Ebola and Marburg fevers -- which have a mortality rate of up to 80 per cent -- kill hundreds of people in the tropical forests of Central Africa each year, mainly in the Democratic Republic of Congo. The diseases work by shutting down the patient's immune system.

Using a viral database, the research team looked for parts of the Ebola and Marburg virus genes that resemble other viruses known to suppress the immune system.

They then synthesised the series of amino acids -- or proteins -- that the region of the genes produce, and tested their effects on human and monkey immune cells.

The team tested 17 such proteins, and found that 16 of them rapidly depressed the human cells' immune response and killed the cells. The other protein killed the monkey cells but not the human cells.

By targeting the newly identified series of amino acids, the researchers hope to be able to develop new drugs against these viruses, which are associated with fever, shock and bleeding. No cures or approved vaccines currently exist for either virus.

Lead researcher Ian Lipkin of Colombia University, United States says the diseases are becoming more of a global concern with increased travel, wildlife trafficking, political instability and terrorism.

The study, which went online on October 5, will be published in the December 2006 issue of the Federation of American Societies for Experimental Biology (FASEB) Journal.