The Ghost Map: The Story of London's Most Terrifying Epidemic--and How It Changed Science, Cities, and the Modern World

by Steven Johnson

A survey in 1849 examined 15,000 homes, and found that almost 3,000 had offensive smells from bad drainage, while a thousand had “privities [sic] and water-closets in a very offensive state.” One in twenty had human waste piling up in the cellar.