Since the isolation of the first virus in 1892 scientists have made tremendous advances by asking one question at a time and building on the answers. Dr. Levine celebrates the successes that have come from viral studies - the development of a wide range of vaccines, the eradication of smallpox, and the insights into the origins of cancer. He also examines the challenges we still face, with a series of interconnected chapters on the specific viruses behind some of our most urgent public health problems, including the viruses that cause AIDS, influenza, herpes and hepatitis. A concluding chapter on the origin and evolution of viruses touches on some of the most provocative issues in molecular biology today. Viral infections continue to be an immediate health concern of imposing proportions. Viruses is written for the general reader eager to know how we study and confront these diseases and where today's research may lead.