Kitum Cave

Kitum Cave is a non-solutional cave developed in pyroclastic (volcanic) rocks (not, as some have presumed, a lava tube) in Mount Elgon National Park, Kenya. The cave extends about 200 metres (700 ft) into the side of the mountain. The walls are rich in salt, and animals such as elephants have gone deep into the cave for centuries in search of salt. The elephants use their tusks to break off pieces of the cave wall that they then chew and swallow, leaving the walls scratched and furrowed; their actions have likely enlarged the cave over time. Other animals including bushbuck, buffalo and hyenas come to Kitum Cave to consume salt left by the elephants. There is a lot of bat mucus deeper in the cave from fruit-eating and carnivorous bats. There is also a deep crevasse into which young elephants have fallen and died.

In the 1980s two visitors to the cave contracted Marburg virus. In 1980, a French man died from the virus, and in 1987 a Danish 15-year-old boy got sick and died after visiting the cave. Based on these cases, an expedition was staged by the United States Army Medical Research Institute of Infectious Disease (USAMRIID) in an attempt to identify the vector species presumably residing in the cave. Despite sampling a wide variety of species (including fruit bats), no Marburg was found and the animal vector remained a mystery. These events were dramatized by Richard Preston in the best-selling book The Hot Zone.

In September 2007, similar expeditions to active mines in Gabon and Uganda found solid evidence of reservoirs of Marburg in cave-dwelling Egyptian fruit bats. The Ugandan mines both had colonies of the same species of African fruit bats that colonize Kitum Cave, suggesting that the long-sought vector at Kitum was indeed the bats and their guano. The study was conducted after two mine workers contracted Marburg in August 2007, both without being bitten by any bats, suggesting the virus may be propagated through inhalation of powdered guano.