3/3. Killer microbes are the tiny bugs that kill in minutes and can wipe out entire cities. Al Kresta tells how he fell victim to a flesh-eating type that devoured most of his leg. Plus a visit to the village destroyed by the nightmare virus Ebola, and the fate of New Yorker John Tull who was diagnosed as having bubonic plague. Narrator Ross Kemp. Director Jeremy Turner ; Series producer Anne Laking (S)