Guinea's government raised the death toll in the Ebola epidemic raging through its southern forests to 59.
The health ministry told the AFP news agency workers battling to contain the outbreak in the border region had added a further 25 deaths to the toll of 34 given earlier on Saturday, with a total of 80 cases registered.
"The Ebola fever epidemic raging in southern Guinea, including the prefectures of Gueckedou and Macenta, since February 9 has left at least 59 dead out of 80 cases identified by our services on the ground," said Sakoba Keita, the ministry's chief disease prevention officer.
"We are overwhelmed in the field, we are fighting against this epidemic with all the means we have at our disposal with the help of our partners but it is difficult. But we will get there," he told AFP.
To date, no treatment or vaccine is available for Ebola, which kills between 25 and 90 percent of those who fall sick, depending on the strain of the virus, according to the World Health Organisation.
The disease is transmitted by direct contact with blood, faeces or sweat, or by sexual contact or unprotected handling of contaminated corpses.
Medical aid group Doctors Without Borders (MSF) said in a statement it would strengthen its team of 24 doctors, nurses, logisticians and experts in hygiene and sanitation already in Guinea.
The organisation has set up isolation units for suspected cases in the southern region of Nzerekore and is looking for people who may have had contact with the infected.
"These structures are essential to prevent the spread of the disease, which is highly contagious," said MSF tropical medicine adviser Esther Sterk said.
"Specialised staff are providing care to patients showing signs of infection."
MSF said it was sending around 33 tonnes of medicines and isolation, sanitation and protective equipment in two planes leaving from Belgium and France.
Ebola, one of the world's most virulent diseases, was first discovered in the Democratic Republic of Congo (DRC) in 1976 and the country has had eight outbreaks.
The most recent epidemic, in the DRC, infected 62 people and left 34 dead between May and November 2012, according to the country's health ministry.
There are fears it could be used in a biological weapons attack.
According to researchers, the virus multiplies quickly, overwhelming the immune system's ability to fight the infection.
A medic in Monrovia told AFP on condition of anonymity that Liberia was at considerable risk from the disease.
"We have a 90 percent chance of having cases in Monrovia because about 80 percent of goods on the Liberian market come from Guinea," he said.