An aid organisation has described the outbreak of Ebola in Guinea as an "unprecedented epidemic" with a "worrisome" geographical spread.
Medecins Sans Frontiers (MSF) said on Monday that the Zaire strain of the Ebola virus was the most aggressive and deadly, killing more than 90 percent of patients.
"We are facing an epidemic of a magnitude never before seen in terms of the distribution of cases in the country: Gueckedou, Macenta Kissidougou, Nzerekore, and now Conakry," said Mariano Lugli, who is coordinating MSF's project in the Guinean capital of Conakry.
"MSF has intervened in almost all reported Ebola outbreaks in recent years, but they were much more geographically contained and involved more remote locations. This geographical spread is worrisome because it will greatly complicate the tasks of the organisations working to control the epidemic," said Lugli.
To date, Guinean health authorities have recorded 122 suspected patients and 78 deaths. Other cases, suspected or diagnosed, have been found in Sierra Leone and Liberia.
On Saturday, Senegal said its border crossings to Guinea would be closed "until further notice".
No treatment or vaccine is available for Ebola, a highly infectious and virulent disease which can cause uncontrollable bleeding.
The Zaire strain was first recorded 38 years ago in what is now the Democratic Republic of Congo.
It can be transmitted to humans from wild animals, and between humans through direct contact with blood, bodily fluids or the unprotected handling of contaminated corpses.
It kills faster than it spreads.