病毒为何致命

Just months ago, the world stood in fear of an emerging new disease that threatened to kill millions. A new flu variant H1N1 had arrived. In the UK alone, 65,000 deaths were predicted. Yet to date, these dire warnings have not materialised.
　　If this latest pandemic has taught anything, it is just how little is understood about the invisible world of viruses. But that has not sto...