The United Nations public health arm, the World Health Organization (WHO) said that the number of deaths in Guinea, the hardest-hit country, has reached 264, while 49 had died in Sierra Leone and 24 in Liberia since February.

The WHO, which monitors disease outbreaks, reported the figures on Wednesday. It said 47 new cases, and a further 14 deaths were reported across the region over the last week. The outbreak has put local systems under strain, despite the presence of international experts.

The Ebola virus is one of the world's most virulent diseases with a case fatality rate of up to 90 percent. Those at higher risk of infection are health care workers, family members and other who come into close contact with sick and deceased patients, according to the WHO.

Researchers have developed a vaccine which protects chimpanzees from the disease, but a vaccine for humans has not yet been trialed.

The outbreak is believed to have started in Guinea before touching Sierra Leone and Liberia, where cases were reported again recently after two months with no new cases being cited.

Ebola outbreaks are unusual in West Africa. Fear of the disease, which has no known cure, has hampered efforts to isolate victims.

jm/kms (AFP, AP, Reuters)