South African health officials are performing tests for Marburg virus infection on a sick passenger who arrived on a plane from Angola, which is battling the worst ever outbreak of the lethal virus, officials said on Wednesday.

The passenger was taken to hospital for tests after arriving late on Tuesday from Angola’s capital Luanda, South African Airways (SAA) spokesman JJ Tabane said.

“We are still waiting for the results,” Tabane told Reuters.

Marburg, a haemorrhagic fever related to Ebola, has killed 237 people in Angola. Most have died in the province of Uige, although a few cases have been recorded in other areas, including Luanda, among people who have travelled from Uige.

Tabane said the other passengers on the plane from Luanda were allowed to continue their journeys after arrival in Johannesburg.

“This was nothing to do with the other passengers, who arrived normally and went home to their families,” he said.

But the plane was taken out of service to be disinfected, Tabane added. “The airport health authorities are on top of this,” he said.

Marburg is named after the German town where the disease was first recorded among scientific researchers who contracted it in the 1960s from monkeys imported from Africa.

The disease, which has killed more than 90 percent of people known to be infected in the Angolan outbreak, causes severe headaches, muscle pain, vomiting, diarrhoea and internal bleeding. Death normally occurs eight or nine days after symptoms start, preceded by severe blood loss and shock.

There is no cure.