Killers on the loose: the deadly viruses that threaten human survival

The journey in 2008, booked through an adventure-travel outfitter, took them to the Bwindi Impenetrable Forest , home to mountain gorillas. While there, the operators offered an optional trip, to a place called the Maramagambo Forest, where the chief attraction was a peculiar site known as Python Cave. African rock pythons lived there, languid and content, grown large and fat on a diet of bats, the Guardian reports.

Most of the other travellers didn't fancy this trip, Taal told me. "But Astrid and I always said, maybe you come here only once in your life, and you have to do everything you can."

Inside the cave, the footing was bad: rocky, uneven, slick with guano. The ceiling was thick with bats, big ones, many thousands of them, agitated at the presence of human intruders. Astrid and Jaap kept their heads low and watched their step, trying not to slip, ready to put a hand down if needed. "I think that's how Astrid got infected," he told me. "I think she put her hand on a piece of rock [covered with bat droppings]. And so she had it on her hand."

No one had warned Joosten and Taal about the potential hazards of an African bat cave. They knew nothing of a virus called Marburg , first identified in 1967 and thought to be carried by bats (though they had heard of Ebola , another filovirus). They stayed in the cave for only about 10 minutes. Then they left, visited the mountain gorillas, did a boat trip, and flew back to Amsterdam. Thirteen days after the cave visit, at home in Noord-Brabant, Astrid fell ill.

At first it seemed no worse than flu. Then her temperature went higher and higher. After a few days she began suffering organ failure. Her doctors suspected Lassa fever and moved her to a hospital in Leiden, where she developed a rash and conjunctivitis; she haemorrhaged. She was put into an induced coma, a move dictated by the need to dose her more aggressively with antiviral medicine. Before she lost consciousness, Taal went back into the isolation room, kissed his wife and said to her, "Well, we'll see you in a few days." Blood samples, sent to a lab in Hamburg, confirmed the diagnosis: Marburg. Astrid worsened. As her organs shut down, she lacked oxygen to the brain, suffered cerebral oedema, and before long she was declared brain-dead. "They kept her alive for a few more hours, until the family arrived," Taal told me. "Then they pulled out the plug and she died within a few minutes." The doctors, appalled by his recklessness in kissing her goodbye, had prepared an isolation room for Taal himself, but that was never needed.

The news of Astrid Joosten's death carried far. She was the first person known to have left Africa with an active filovirus infection and died. Back in 1994, a Swiss graduate student from Ivory Coast had recovered. Did any other person, apart from those two, ever pass through an international airport and depart the continent with Ebola or Marburg virus incubating in his or her body? No one of whom the experts were aware. Astrid Joosten's case proved that Marburg could travel in a human, though it didn't travel as well as Sars or influenza or HIV-1 . Five thousand miles away, in Colorado, another woman heard the news with a shudder of recognition. She had visited Python Cave, too.

For full version go to