Within hours he was diagnosed with Crimean-Congo Haemorrhagic Fever, a virus nasty enough for him to be put onto a military transport aircraft for transfer to an isolation hospital in London.

ECONOMIST: Where and when will the next pandemic emerge?

Angola sealed its border with Congo to contain an outbreak of Marburg virus , an incurable Ebola-like haemorrhagic disease that has killed at least 146 people.

ECONOMIST: After Pope John Paul II

It took several years for the virus to break out of Congo's dense and sparsely populated jungles but, once it did, it marched with rebel armies through the continent's numerous war zones, rode with truckers from one rest-stop brothel to the next, and eventually flew, perhaps with an air steward, to America, where it was discovered in the early 1980s.

ECONOMIST: A global disaster

In West Africa the Ebola virus killed 5, 000 gorillas in just one corner of the Republic of the Congo.

FORBES: Meet the Relatives

Extensive ecological studies are underway in three African countries, including DR Congo, to try to find the "reservoir" - this work essentially involves checking for signs of the virus in thousands of different species of animal, in order to identify the carrier.

BBC: Africa's emerging virus threat