Since the very emergence of civilization, humanity has coexisted with invisible and deadly enemies - viruses. Smallpox claimed more lives than all man-made disasters and the bloodiest wars of the 20th century; yellow fever prevented Napoleon from creating a colonial empire and nearly prevented the construction of the Panama Canal. Virologist Professor Michael Oldstone, based on the testimony of contemporaries of terrible epidemics and scientists, "microbial hunters," shows how deep the impact of viruses on the life of mankind. You have to learn success stories - about hero doctors who created vaccines against smallpox and yellow fever, overcoming everyday and religious prejudices, and competition between polio vaccines, which saved people from fear of becoming disabled. Of course, there is a place in the book for the stories of the ongoing struggle: due to business and government mistakes in collecting donated blood - with an outbreak of hepatitis; due to false information that the measles vaccine causes autism in children, with fear and distrust of doctors and the state. And scientists continue to fight new threats that, appearing suddenly, as if from a Pandora's box, remind us that we are taking health for granted in vain.