The outbreak that began in July in the Democratic Republic of Congo is similar to earlier ones in that central African region, genetic testing of viruses shows. At least 69 people, including eight health workers, are believed to have been infected, and 49 have died.
The study was led by the World Health Organization and researchers from France and Canada. It was published online Wednesday by the New England Journal of Medicine.
Ebola first appeared in 1976 in Congo and has caused periodic outbreaks there and in other central African countries. It had not been detected in West Africa until the current epidemic — the worst ever of Ebola — began earlier this year.
So far, more than 8,900 people have been infected and more than 4,400 have died, mostly in Guinea, Liberia and Sierra Leone. Officials say the epidemic is not even close to being brought under control.
Health experts think the initial cases in each outbreak got it from eating or handling Ebola-infected animals, then spread it person-to-person. The exact source in nature has not been proved but the leading suspect is a certain type of fruit bat.
Other animals can be infected and may spread the disease. The WHO says chimpanzees, gorillas, monkeys, forest antelope and porcupines might play a role. Even pig farms may amplify infection because of fruit bats on farms.
For the new study, researchers analyzed viruses from the current Congo outbreak and found them extremely similar to a Zaire Ebola strain that caused previous outbreaks in the Congo region. The virus is different from the Zaire strain causing the larger epidemic in West Africa, suggesting that a separate source in nature seeded each outbreak.
Still, officials say that getting Ebola from an animal is a much smaller risk than catching it from an infected person once an outbreak is ongoing. The research on the viruses may help pinpoint the animal sources and prevent future cases.
Marilynn Marchione can be followed at http://twitter.com/MMarchioneAP