By Alphonso Toweh and Saliou Samb
MONROVIA/CONAKRY, March 25 (Reuters) - West African nations scrambled on Tuesday to contain an outbreak of the deadly Ebola virus suspected to have killed at least 59 in Guinea, with people presenting symptoms of the disease reported in neighbouring Sierra Leone and Liberia.
Health authorities in Liberia said five out of six people who crossed the border from Guinea to seek treatment and showed symptoms of the fever had died.
Liberia's Chief Medical Officer Bernice Dahn said it was not confirmed if the cases were Ebola, one of the most lethal infectious diseases known to humans, and tests were being carried out.
The World Health Organisation (WHO) said a total of 86 suspected cases, including 59 deaths, had been reported in southeastern Guinea near the border with Sierra Leone and Liberia. Laboratory tests have confirmed 13 cases of Ebola in Guinea so far, the first outbreak of the disease in West Africa.
"The patients we have seen thus far have similar symptoms to those of the people in Guinea," Dahn said. "Those people had the sickness and crossed over into Liberia's Lofa county for treatment. Five died."
Samples taken from those who died in Liberia had been sent to Conakry for testing, according to the Geneva-based WHO.
In Guinea, authorities have taken steps to quarantine suspected cases in the districts of Guekedou, Macenta, Nzerekore and Kissidougou.
In neighbouring Sierra Leone, authorities set up a taskforce after the death of a 14-year-old boy who had attended the funeral of a suspected Ebola victim. Authorities are yet to confirm if the boy died of the disease.
Sierra Leone was receiving help from the WHO and the U.S. firm Metabiota, which investigates infectious disease threats, said Chief Medical Officer Brima Kargbo.
Initial reports indicated a Canadian who showed Ebola-like symptoms after travelling to West Africa had tested negative for the virus, WHO spokesman Tarik Jasarevic told reporters.
Ebola was discovered in 1976 in then-Zaire, now Democratic Republic of Congo. Scientists have identified the outbreak in Guinea as the virulent Zaire strain of the virus.
Because people who fall sick with it tend to vomit, have diarrhoea and suffer both internal and external bleeding, their bodies are often "covered in virus", explained Peter Piot, one of the co-discoverers of Ebola and now director of the London School of Hygiene and Tropical Medicine.
This means anyone in close contact with them - such as nurses, doctors and carers - is at risk, he said.
Esther Sterk, a tropical diseases specialist at the international medical charity Medecins Sans Frontières, said after an incubation period of between 2 and 21 days, the virus causes a raging fever, headaches, muscle pain, conjunctivitis and weakness, before moving into more severe phases of causing vomiting, diarrhoea and hemorrhages.
"Patients may have heavy bleeding, including from the nose or via their urine," she said in a briefing note on the disease.
She added, however, that while dangerous, Ebola remains rare. Since the virus was discovered in 1976, around 2,200 cases have been recorded. Of those, 1,500 were fatal.
The last major outbreak of the Zaire strain was in 2007, when 187 people died in Congo, a fatality rate of 74 percent.
Scientists are not clear how the virus - which also infects animals including bats, believed to be a major reservoir of the disease - crossed the continent from Sudan, Congo and Uganda.
With ethnic and family ties and trade making cross-border travel common in the region, the outbreak in Guinea is causing concern in nearby West African nations.
Mali said it was working with the WHO to put in place preventive measures, including stronger border control health checks, and a mechanism for coping with potential victims.
The WHO's Jasarevic said the main areas authorities should focus on were infection control, scaling up laboratory testing facilities and ensuring the best clinical management of confirmed cases of infection.
"It's also about working with health workers so they know how to treat patients properly so they don't fall victim themselves," he said.
(Additional reporting by Umaru Fofana in Freetown, Kate Kelland in London and Stephanie Ulmer-Nebehay in Geneva; Writing by Bate Felix; Editing by Daniel Flynn and Janet Lawrence)