An introduction to the mysterious world of the virus, this award-winning book explores the simple, but potentially deadly action of these pirates of the cell. The author explains the role of viruses in disease, our complex and marvellous defence systems, the working of vaccinations and drugs and finally our increasingly successful attempts to exploit viruses to serve our own ends. The book won the Choice award for outstanding academic book 1985/6, and is now published in paperback for the first time. It should be of interest to students of biological science, medical students, virologists, and general readers.