Ebola, believed to be caused by four or five viruses, begins with influenza-like symptoms. Headaches, confusion, seizures and sometimes coma can follow, as well as a rash. For a large proportion of those affected the disease is fatal, due to multiple organ failure.
A candidate Ebola vaccine has been tested in mice but it appears an approved human vaccine is still a long way off.
The latest outbreak covers a large geographical area and the WHO describes the latest outbreak as “one of the most challenging” it has seen.
Guinea is reporting 157 cases, of which 101 have been fatal. Neighbouring Liberia has recorded 21 suspected cases with seven deaths, and Mali is also thought to have a small number of cases, according to media reports.
Rumours of cures are circulating, including claims that hot chocolate, coffee and raw onions taken once a day for three days will kill the virus, but none of this has ever been shown to help.
There was concern that a man in Canada who had recently arrived from Liberia, had unwittingly brought the disease to North America. However, those fears have eased after tests showed he was not carrying Ebola viruses.
The European Centre for Disease Prevention & Control (ECDC) is monitoring the situation. It warns that new cases are expected to be identified in the coming weeks but says tourists and visitors are at low risk of infection if simple precautions are taken.
The ECDC recommends avoiding contact with symptomatic patients, corpses, wild animals, the consumptions of ‘bushmeat’ and advises people in the region to practise hygienic food preparation and safe sex.
People providing medical care in the outbreak area are advised to wear protecting clothing including masks, gloves, gowns and eye protection.
Efforts to track the outbreak were hampered by the lack of information available to health workers. In particular, there were effectively no maps. This prompted aid agencies to recruit an army of online volunteers to help build maps from scratch based on satellite imagery.
To start with, Médecins Sans Frontières (MSF) asked a Humanitarian OpenStreetMap Team (HOT) to build them a map of Guéckédou, a city of around 250,000 people in southern Guinea, where the outbreak is concentrated.
Around 200 volunteers from around the world built a digital map with 100,000 buildings based on satellite imagery of the city. In less than 20 hours, they had mapped three cities, according to cartONG, a mapping NGO that is working with MSF to coordinate the project.
While international agencies are beginning to get to grips with the scale of the outbreak, they say it will be several months before it abates.