South Africa's rapid increase in COVID-19 cases attributed to the new omicron variant is resulting in mostly mild symptoms, doctors say.

“We've seen a sharp increase in cases for the past 10 days. So far they have mostly been very mild cases, with patients having flu-like symptoms, dry coughs, fever, night sweats, a lot of body pains," said Dr. Unben Pillay, a general practitioner in Gauteng province where 81% of the new cases have been reported.

“Most of these patients have been treated at home,” Pillay told an online press briefing Monday. “Vaccinated people tend to do much better. We have not seen a vast increase in hospitalizations, but this is still early days. Hospitalizations often come several days after a rise in confirmed cases.”

Most of the new cases in South Africa have been among people in their 20s and 30s, and doctors note that age group generally has milder symptoms of COVID-19 in any case. They warn that older people infected by the new variant could have more severe symptoms.

Learning more about the omicron variant is important as nations around the world sought Monday to keep the new variant at bay with travel bans and further restrictions, even as it remains unclear what the variant means for the COVID-19 pandemic.

Japan announced it would suspend entry for all foreign visitors, while new cases of the variant identified days ago by researchers in southern Africa appeared as far away as Hong Kong, Australia and Portugal. Portuguese authorities were investigating whether some infections there could be among the first reported cases of local transmission of the variant outside of southern Africa.

South Africa has seen its seven-day average of new cases over the past two weeks surge from about 200 per day to more than 2,000.

Omicron appears to be more transmissible than previous variants and the surge in South Africa could bring the daily number of new cases to 10,000 by the end of the week, infectious diseases specialist Salim Abdool Karim, told the briefing.

“Our biggest challenge will be to stop super-spreading events, particularly indoors,” he said, suggesting that it might be necessary to restrict indoor gatherings to those who are vaccinated.

The hotspot for the new surge is Gauteng's Tshwane metropolitan area, incorporating the capital, Pretoria. The “vast majority” of those hospitalized there have been unvaccinated people, said Waasila Jassat of the National Institute for Communicable Diseases.

“Of recent hospitalizations 87% have been unvaccinated, 13% have been vaccinated,” Jassat said of the 455 hospital admissions in the Tshwane area in the past two weeks.

Vaccination appears to have also helped people avoid infection, she said.

Of South Africa's 60 million people, 16.5 million are vaccinated and the number of fully vaccinated who are testing positive is very small, said Nicholas Crisp, the acting director general of the department of health. "It is a very small number of those people who tested positive. It’s minute in comparison to unvaccinated people.”

To combat the surge of COVID-19 cases attributed to the omicron variant, South Africa is urging vaccinations and is weighing making vaccines mandatory to enter indoor areas, the minister of health said Monday.

The government is not planning to impose centralized vaccine mandates, but will support businesses and organizations that seek proof of vaccination to enter indoor areas, Minister of Health Joe Phaahla told reporters.

The government is considering requiring vaccines for health workers, including those who work at state hospitals, he said.

“We are looking at concrete proposals on how to deal with vaccine mandates in workplaces and health care workplaces,” Phaahla said.

A few African countries, including Angola, Egypt, Mauritius and Rwanda, have joined the slew of nations that have placed travel restrictions on South Africa and other countries in southern Africa.

“It’s quite regrettable, very unfortunate and I’ll even say sad to be talking about travel restrictions imposed by a fellow African country,” said Clayson Monyela, spokesman for the Department of International Affairs and Cooperation. He called the decisions “unwarranted and unjustified because it’s not based on science,”