Health officials in Guinea are monitoring 155 people they fear may have caught a deadly Ebola-like disease.
One man has already died from Marburg virus, prompting a desperate scramble to find everyone he came into contact with.
All of the people he met have now been traced and told to self-isolate. They are also being kept under observation for three weeks.
The case, detected last week in Gueckedou, marked the first time the virus has been spotted in West Africa.
No other cases have been detected yet — but the World Health Organization warned the affected village is near the country’s border with Sierra Leone and Liberia.
Marburg is one of the deadliest pathogens known to exist, killing between half and 90 per cent of everyone who gets infected.
The virus is carried by fruit bats but can be spread between humans through blood and bodily fluids, as well as touching contaminated surfaces.
Infected patients can resemble ghosts, with deep-set eyes and expressionless faces, according to the WHO. Other symptoms include headache, diarrhoea, stomach pain and vomiting.
After five days, many patients start to bleed under the skin, in internal organs or from openings such as the mouth, eyes and ears. Patients often die from nervous system failure, not blood loss.
Experts are now working to identify the source of the outbreak and searching for more possible contacts.
Dr Georges Ki-Zerbo, the WHO’s country head in Guinea, said Marburg had been circulating in animals, particularly bats, in southern Guinea and neighbouring Sierra Leone and Liberia.
Pathogens have tended to cross from animals to humans in the region because of their close interaction, notably in the hunting and eating of ‘bushmeat’ from the wild.
Dr Georges Ki-Zerbo said: ‘There is no known secondary case. The contacts have been traced, and 155 people are under observation for three weeks.
‘It is active surveillance. The contacts are kept at home, isolated from other members of the family. They are visited every day to check on potential symptoms.’
Marburg and Ebola are closely related.
Guinea was declared free of Ebola two months ago, following an outbreak that killed 12 people.
Dr Ki-Zerbo said Guinea was better prepared to handle an outbreak than it had been when Ebola struck in 2014. The discovery of the Marburg case also indicated improved ability to detect such infections.
He said Guinea has built a ‘robust health security system’ since the last Ebola outbreak, including the use of rapid response teams, disease detectives, epidemiologists and social anthropologists, and better coordination with neighbouring countries.
He added: ‘Globally, the approach to combating Marburg would not be different from Ebola.
‘The only difference is that there is no vaccine or drug specifically directed to the virus. Only supportive care is available.’