The Ghost Map: The Story of London's Most Terrifying Epidemic – and How it Changed Science, Cities and the Modern World is a book by Steven Berlin Johnson in which he describes the most intense outbreak of cholera in Victorian London (See 1854 Broad Street cholera outbreak) and what it means to us today, from the way we understand cities, science, disease, and the modern world. The two central protagonists are Dr. John Snow, who created a map of the cholera cases, and the Reverend Henry Whitehead, whose extensive knowledge of the local community helped determine the initial cause of the outbreak. The book was released on 19 October 2006.