JOHANNESBURG (AP) — Driven by the delta variant, a new wave of COVID-19 is sweeping across the African continent where new cases, hospital admissions, and deaths are increasing.

South Africa is leading the new surge in Africa, where case numbers are doubling every three weeks, according to the World Health Organization.

“The speed and scale of Africa’s third wave is like nothing we’ve seen before," said Dr. Matshidiso Moeti, WHO's regional director for Africa.

The delta variant, reported in 16 African countries, has become dominant in South Africa, which accounts for more than half of Africa’s new cases. It was detected in 97% of samples sequenced in Uganda and in 79% of samples sequenced in Congo, said WHO.

“The rampant spread of more contagious variants pushes the threat to Africa up to a whole new level,” Moeti said in a statement. "More transmission means more serious illness and more deaths, so everyone must act now and boost prevention measures to stop an emergency becoming a tragedy.”

Less than 2% of Africa’s 1.3 billion people have received even one dose of a vaccine.

With more than 20,000 new cases reported Friday, South Africa's total of 1.9 million cases, including 66,323 deaths, represents more than 30% of the 5.5 million cases reported by Africa's 54 countries, representing 1.3 billion people, according to the Africa Centers for Disease Control and Prevention.

Johannesburg and the surrounding Gauteng province are South Africa's epicenter with its hospitals reaching 91% capacity and 5,500 additional health workers deployed, the health department announced Friday.

Staff at Tshepong Hospital in Klerksdorp, about 170 kilometers (105 miles) southwest of Johannesburg, say they are battling to cope with the new surge.

“With this new strain in the third wave, I think it’s more aggressive than the second one," Onthatile Mmusi, a nurse at Tshepong Hospital said. “We tend to get patients and when they come in their oxygen levels are already down.”