Nations around the world are beginning to close their borders over concern about a new variant of COVID-19 called Omicron that has emerged from Southern Africa.
The World Health Organization calls Omicron "a variant of concern," but admits more needs to be learned about it.
Initial reports describe it as having very mild symptoms.
But the virus may also be highly transmissible. Two new cases have just been confirmed in Canada, the first known to have reached North America.
Dr. Ashish Jha, dean of Brown University's School of Public Health, said preliminary evidence shows that it is more transmissible. "We don't know for sure. We really have no data on severity, whether it's more severe, milder, or more significant," Jha said.
The United States has decided to ban travelers from South Africa and seven other countries in the region.
Israel has closed its borders to noncitizens for two weeks and has authorized cell phone surveillance of anyone confirmed to be carrying the variant.
Japan also suspended entry to foreign visitors.
But the head of the South African Medical Association, Dr. Angelique Coetzee, said Western nations are panicking unnecessarily.
"There's body aches and pain with a bit of a headache, not really sore throat, more of a scratchy type of description and no cough and no loss of smell or taste. And that's what I call 'mild symptoms.'"
South Africa's Health Minister, Joe Phaala, slammed what he called the 'draconian' travel bans.
"The reaction of some of the countries in terms of imposing travel bans and such measures are completely against the norms and standards as guided by the World Health Organization."
WHO has called for international borders to remain open.
Former FDA Commissioner and Pfizer Board member Dr. Scott Gottlieb told CBS that yes, Omicron seems to be highly transmissible, but world leaders shouldn't have panicked and their actions may discourage other nations from reporting new variants.
"It has a lot of mutations that correlate with escape from immunity that is conferred by prior infection or by the vaccine. But we didn't need to close off travel and unfortunately, we're punishing South Africa for doing the right thing," Gottlieb said.
Health officials say more data is needed to determine if vaccines are effective against the Omicron variant. It's most likely already in the United States, although so far, no cases have been reported. Joe Biden delivered remarks on Monday about the new strain, saying, “This variant is a cause for concern, not a cause for panic."