Drains and washing places of the Indus cities

The Indus civilization flourished in the third millennium BCE in what is now Pakistan and northwest India, with a sphere of influence of more than 1,000,000 square kilometers. Its best-preserved city, Mohenjo-daro in Sindh, was discovered in 1922. The lower town was laid out along streets that crossed at right angles, a plan that included systems of sanitation and drainage.

Excavators at Mohenjo-daro describe substantial houses of baked brick with paved washing or toilet areas and the elaborate drainage facilities typical of the civilization. UNESCO's description of the site lists public baths, wells, soak pits for disposing of sewage and an elaborate drainage system. At Harappa, another of the great cities, a sewage drain was built under the southeastern gateway.

The late mature phase, from about 2200 to 1900 BCE, combined planned cities, sanitation facilities and careful water management with long-distance trade and standard weights and measures. After 1900 BCE, in the Late Harappan phase, Harappa's population density fell, settlement pulled back to the core of the city, the plan grew disorganized, and sanitation declined.

Skeletons from Harappa record what followed. In a 2013 study, Gwen Robbins Schug and colleagues found lesions consistent with leprosy in 3.0 percent of the 66 people in the cemetery known as R-37, in 7.7 percent of the 26 in the later Cemetery H, and in 21.7 percent of the 23 in Area G, an ossuary outside the southeastern wall just beyond the sewage drain. Two of the 26 in Cemetery H had lesions consistent with tuberculosis. Infection and infectious disease became more common over time, and the communities that were socially and economically marginal were the most affected.