John Snow raced to discover the causes of the cholera epidemic that swept Broad Street. He went door-to-door talking to the locals, then surveyed government records for extra clues. He began to craft a map of deaths, and drew the first Voronoi Diagram to assess the victims' proximity to the pump. All but 8 of the 84 victims were closer to the Broad Street Pump (and hence more likely to use it) than any other pump, and most of the remainder had daily commutes that took them past the pump. He also noticed that a local workhouse and a tavern were conspicuously cholera-free despite their proximity to the pump, and found that they had access to their own drinking supplies which unbeknownst to them had kept them safe. With his evidence in hand, he met with the local health commission and convinced them to deactivate the Broad Street Pump. But his theory was still not widely accepted, and after the epidemic passed everything returned to normal. At last, a local pastor named Henry Whitehead set out to debunk the wild theories about what had caused the epidemic in his parish. He doubted Snow's results, but as he investigated, he found more evidence that backed them up. His relationship with the neighborhood also meant he could get information Snow couldn't, and it was thus that he found Patient Zero: a baby who died two days before the epidemic, and whose mother had been throwing her dirty diapers in a cesspit under the house. The government investigated and found that the poorly-built cesspit had begun leaking into the Broad Street Pump's water supply, infecting all who drank from it with cholera passed along in the baby's diapers. It would take many years before John Snow's theory became accepted fact, but his research paved the way for the modern medical field of epidemiology.
