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 VictorianLondon (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 book incorporated the idea of gemeinschaft, dealing with the effects of an epidemic in a city of common values, language, and traditions. 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. Dr. John Snow was a revered anesthetist who carried out epidemiological work in Soho, London. Around the mid-1850s Snow figured out the source of Cholera contamination to be the drinking water from the Broad Street Pump. The book was released on 19 October 2006. The Cholera outbreak from 1848-49 killed approximately 54,000-62,000 humans in London, and the outbreak from 1853-54 killed an estimated 31,000 humans in London.