The deaths in recent days of physicians highlighted the serious risks facing health workers trying to help counter the latest Ebola outbreak in West Africa.

A Liberian government official said on Sunday that high-profile Doctor Samuel Brisbane had died from the virus. A Ugandan doctor working in Liberia had died earlier this month.

It was also announced that two US health workers had been infected in the same Liberian compound. Dr Ken Brantly, a medical center director in the outskirts of the capital, Monrovia, and hygienist Nancy Writebol were both reported to be in a stable but serious condition, receiving intensive treatment in isolation.

"It's a shock to everyone on our team to have two of our players get pounded with the disease," said Ken Isaacs, vice-president of Christian charity Samaritan's Purse.

The first death from Ebola in Sierra Leone's capital Freetown has also been recorded. Hairdresser Saudata Koroma was forcibly removed from hospital by her family, sparking a frantic search that ended on Friday. However she later died while being transported to a treatment center in Sierra Leone's east.

The World Health Organization says at least 660 people have died in recent months from what has become the deadliest outbreak ever of Ebola.

Most of deaths have been in Guinea, where the outbreak is believed to have begun - followed by Sierra Leone and Liberia.

Ebola is a form of hemorrhagic fever which is deadly in up to 90 percent of cases. Symptoms include fever and sore throat, which escalates to vomiting, diarrhea, as well as internal and external bleeding.

There is no known cure for the highly-contagious disease, although early detection and treatment improves a patient's chance of survival.

jr/pfd (AP, AFP)