This well researched films describes the power of viruses, which have caused unimaginable suffering and death throughout history. But for of all their destructive power, many scientists believe they are the earliest form of life on Earth and responsible for our very existence.

It is the virus hunters who are leading the life and death battles against viruses. Ken Stedman hunts extreme viruses that live in the boiling acid pools of Lassen Volcanic National Park in California. Donald Henderson is responsible for wiping out smallpox —it is the only virus that mankind has conquered. Within a year of its eradication, AIDS emerged to become a worldwide pandemic. Ebola, Marburg, SARS, West Nile Virus and a host of new infectious diseases soon followed. The film follows Steven Jones, a scientist with WHO, who has been sent to Angola to contain a deadly outbreak of Marburg virus. Kristine Smith is a veterinarian—a profession that has become the new first line of defense against infectious outbreaks. Close to 75 percent of new human diseases are transmitted by animals. Smith and her team show that man is bringing these diseases onto himself through illegal and legal wildlife trade, travel, population growth, and environmental destruction.

The documentary also explores such chronic diseases as cancer, heart disease, autism, multiple sclerosis and mental illness, which are now suspected of being caused by viruses.