"The world situation in 1918 exacerbated the effects of the pandemic. Wartime conditions combined with the intrinsic pathogenicity of the virus to cause tremendous morbidity and death rates. Poor sanitation, overcrowding, and limited health services during World War I facilitated disease transmission. Wartime overcrowding was rampant. Camps for troops, hastily built to accommodate 36,000, were soon housing 45,000 young and immunologically naïve soldiers. Each day in the summer of 1918, an average of 10,000 US soldiers crammed onto ships bound for France. Civilians flooding to cities in support of war industries quickly exceeded available housing capacity. With 30% of US physicians engaged in military service, medical personnel were in short supply when the pandemic struck."