The Covid-19 virus is spreading faster than ever in South Africa, the country’s president said Monday, an indication of how the new Omicron variant is driving the pandemic, but there are early indications that Omicron may cause less serious illness than other forms of the virus.

Researchers at a major hospital complex in Pretoria reported that their patients with the coronavirus are much less sick than those they have treated before, and that other hospitals are seeing the same trends. In fact, they said, most of their infected patients were admitted for other reasons and have no COVID symptoms.

But scientists cautioned against placing too much stock in either the potential good news of less severity, or bad news like early evidence that prior coronavirus infection offers little immunity to Omicron. The variant was discovered just last month, and more study is needed before experts can say much about it with confidence. Beyond that, the true impact of the coronavirus is not always felt immediately, with hospitalizations and deaths often lagging considerably behind initial outbreaks.

Dr. Emily S. Gurley, an epidemiologist at Johns Hopkins Bloomberg School of Public Health, said of the signs that the variant is less severe, “It would not be shocking if that’s true, but I’m not sure we can conclude that yet.”

In the absence of more hard information, governments have reacted to Omicron with sharp restrictions on international travel and new vaccination requirements. World leaders who were accused of responding too slowly or weakly earlier in the pandemic are eager to be seen as taking action, though some experts question whether the travel restrictions are an overreaction. 

The variant has spread rapidly and has been detected in more than 30 countries on six continents so far. Health officials and researchers say that it could be the most contagious form of the virus yet, and that it could soon displace the Delta variant that emerged last year as the predominant form. That has fueled fears that a world eager to emerge from two years of pandemic hardship could be headed into another cycle of illness, lockdown and economic suffering.

In Europe, as in South Africa, there are early indications that Omicron cases may be fairly mild, if easy to contract.

In Britain, the government said Monday that the number of Omicron cases there had climbed to 336, two and a half times as many as on Friday. Denmark reported 261 cases, quadruple the number on Friday, and local media there have reported that a holiday lunch for high school students may have been a super-spreader event, with dozens of people catching the new variant.

Britain and Denmark do an unusually large amount of genomic sequencing of virus samples, to tell one variant from another and detect changes, which suggests that many Omicron cases in other countries are simply going undetected.