Thursday, May 6, 1999 Published at 22:34 GMT 23:34 UK
Mystery fever is diagnosed
The Marburg virus was isolated by microbiologists in Johannesburg
The World Health Organisation says the mysterious haemorrhagic fever that has broken out in a remote area of Eastern Congo is caused by the little-understood Marburg Virus.
The diagnosis was made from blood samples taken from the victims - mostly gold miners - and tested by the National Institute of Virology in South Africa.
However the WHO says the "latest figures are an estimated 76 cases with 52 deaths".
WHO spokesman Gregory Hartl said some of the gold miners had died of other causes. "Some deaths have now been excluded as having been caused by Marburg. They may have been malaria or something else," he said.
Victims bleed to death
Marburg victims have a high fever and bleed to death from body orifices. The symptoms led to speculation that this was an outbreak of the much-feared Ebola virus, but the WHO ruled that out earlier in the week.
As with Ebola, there is no specific treatment or vaccine for the Marburg virus.
Most of the victims were gold miners, leading to speculation that the men may have come in contact with the Marburg virus in the course of their work.
The WHO says it will be trying to find the exact source of the outbreak, but BBC East Africa correspondent Martin Dawes says access will be difficult as the area is remote and at war.
History of the virus
The virus was first identified in 1967, in the North German town of Marburg, after a laboratory worker who was taking blood from African monkeys became ill and died.
Even in the best hospitals, with the most modern facilities, the virus can be expected to kill a quarter of those who go down with it.
It is extremely rare and, for that reason alone, researchers will want to find out as much as possible about this latest outbreak.