Passengers wait in a line to receive quarantine test on their arrivals at Kansai International Airport in Osaka, western Japan, Tuesday, Nov. 30, 2021. Japan confirmed on Tuesday its first case of the new omicron coronavirus variant, a visitor who recently arrived from Namibia, an official said.Credit: Yukie Nishizawa/Kyodo News via AP

Japan and France confirmed their first cases of the new variant of the coronavirus on Tuesday as countries around the world scrambled to close their doors or find ways to limit its spread while scientists study how damaging it might be.

The World Health Organization has warned that the global risk from the omicron variant is "very high" based on early evidence, saying it could lead to surges with "severe consequences."

French authorities on Tuesday confirmed the first case of the omicron variant in the French island territory of Reunion in the Indian Ocean. Patrick Mavingui, a microbiologist at the island's research clinic for infectious diseases, said the person who has tested positive for the new variant is a 53-year-old man who had traveled to Mozambique and stopped in South Africa before returning to Reunion.

The man was placed in quarantine. He has "muscle pain and fatigue," Mavingui said, according to public television Reunion 1ere.

Japan on Tuesday confirmed its first case in a visitor who recently arrived from Namibia, a day after banning all foreign visitors as an emergency precaution against the variant. A government spokesperson said the patient, a man in his 30s, tested positive upon arrival at Narita airport on Sunday and was isolated and is being treated at a hospital.

  • A worker lowers his mask as he sets up decorations ahead of year end festivities at a bar in Beijing, China, Tuesday, Nov. 30, 2021. The World Health Organization warned Monday that the global risk from the omicron variant is "very high" based on the early evidence, saying the mutated coronavirus could lead to surges with "severe consequences." Credit: AP Photo/Ng Han Guan

  • A woman wearing a face mask to protect against coronavirus poses with a friend for a selfie at Sacre-Coeur Basilica in Paris, Monday Nov. 29, 2021. The new potentially more contagious omicron variant of the coronavirus popped up in more European countries on Saturday, just days after being identified in South Africa, leaving governments around the world scrambling to stop the spread. Credit: AP Photo/Rafael Yaghobzadeh

  • A currency trader passes by screens showing the Korea Composite Stock Price Index (KOSPI) and the foreign exchange rate between U.S. dollar and South Korean won, right, at the foreign exchange dealing room of the KEB Hana Bank headquarters in Seoul, South Korea, Tuesday, Nov. 30, 2021. Asian shares were mixed Tuesday as investors continued to cautiously weigh how much damage the new omicron coronavirus variant may unleash on the global economy. Credit: AP Photo/Ahn Young-joon

  • A person is tested for COVID-19 in Abuja, Nigeria, Monday Nov. 29, 2021. Countries around the world slammed their doors shut again to try to keep the new omicron variant at bay Monday, even as more cases of the mutant coronavirus emerged and scientists raced to figure out just how dangerous it might be. Credit: AP Photo/Gbemiga Olamikan

Cambodia barred entry to travelers from 10 African countries, citing the threat from the omicron variant. The move came just two weeks after Cambodia reopened its borders to fully vaccinated travelers on Nov. 15.

The new version was first identified days ago by researchers in South Africa.

WHO said there are "considerable uncertainties" about the omicron variant. But it said preliminary evidence raises the possibility that the variant has mutations that could help it both evade an immune-system response and boost its ability to spread from one person to another.

The WHO stressed that while scientists are hunting evidence to better understand this variant, countries should accelerate vaccinations as quickly as possible.

Despite the global worry, doctors in South Africa are reporting patients are suffering mostly mild symptoms so far. But they warn that it is early. Also, most of the new cases are in people in their 20s and 30s, who generally do not get as sick from COVID-19 as older patients.