How did disease spread in world war 1?

During World War I, disease spread rapidly due to the close quarters of soldiers in trenches, unsanitary conditions, and the movement of troops across different regions. Outbreaks of illnesses such as influenza, dysentery, and typhus were exacerbated by malnutrition and the lack of medical care. The return of soldiers to their home countries further facilitated the spread of diseases, impacting civilian populations as well. Additionally, the mass mobilization of troops created ideal conditions for the transmission of contagious diseases.