CAPE TOWN, South Africa — South Africa’s new daily coronavirus cases have almost tripled in three days, according to new figures released Thursday, raising alarms over the possible spread of the new omicron variant recently detected by the country’s scientists.

New daily confirmed cases rose to 11,535 on Thursday from 8,561 on Wednesday and 4,373 the previous day, according to official statistics. The cases represent a 22.4 percent positivity rate of people tested for the virus, up from 16.5 percent on Wednesday, a massive jump from a 1 percent positivity rate in early November, the National Institute for Communicable Diseases said.

The majority of new infections were in the populous Gauteng province around the greater Johannesburg metropolitan area, with 8,280 cases, the NICD said.

“Omicron is probably the fastest-spreading variant that South Africa has ever seen,” said Tulio de Oliveira, director of the Center for Epidemic Response and Innovation at Stellenbosch University, reacting to news of the increase in cases.

Although scientists are warning that it is still too early to say for sure that omicron is behind the surge in cases, the rapid rise means omicron might already be overtaking the delta variant, experts said.

The delta variant was dominant in all provinces until the end of October, but the NICD said Wednesday that omicron was present in 74 percent of the genomes it sequenced in November.

Shabir Madhi, a professor of vaccinology at the University of the Witwatersrand in Johannesburg, said all indications were that omicron could be more transmissible than delta.

“The majority of cases are currently presenting as a mild illness,” he said, adding that most patients had a dry cough, fever and night sweats.

Delta drove the third coronavirus wave in South Africa, which peaked at more than 26,000 cases a day in early July. Omicron is expected to trigger a fourth wave, which some experts say may already be underway.

Hospitalizations are also rising but not yet at the same pace as new cases, Madhi said.

The sharp increase in the positivity rate was concerning and showed “a substantial amount of virus transmission taking place,” he added.

At the current rate of infection, South Africa could see infections rising to roughly 30,000 to 40,000 a day, he added.

Officials in Gauteng province said they were preparing for the worst ahead of the holidays. “We are not panicking, but we are deeply concerned,” Gauteng Premier David Makhura said Thursday.

Omicron has raised global concerns of a surge in infections, prompting governments around the world to impose travel restrictions against countries in southern Africa. While South African scientists have been praised globally for bringing the new variant to the attention of the world, the country’s political leaders say it is being unfairly punished for being transparent about its findings.

President Biden delivered remarks on the threat posed by the omicron coronavirus variant on Nov. 29, encouraging Americans to get vaccinated. (The Washington Post)

As infections rise across the country, South African health authorities made a fresh push this week to get more people vaccinated, setting up pop-up sites in shopping centers and at taxi stands. Just 36 percent of South Africa’s adult population is vaccinated, according to the Department of Health, raising concerns that more variants could emerge without more aggressive measures.

South Africa is also considering mandatory vaccinations and has created a task force to explore the issue, President Cyril Ramaphosa said earlier this week. But the government is hoping the threat from the omicron variant will encourage people to get vaccinated. Vaccine hesitancy, driven by fear and apathy, has been blamed for a slowdown in South Africa’s vaccination campaign.

As South Africa rushes to solve crucial questions over the next few weeks about omicron, de Oliveira and his colleagues have warned that the country could face a shortage of reagents — used in PCR tests to detect coronavirus and other viral infections — because of the travel ban.

Reagents are imported from Europe and the United States.

Anne von Gottberg, a microbiologist at the NICD, said Thursday that the restrictions mean there are fewer ways for supplies to enter the country. “There are fewer flights to choose from to bring in reagents, to bring in equipment, in addition to sending out specimens and isolates for people to be able to then work with Omicron,” Reuters reported she said.

World Health Organization epidemiologist Maria van Kerkhove said at a news conference Wednesday that fewer flights to the region were hampering shipments of research samples from South Africa.

“The travel bans that have been imposed … have caused some challenges for those samples to actually ship out of the country,” she said. “We’re finding a way to be able to share those materials so studies can be done.”