During World War I, soldiers in the trenches faced harsh conditions that fostered the spread of disease and infection. Overcrowding, poor sanitation, and waterlogged ground created an ideal environment for illnesses like trench fever, which was caused by bacteria transmitted through lice bites. The cramped, muddy conditions left soldiers with few opportunities to wash or change clothes, making it nearly impossible to eliminate lice. Dysentery, caused by consuming contaminated food and water, spread rapidly, leading to severe dehydration and weakness.