Answer:
due to creation of concentration camps.
Step-by-step explanation:
Influenza epidemic starts in the military and concentration camps which affected the soldiers and spreads to the local people when the soldiers return to their homes. This disease cause by the virus named H1N1 virus. The World War I can be called a true "world war'' because major countries of the world participated in this war. In this war, some countries are present in one group while on the other hand, other countries join the other group for mutual benefits and purpose.