Horizon: Why Do Viruses Kill?

Just a matter of months ago, a new disease threatened to kill millions. In the UK alone, 65,000 deaths were predicted. Yet dire warnings about new flu variant H1N1 have not materialised. If this latest pandemic has taught anything, it is just how little is understood about the invisible world of viruses. Horizon follows the leading researchers who are attempting to unravel the many secrets of viruses to understand when and why they kill