In October 1918, an Allied army (Egyptian Expeditionary Force) in Palestine experienced simultaneous epidemics of falciparum malaria and influenza during the cavalry campaign that defeated the Turkish Army.

Malaria infection occurred 2 weeks after the advance of cavalry units into areas without environmental mosquito control. Pandemic influenza, now thought to be an A/H1N1 strain, struck at the same time.

In the Egyptian Expeditionary Force of 315 000 soldiers, 773 died from malaria and 934 from influenza–pneumonia. Disease casualties outnumbered those due to combat by more than 37 to 1.

Simultaneous infectious disease epidemics can cause mass casualties, capable of overwhelming any health service.