The World Health Organization (WHO) on Friday classified the new B.1.1.529 coronavirus variant as a "variant of concern" and gave it the name "omicron."
The WHO held an urgent meeting in Geneva over the risks posed by the omicron variant, first discovered in South Africa.
It said the omicron variant appears to come with an increased risk of reinfection and likely has a growth advantage over other variants.
The working committee asked countries to increase surveillance and sequencing efforts and to report findings, and called on people to stay vigilant against the virus.
"Once a variant is classified as a variant of concern, it's really important that we have good SARS-COV2 surveillance around the world, including better genomic sequencing because we want to be able to detect this variant where it is circulating," the group said.
"This variant has a large number of mutations and some of these mutations have worrying characteristics," it added.
Widely used PCR tests still appear to be able to detect omicron, meaning current diagnostics should work.
The variant has caused stock markets to plummet and led to a suspension of flights from southern African countries.
However, WHO spokesperson Christian Lindmeier urged countries against quickly imposing travel restrictions, saying officials should take a "risk-based and scientific approach."
"At this point, implementing travel measures is being cautioned against," Lindmeier said.
Concerns that this variant will 'evade' vaccines
The WHO stressed that scientists are rushing to gain more information about the variant. In particular, health authorities are seeking to determine if the currently available vaccines are effective against omicron.
Ahead of the meeting, the WHO's special envoy on COVID-19, David Nabarro, told the BBC that, in his view, "it is appropriate to be concerned" about the new variant spreading in southern Africa.
"I'll tell you why — the virus looks like it will have greater capacity to evade the defenses that we've all built up as a result of the vaccinations we've received since the beginning of this year," he said.
What do we know about the variant?
South Africa's National Institute for Communicable Diseases (NICD) confirmed there were 22 confirmed cases of the omicron variant in the country.
Fewer than 100 full genome sequences of the variant are so far available, according to the WHO's COVID-19 technical lead, Maria Van Kerkhove.
"Everybody that's out there needs to understand that the more this virus circulates, the more opportunities the virus has to change, the more mutations we will see," she said.
Currently only 6.6% of people on the African continent have been fully vaccinated. However, fears are also growing in areas with much higher vaccination rate.
How has travel been affected?
Countries across the globe have reacted to the new variant by shutting down travel from southern Africa.
Germany, the United States, the United Kingdom, Israel and Italy are among a number of countries that have suspended travel to the region, but South Africa believes they have acted too hastily.
Nevertheless, South African President Cyril Ramaphosa will convene the National Coronavirus Command Council on Sunday, a government statement said. Decisions taken by the council shape the government's stance on the pandemic.
In September, South Africa began easing lockdown restrictions, despite low vaccination rates.
jsi,jcg/aw (Reuters, AP, dpa, AFP)
Correction, November 27, 2021: A previous version of this article misidentified the WHO's COVID-19 technical lead. DW apologizes for the error