In the 14th century, a devastating plague known as the Black Death claimed an estimated 75 million lives.

Dr. Maurice Hilleman was already an expert in viruses and vaccines when a strange flu broke out in Hong Kong in 1957. But only he saw the threat it could pose around the world.

Could a microbe really cause the extinction of the human race? This video clip explores the possibility that SARs or a superflu could wreak havoc on human life on Earth in a fashion similar to the Black Plague.

Get the full story behind the aches, pains and dangerous history of the flu.