Viruses are big news. From HIV to swine flu and SARS, we are constantly concerned about new lethal infections that may spread rapidly worldwide. In this volume the author looks at the nature of viruses and our perpetual struggle against them. In recent years, the world has witnessed dramatic outbreaks of such dangerous viruses such as HIV, Hanta, swine flu, SARS, and Lassa fever. Here the author, a biologist and science writer offers a portrait of these infinitesimally small but often highly dangerous creatures. Outlining their discovery, their structure, and their modes of infection, she describes the challenges posed by them. She first relates how viruses were discovered and she unravels the intricate structures of tiny parasites that are by far the most abundant life forms on the planet. Analyzing the threat of viral infections, she recounts stories of renowned killer viruses such as Ebola and rabies as well as the less known bat-borne Nipah and Hendra viruses. She identifies wild animals as the source of the most recent pandemics, detailing the reasons behind the present increase in potentially fatal infections, and evaluating the evidence that suggests that long term viruses can eventually lead to cancer. Finally, she looks to the future to ask whether we can ever live in harmony with viruses, and considers ways to prevent the emergence of new and devastating viruses.