The Epstein-Barr virus (EBV) was discovered in 1964. At the time, the very idea of a virus underlying a cancer was revolutionary. Cancer is, after all, not catching. Even now, the idea of a virus causing cancer surprises many people. But Epstein-Barr, named after its discoverers, Sir Anthony Epstein and Dr Yvonne Barr, is fascinating for other reasons too. Almost everyone carries it, yet it is only under certain circumstances that it produces disease. It has been associated with different, apparently unrelated, diseases in different populations: Burkitt's Lymphoma, producing tumours in the jaw, in African children; a nasal tumour in China; glandular fever in Europe and the USA; and the majority of cases of Hodgkin's Disease everywhere. This book tells the story of the discovery of the virus, and the recognition of its connection with these various diseases - an account that spans the world and involves some remarkable characters and individual stories.Readership: Popular science readers interested in the biological sciences and the history of medicine.