JOHANNESBURG - A virus new to humanity, or an old acquaintance dressed up in slightly new clothes, the disease that so far appears to have achieved a 100% kill rate in Johannesburg, is now up against the full might of humanity's scientific detectives.

So far three people have died from the mysterious disease, which has retained its anonymity through an extensive first round of laboratory testing for viral haemorrhagic fevers.

Based on the pattern of disease and a suspected tick bite on the first patient, the pathogen -- let us call it Virus X -- is suspected of being Crimean-Congo Haemorrhagic Fever (CCHF) or Lassa fever, or one of their close relatives.

Such a diagnosis would be relatively good news if Virus X has infected other people, because these pathogens are estimated to kill about 30% of their victims. The nastier haemorrhagic fevers such as Ebola and Marburg have achieved kill rates of up to 90% in some outbreaks. There is also one antiviral, ribavirin, which can be used against CCHF and Lassa.

In the words of one World Health Organisation expert, haemorrhagic viruses kill by "melting the organs". They disrupt the body's internal structure and damage the clotting mechanism. The patient effectively bleeds to death either internally, or with dramatic bleeding from all orifices detailed in several books and films. Blood pressure falls and the patient dies from multi-organ failure.

Professor Guy Richards is an intensive care specialist at Charlotte Mxenge Johannesburg Hospital and one of the doctors who treated the outbreak of Ebola in Johannesburg in the late 1990s. In that case the original patient, a man flown in from Congo, survived. Sadly the nurse treating him died.

He says the haemorrhagic fevers typically attack the endothelial cells lining the blood vessels. The blood vessel system, with its myriad branching arteries, veins and capillaries, is the largest organ inside the body. The membranes of these cells are damaged and fluids leak in and out of the holed cells which are no longer able to maintain their cohesion with their neighbours. Blood vessels collapse, blood pressure falls and the patient dies.

Usually the best medical workers can do is try to keep the patient alive by giving fluids and keeping them cool, and hope that the individual's immune system will be able to fight off the pathogen. Another infectious disease doctor says that the problem is that measures to help the patient, such as inserting drips or tubes to help them breathe, can then trigger further bleeding.

Samples of Virus X are undergoing further tests at the National Institute of Communicable Diseases in Johannesburg, which is one of the few laboratories in any developing country with the infrastructure and skills to test for such dangerous and rare pathogens. The institute's Lucille Blumberg, who leads the laboratory investigations, says that it will probably take several days for Virus X to be identified -- and there is a chance it could be a new virus making its way on to the world stage.