Scientists at the United States Centers for Disease Control (CDC) in Atlanta, Georgia, identified the virus in tissue samples sent earlier this week from Kikwit, the Zairean city where the outbreak is focused.
Bob Howard, a spokesman for the CDC, said: "Of the 22 samples we received from 16 people who either became ill or died, samples from 14 people tested positive for the presence of Ebola."
This is the first confirmed outbreak among the general public since 1979, when the virus killed about 200 people in Sudan. The only other known outbreaks occurred in 1976, when nearly 300 Zaireans died, and last year when a Swiss scientist working in Ivory Coast became infected after dissecting a monkey.
A team of scientists from the World Health Organisation arrived in Kikwit, in south-western Zaire, earlier this week to investigate the outbreak, which has killed 59 to 180 people and affected many others.
The WHO said: ''The experts found the 350-bed city hospital abandoned but for about 20 ill patients. In view of the dispersal of patients and staff from the hospital, the WHO believes that more cases of Ebola disease will occur in the vicinity.''
Already, the WHO team has received reports of about 20 further cases of suspected Ebola in a second hospital some 60 miles south of Kikwit which received one of the Kikwit patients.
Ralph Henderson, an assistant director-general at the WHO, said: "Given that many patients have left the Kikwit hospital, we must expect some additional transmission of the disease. However, we believe this will be limited to people who are in prolonged contact with sufferers of the disease. It is unlikely this outbreak will have implications for Zaire as a whole or for international travel.''
Dr Stephen Ostroff of CDC said the first questions the team will try to answer in Kikwit are where the disease is focused and how it is being transmitted. "Once they determine where the disease is occurring and how it's being transmitted, then they'll be able to much better answer what the risk is to other people in the area."
The Foreign Office yesterday repeated its advice for Britons to avoid travelling to Zaire, which had been in force already because of the unstable political climate and general breakdown in law and order. According to reports on Zairean state television, the army appears to have sealed off Kikwit and its half a million residents.
The Zairean authorities are concerned about the Ebola virus spreading to the capital, Kinshasa. According to local people, soldiers manning the cordon around Kikwit have taken bribes to allow people through.
The Ebola virus causes fever and massive internal haemorrhaging. People die usually within a week from extensive blood loss. Scientists have not yet identified the organism that acts as the virus's host animal, although they know that African monkeys can become infected and transmit the agent to humans.Reuse content