Diseases endemic in the trenches during World War I included trench foot, trench fever (similar to epidemic typhus), and trench mouth (acute necrotizing ulcerative gingivitis.

The disease during World war 1 was smallpox and typhoid. However, louse-borne typhus killed 2–3 million soldiers and civilians on the Eastern Front, and the war's end in November 1918 was hastened by an influenza pandemic that had begun in January 1918 and eventually claimed the lives of an estimated 50 million.