![A bat is trapped in a net to be examined for possible viruses – including Ebola – at a secure laboratory in Franceville, Gabon. Photograph: Steeve Jordan/AFP](/sites/default/files/bats_pandemics_sm.jpg)
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How do you predict where a deadly tropical disease such as Ebola, possibly the most virulent in the world, will appear next? Since it first emerged in a small town on the edge of a Congolese forest, it has broken out in seven other African countries, often thousands of miles apart. Sometimes it has spilled out of remote rainforest and then disappeared for years.