In the wake of the swine flu outbreak, virologist Dr Mike Leahy uses over 50 years of BBC archive to explore the history of pandemics - infectious diseases caused by bacteria, viruses and parasites.
Inspired by the Horizon back catalogue, he tells the extraordinary story of smallpox, one of the most violent killers in history, as well as the success of mass vaccination and the global politics of malaria.
Through the lens of television the programme charts our scientific progress from the early steps in understanding AIDS to the code-cracking of SARS and deadly predictions of bird flu.
Each pandemic episode tells us something about the world and our place within it. In his journey through the ages Dr Leahy charts science's ongoing battle with nature and questions which one is winning.