Western Africa is bracing against an unprecedented outbreak of the deadly ebola virus. Guinea is the country affected the worst by the viral hemorrhagic fever. Since January, 86 people have died from it, out of 137 cases.

Shutting down the body’s immune system, ebola is highly contagious, transmitted by contact with the fluids of infected people or animals.

Epidemiologist Michel Van Herp, in Guinea with the non-governmental organisation MSF (Doctors Without Borders) said: “We are facing a scale that has never been seen before, looking at the number of cases in different areas.”

Death tolls in the past have been higher than in Guinea so far, such as in the Democratic Republic of Congo in 2001 and Uganda the year before. But this time cases have been found far apart, not geographically concentrated. MSF describes ebola as one of the world’s deadliest diseases. There is no cure.

Van Herp said: “We are facing the most aggressive strain of ebola, the Zaire strain. It kills more than nine out of 10 people infected.”

Identified in 1976 in former Zaire, now the Democratic Republic of Congo, this is the first time ebola has struck in Guinea. It is also thought to have spread to Liberia, Sierra Leona and Mali.

The natural host of this virus is thought to be essentially bats and other animals. Health officials have told people not to eat wild meat. Infected humans can pass the virus on through sex and direct contact with blood, mucus and other bodily fluids.

Research Professor Jean-Jacques Muyembe says: “We think the big bats who eat fruit are the main carriers, but we still have to confirm this. The only way to fight ebola is by practising good hygiene and interrupting the train of transmission, meaning detect the disease rapidly — the people who are already infected — and isolate them.”

Ebola goes from sore throat to fever, muscle pain, headaches, vomiting, diarrhoea, organ failure and blood loss.

Death can take from days to weeks.