A special edition looking at how the world has battled deadly viruses over the past 100 years, We have eyewitness accounts of the 1918 flu, and the recent struggle against SARS, we hear how a vaccine saved millions from Polio, and the moment the world discovered the killer viruses known as Marburg Fever and Ebola in the 1960s and 70s.

(Photo: An American policeman wearing a mask to protect himself from the outbreak of Spanish flu. Credit:Topical Press Agency/Getty Images)