Around the same time, researchers in South Africa stumbled across Omicron in a cluster of cases in the province of Gauteng. As of Friday, they have listed 58 Omicron samples on the variant database. But at a news conference on Thursday, Tulio de Oliveira, the director of the Centre for Epidemic Response & Innovation in South Africa, said that “close to two or three hundred” genetic sequences of Omicron cases would be released in the next few days.
The W.H.O. called for increased surveillance of the variant and laboratory experiments to better understand its biology.
“This variant did surprise us,” Dr. de Oliveira said at the news conference. “But the full significance is still uncertain.”
Dr. de Oliveira and his colleagues asked the W.H.O. to hold an emergency meeting about the variant on Friday for two reasons: the mutations in Omicron and what appears to be an alarming spread in South Africa.
The researchers found more than 30 mutations on a protein, called spike, on the surface of the coronavirus. The spike protein is the chief target of antibodies that the immune system produces to fight a Covid-19 infection. So many mutations raised concerns that Omicron’s spike might be able to evade antibodies produced by either a previous infection or a vaccine.
Dr. de Oliveira and his colleagues determined a quick way to gauge how quickly Omicron was spreading in South Africa. Although sequencing the entire genome of a virus is slow, the scientists figured out how to identify Omicron with a standard nasal swab test known as P.C.R.
The tests are fast because they look for just two of the coronavirus’s 29 genes — the spike gene and another gene called nucleocapsid. Thanks to its new mutations, Omicron does not test positive for the spike gene. So researchers could simply look for samples that tested positive for nucleocapsid, but negative for spike.