’re already having travel-related cases that they’ve been noted in Israel and Belgium and in other places — when you have a virus like this, it almost invariably is ultimately going to go essentially all over," he said.
Fauci explained why the variant has inspired global caution: Its apparent mutations indicate that it may be highly transmissible and able to escape the body’s immune response, as well as some protection rendered by vaccines.
"You don’t want to frighten the American public, but when something occurs that you need to take seriously, you take it seriously, and you do whatever you can to mitigate against that," he said.
Fauci, who met Sunday with President Joe Biden, said existing vaccines are likely to provide "a degree" of protection against severe cases of COVID-19, the White House said in a readout that paraphrased his remarks.
Fauci also reiterated that getting booster shots provides additional protection, the White House said.
Biden was expected to provide an update Monday about the U.S. response to the variant. Sunday afternoon’s readout did not mention the Ontario discovery.
The spread of the omicron variant prompted Israel to close its borders to travelers Saturday, with some exceptions.
This article was originally published on NBCNews.com.