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When a cholera outbreak gripped a London neighbourhood in 1854, physician John Snow carefully mapped its deaths. The thin bars he traced under each address clustered around a water pump on Broad Street, which turned out to be the source of the bacteria. Snow’s studies of disease patterns won him recognition as the father of modern epidemiology—and crushed the prevailing theory that cholera was spread by bad air.

Faced with the same challenge today, Snow might use a tablet computer. In mid-January, as the Indian city of Allahabad began ushering in millions of Hindu pilgrims for the religious festival Kumbh Mela, emergency physician and epidemiologist Gregg Greenough settled into a temporary field hospital with his tablet computer. He and his team from the Harvard School of Public Health were on the lookout for signs of influenza, tuberculosis, cholera and other diarrheal diseases. The plan is to record the temporary residence of each pilgrim admitted to hospital and plot it on a digital map that geolocates the festival’s toilets and drinking water. “We’re helping them digitize the data and analyze it in real time,” says Greenough. “It should help keep the pulse of the community and see if anything is emerging so they can act on it quickly.” Continue…