U.N. health officials confirmed today that a disease killing scores of people in Congo Republic was an outbreak of ebola virus and warned that the highly lethal hemorrhagic fever could still be spreading.

"We're not suggesting that this is over or even contained. We're treating it as an active outbreak," said Iain Simpson, a World Health Organization spokesman in Geneva.

So far, 73 people have been infected, of whom 59 have died, according to WHO investigators. Government health officials in the tiny West-Central African nation report 80 cases and 67 deaths.

The Cuvette West region, where the deaths have occurred, has been quarantined by the government since last week.

Blood samples drawn from patients in the region tested positive for ebola virus, said Josef Mboussa of the country's Health Ministry.

The disease, which is spread through bodily fluids, causes rapid death through massive blood loss in as many as 90 percent of those infected. Primates that are hunted by many Central Africans for food can also carry the virus.

Ebola's incubation period of two to 21 days makes it difficult to gauge how quickly the outbreak may be moving, Simpson said.

The forested Cuvette West region has 30,000 inhabitants spread among provincial towns and small villages. Efforts to investigate the outbreak have been stymied as villagers, terrified by ebola's horrific symptoms, have fled from health workers wearing head-to-toe protective suits.

Anthropologists have been sent to the region to help explain the disease.