Why did the Ebola outbreak occur in west Africa?

news24

The Ebola outbreak in west Africa took many an expert by surprise by erupting thousands of kilometers from its origins in central Africa.

The Ebola virus species that has killed more than 4,000 people in west Africa caught everyone by surprise when it erupted thousands of kilometres from its historical hotbed.

The outbreak, experts say, revealed just how little we know about the deadly agent.

What is the virus' natural range? Are there limits? Can they shift?

"Previously we were under the impression that this problem would be predominantly restricted to central Africa. Clearly, that is not the case," University of Warwick virology professor Andrew Easton told AFP.

"This outbreak emphasises that viruses do not respect borders."


Different species of Ebola virus

Prior to the west African outbreak, the Zaire species of Ebolavirus had killed just under 1,100 people, all of them in the Democratic Republic of Congo (DRC), Congo and Gabon, since the disease was first recorded in 1976.

Zaire is the deadliest of the four African species of Ebolavirus, part of a family of viruses that causehaemorrhagic fever. A fifth, the Reston Ebolavirus, has been recorded in Asia.

How the virus found its way into the human population of west Africa remains, for now, a mystery.

Fruit bats are believed to be the virus' natural reservoir in the wild -- they do not fall ill from it, but can infect apes and monkeys and small antelopes, even humans directly.

Humans become exposed to the virus if they kill and butcher infected animals for food, or bushmeat, a practice that is common in parts of west Africa's tropical forests.

What seems likely is that last December, a single human caught the virus this way, and then kicked off a transmission chain in Guinea, Liberia and Sierra Leone.