You are more likely to be killed by an infection than any other disease—and of all the people in the history of the world who have died of anything, half were killed by infections carried by mosquitoes. Yet nobody seems to have made the connection between insects and disease until a little over a century ago.

Infection has been with us since the first human being caught a cold. At times the very survival of humanity has been threatened: the Black Death killed a third of the population of Europe, while in modern times Spanish Flu killed tens of millions in just a few weeks. The Hong Kong chicken virus outbreak in 1997 had the potential to spark an even more devastating pandemic. Meanwhile new and terrible diseases such as Ebola and AIDS are appearing all the time.

This episode of Kill or Cure examines the long and bitter struggle for understanding that ultimately led to modern antibiotics, and then drug-resistant bugs. It’s a journey that takes us from the mountains of Peru to the world’s largest mass grave in London, England, and into the Centres for Disease Control, where the most dangerous bugs on the planet are caged.