Dysentery

Dysentery is an infection of the intestine, mainly the colon, that causes frequent diarrhoea containing blood and mucus, cramping pain and often fever. Most cases are bacillary, caused by Shigella bacteria, or amoebic, caused by the parasite Entamoeba histolytica. Both spread by the faecal-oral route: through contaminated water, food, hands and flies.

The older English name was the bloody flux. Wherever large numbers of people lived close together without clean water or proper latrines, it followed them: into sieges, camps, troopships, prisons and refugee columns.

Kiyoshi Shiga identified the bacillus that now carries his name in Japan in 1897. Before that, armies knew dysentery only by its symptoms. Where commanders understood the link with filth, they fought it by siting latrines away from water and moving camps. Sanitation, more than medicine, decided how badly it struck.

1. Contamination. Faeces from an infected person reached water, food or hands. Flies carried it from open latrines to food.
2. Infection. A very small dose of Shigella is enough to cause illness, so it spread fast in crowded camps.
3. Illness. Repeated bloody diarrhoea, pain and fever drained the body of water and salts. Dehydration and exhaustion killed many.
4. Prevention. Latrines dug away from water and food, boiled or treated water, fly control and handwashing. Effective treatment came only in the twentieth century, with antibiotics and oral rehydration.

• The American Civil War, 1861–1865. Diarrhoea and dysentery were the leading causes of death from disease in the Union army, according to its own medical history.
• Gallipoli, 1915. In the summer heat, flies from open latrines and unburied bodies spread dysentery through the Allied trenches on the peninsula. Large numbers of men were evacuated sick.