CONAKRY, Guinea (AP) — Health workers in protective hazmat suits treated patients in quarantine centers on Tuesday in a remote corner of Guinea where Ebola has killed at least 60 people in West Africa's first outbreak of the deadly virus in two decades.

Seven patients are being hospitalized at one isolation ward in Gueckedou in southern Guinea, while two others are being treated elsewhere, said Doctors Without Borders. The aid group said it is sending mobile teams into the surrounding countryside in search of people who may have been exposed since the first cases emerged last week.

"To confine the epidemic, it is critical to trace the entire transmission chain," said Dr. Esther Sterk, a tropical medicine adviser for the medical group. "All individuals who have had contact with patients who may be contaminated are monitored and isolated at the first sign of infection."

Six of the seven blood samples sent to France from Guinea had tested positive for Ebola, specifically the Zaire strain of the disease originating from Congo which has up to a 90 percent fatality rate, the World Health Organization said Tuesday.

Ebola has no vaccine or specific treatment. Its initial symptoms — high fever, weakness and headache — can mimic malaria, a much more common disease in West Africa. Once the virus has caused hemorrhaging, though, victims can start vomiting blood or bleeding from their nose and gums.

Some 1,500 of the 2,220 cases recorded since the virus was first discovered in 1976 have been fatal, experts say. So far the fatality rate in Guinea has been 70 percent, according to Dr. Sakoba Keita, a spokesman with the health ministry.

Those grim statistics are fueling fear amid the first outbreak in this part of West Africa in 20 years. So far at least 60 people have died in Guinea, a desperately poor country with limited health facilities, Keita said.

The outbreak has raised alarm in neighboring countries. Across the border in Liberia, officials are already investigating eight cases — including five deaths — suspected of having links to the Guinea cases. Those patients traveled across the border into Liberia in search of medical treatment, health officials said there.

Authorities in Sierra Leone and Ivory Coast say they are closely monitoring along their borders for possible cases.

The last case reported in West Africa was in Ivory Coast back in 1994. More recent outbreaks have emerged in Congo and Uganda.

It is unclear why the virus has now emerged in Guinea though Dr. Armand Sprecher, a public health specialist with Doctors Without Borders, said the virus is carried by bats in the region.

"It comes out of its reservoir when people eat bats or when bats share a tree with chimps or gorillas who are eating fruit," he explained. "The chimps and gorillas become sick and become easy targets for bush meat hunters."

Grieving relatives also can contract the virus when they come into contact with the bodies of victims during communal funerals, health officials say. Other victims have included health workers who treated the patients before the Ebola outbreak was identified.

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Larson reported from Dakar, Senegal. Associated Press writer Jonathan Paye-Layleh in Monrovia, Liberia also contributed to this report.