Tim Clark says Emirates is working on the basis the newly discovered variant can be dealt with effectively by vaccines, but acknowledges the next few weeks will prove critical for the industry as scientists assess the risks.

"I would say probably by the end of December, we'll have a much clearer position," Clark said on Tuesday.

"But in that time, December is a very important month for the air travel business," he added.

"If that is lost, or the winter is lost to a lot of carriers, there will be significant traumas in the business, certainly the aviation business and the periphery."

The World Health Organisation warned on Monday the heavily mutated Omicron coronavirus variant is likely to spread internationally and poses a very high risk of infection surges that could have "severe consequences" in some places.

Omicron was first reported on November 24 in southern Africa, where infections have risen steeply.

It has since spread to more than a dozen countries, many of which have imposed travel restrictions to try to seal themselves off.

Japan on Monday joined Israel in saying it would close its borders completely to foreigners.

"It's likely to arrest, inhibit, but not stall the uptick in demand that we've all had the benefit of in the last month or two," Clark said of Omicron.

He noted, however, that it could also "go the other way", with more draconian measures in response to a greater threat from the variant.

Clark said the airline's decision to close down flights out of South Africa and a handful of surrounding countries was difficult, given strong demand for the December period.

However, he said bookings generally remained strong despite the reintroduction of measures in some European markets such as track and trace, quarantine and PCR testing.

"People haven't made that decision to cancel or pull off, so we're hoping that it doesn't worsen, that the border procedures for re-entry are not so draconian that it prevents them from travelling at all," he said.

Australian Associated Press