In Europe in 1918, influenza spread through Spain, France, Great Britain and Italy, causing havoc with military operations during the First World War. The influenza pandemic of 1918 killed more than 50 million people worldwide. In addition, its socioeconomic consequences were huge. It primarily affected Spain, Serbia, Mexico and Great Britain, resulting in hundreds of thousands of deaths. It was less severe than the second wave but still much more deadly than the initial first wave.