What major health issue plagued soldiers in the trenches during WWI?

The major health issue that plagued soldiers in the trenches during World War I was trench foot. This condition arose due to soldiers standing for long periods in waterlogged trenches, leading to swelling and pain in the feet, as well as potentially severe tissue damage. The unsanitary conditions, along with the cold and damp environment, made soldiers vulnerable to this painful ailment, which could result in more serious complications like gangrene, sometimes necessitating amputation.

While other health issues, such as flu outbreaks, did occur during WWI, trench foot was particularly associated with the unique living conditions in the trenches. Severe frostbite, although it did affect soldiers due to the harsh winter conditions, was not as widespread as trench foot. Malaria was mainly associated with different theatres of war, particularly in tropical regions, and was not a significant concern in the European trench warfare context. Therefore, trench foot stands out as the defining health issue that compromised the wellbeing of soldiers in those specific conditions.