Taking a PCR Covid test before the opening ceremony of the Africa Cup of Nations at the Olembe Stadium in Yaounde, Cameroon, in January.Credit...Mohamed Abd El Ghany/Reuters

A W.H.O.-led analysis published last month and not yet peer-reviewed synthesized 150 surveys across the continent and found that 65 percent of Africans had been infected with the coronavirus as of September, nearly 100 times the number of confirmed cases.

“Available data is likely only scratching the surface of the real extent of coronavirus infections in Africa,” the official, Dr. Matshidiso Moeti, said at a news conference on Thursday.

Infections have been underreported across the world, but the new analysis suggests Africa has among the highest rates of infection. Dr. Moeti said that antibody levels varied in populations across the continent, with the highest levels in eastern, western and central African countries.

Experts have been divided on the reasons behind Africa’s low levels of reported Covid deaths and severe illness, despite studies now showing that the virus has circulated widely across the continent. With just over 15 percent of the population in Africa fully vaccinated, antibodies overwhelmingly come from infections.

But Africa is young: 42 percent of the population is under 15, and just 3 percent 65 or older. And the conditions that make Covid-19 more lethal, such as obesity, diabetes and hypertension, are less common.

“Should we be panicking and worrying? No, this is exposure to a virus,” Dr. Moeti said. “We’ve seen that it has produced some illness and some deaths, but not a devastating situation.”

Dr. Moeti added that such levels of exposure had conferred high levels of immunity. “That is a contribution to preventing the spread of the virus, although the immunity is not prolonged,” she said.

As of Wednesday, the W.H.O. said, the confirmed death toll in Africa was 252,000.

Most African countries have now dropped virus restrictions, including mask mandates, and nearly half no longer require quarantine after exposure.

On Monday, South Africa lifted its “state of disaster” for the first time, and last month Ghana reopened its land and sea borders in a move that had been long awaited by countless Ghanaians who depend on trade with neighboring Ivory Coast, Burkina Faso and Togo. Private parties, religious gatherings and movie theaters also returned to full capacity for vaccinated people in the West African nation of 31 million.

But as countries lower their guard, Dr. Moeti warned that Africa wasn’t immune to the risks of more lethal variants overwhelming immunity.

Last month, the W.H.O. warned that 22 African countries were no longer carrying out any kind of contact tracing. “This, along with robust testing, is the backbone of any pandemic response,” Dr. Moeti said.