What is Ebola and how worried should we be about it?

Ebola, formerly known as Ebola haemorrhagic fever, is described by the World Health Organisation as "a severe, often fatal illness in humans".

It first appeared in 1976 in two simultaneous outbreaks, in Nzara, Sudan and in Yambuku, a village near the Ebola River, in the Democratic Republic of Congo.

The virus is found mainly in central and west Africa and people living in or near tropical rainforests are at particular risk.

It is introduced into the human population through close contact with the sweat, blood, secretions, organs or other body fluids of infected animals such as chimps, gorillas, fruit bats, monkeys, forest antelopes and porcupines.

In humans, the virus is spread through direct contact (through broken skin or mucous membrane) and by indirect contact with environments contaminated with such fluids.

The WHO said the disease is not contagious until symptoms develop.

Men who have recovered from the disease can transmit the virus through semen for up to seven weeks .

Early treatment improves the chances of survival.

There is no vaccine or cure. Treatment is symptomatic. Testing for the virus must be done with the highest level of biohazard protection.