The World Health Organization said at least four people have turned up as contacts of a man who died from the Ebola-like Marburg virus in Guinea, as staffers from the UN health agency were deployed to the West African country to help authorities prevent an outbreak.

WHO spokeswoman Fadela Chaib said the case, reported late on Monday, amounts to the first in West Africa – in a region that was swept up by a devastating Ebola outbreak between 2014 and 2016 that killed at least 11,325 people.

Chaib said authorities were working to trace contacts of the man, who had visited a health facility before he died.

“At least four people he came in contact with are asymptomatic. So they did not show the disease,” she said.

She also said 10 staff of the WHO were conducting contact tracing in Guinea.

The Marburg virus belongs to the same family as Ebola, and previously outbreaks have erupted elsewhere across Africa in Angola, Congo, Kenya, South Africa and Uganda.

Marburg symptoms include high fever and muscle pains, and some patients later bleed through body openings like eyes and ears.

There is no approved drug or vaccine for Marburg, but rehydration and other supportive care can improve a patient’s chances of survival.

Case fatality rates have been as high as 88% in previous outbreaks, but WHO said the figure has varied, based upon the strain and how cases were managed.