The United States joined Canada, the European Union and several other countries in instituting travel restrictions on visitors from southern Africa in a wave of international reactions to the a new, highly mutated coronavirus variant discovered by South African scientists.

A World Health Organization panel named the variant "omicron" and classified it as a highly transmissible virus of concern, the same category that includes the delta variant, the world's most prevalent. The panel said early evidence suggests an increased risk of reinfection.

The White House said the U.S. will restrict travel from South Africa and seven other countries in the region beginning Monday. It did not give details except to say the restrictions will not apply to returning U.S. citizens or permanent residents, who will continue to be required to test negative before travel. Meanwhile, Canada banned entry of foreign nationals who have traveled through southern Africa.

The European Union had earlier issued an order suspending travel from South Africa and surrounding nations after alarm about the new variant was sounded by scientists and world leaders.

"All air travel to these countries should be suspended," European Commission President Ursula von der Leyen said. "And they should be suspended until we have a clear understanding about the danger posed by this new variant. And travelers returning from these regions should respect quarantine rules."