Emergency Spanish influenza (flu) hospital in in Brookline, Massachusetts, USA. The beds were arranged head to toe to prevent neighbouring patients from breathing on each other. The 1918 Spanish flu pandemic, which occurred in several waves between 1918 and 1920, infected one fifth of the world population and killed between 20 and 50 million, more than had been killed in the First World War. The second wave of the pandemic, from August 1918, was much deadlier than the first, with high mortality rates among young healthy adults. Photographed in October 1918.