【素材】Unit 1 文档1854 Broad Street cholera outbreak（人教）.doc

1854 Broad Street cholera outbreakBroadwick Street showing the John Snow memorial and pubThe 1854 Broad Street cholera outbreak was a severe outbreak of cholera that occurred near Broad Street (now renamed Broadwick Street) in Soho district of London, England in 1854. This outbreak is best known for John Snows discovery that cholera is spread by contaminated water.BackgroundIn the mid-19th century, the Soho district of London had a serious problem with filth due to the large influx of people and a lack of proper sanitary services. Many cellars (basements) had cesspools of nightsoil underneath their floorboards. Since the cesspools were overrunning, the London government decided to dump the waste into the River Thames. This caused massive water contamination and led to the cholera outbreak.OutbreakOn 31 August 1854, after several other outbreaks had already occurred elsewhere in the city, a major outbreak of cholera struck Soho. Dr Snow later called it the most terrible outbreak of cholera which ever occurred in the kingdom.Over the next three days 127 people on or near Broad Street died. In the next week, three quarters of the residents had fled the area. By 10 September, 500 people had died and the mortality rate was 12.8 percent in some parts of the city. By the end of the outbreak 616 people died.John Snow InvestigationOriginal map by Dr. John Snow showing the clusters of cholera cases in the London epidemic of 1854Snow was a skeptic of the then-dominant miasma theory that stated that diseases such as cholera or the Black Death were caused by pollution or a noxious form of bad air. The germ theory was not widely accepted by this time, so Snow was unaware of the mechanism by which the disease was transmitted, but evidence led him to believe that it was not due to breathing foul air. He first publicized his theory in an essay On the Mode of Communication of Cholera in 1849. In 1855 a second edition was published, with a much more elaborate investigation of the effect of the water-supply in the Soho, London epidemic of 1854.By talking to local residents (with the help of Reverend Henry Whitehead), he identified the source of the outbreak as the public water pump on Broad Street (now Broadwick Street).1 Although Snows chemical and microscope examination of a sample of the Broad Street pump water was not able to conclusively prove its danger, his studies of the pattern of the disease were convincing enough to persuade the local council to disable the well pump by removing its handle. Although this action has been popularly reported as ending the outbreak, the epidemic may have already been in rapid decline, as explained by Snow himself:There is no doubt that the mortality was much diminished, as I said before, by the flight of the population, which commenced soon after the outbreak; but the attacks had so far diminished before the use of the water was stopped, that it is impossible to decide whether the well still contained the cholera poison in an active state, or whether, from some cause, the water had become free from it.Snow later used a spot map to illustrate how cases of cholera were centred around the pump. He also made a solid use of statistics to illustrate the connection between the quality of the source of water and cholera cases. He showed that companies taking water from sewage-polluted sections of the Thames delivered water to homes with an increased incidence of cholera. Snows study was a major event in the history of public health, and can be regarded as the founding event of the science of epidemiology.In Snows own words:On proceeding to the spot, I found that nearly all the deaths had taken place within a short distance of the Broad Street pump. There were only ten deaths in houses situated decidedly nearer to another street-pump. In five of these cases the families of the deceased persons informed me that they always sent to the pump in Broad Street, as they preferred the water to that of the pumps which were nearer. In three other cases, the deceased were children who went to school near the pump in Broad Street.With regard to the deaths occurring in the locality belonging to the pump, there were 61 instances in which I was informed that the deceased persons used to drink the pump water from Broad Street, either constantly or occasionally.The result of the inquiry, then, is, that there has been no particular outbreak or prevalence of cholera in this part of London except among the persons who were in the habit of drinking the water of the above-mentioned pump well.I had an interview with the Board of Guardians of St Jamess parish, on the evening of the 7th inst Sept 7, and represented the above circumstances to them. In consequence of what I said, the handle of the pump was removed on the following day.John Snow,letter to the editor of the Medical Times and GazetteIt was discovered later that this public well had been dug only three feet from an old cesspit that had begun to leak fecal bacteria. A baby who had contracted cholera from another source had its diapers washed into this cesspit, the opening of which was under a nearby house that had been rebuilt farther away after a fire had destroyed the previous structure, and the street was widened by the city. It was common at the time to have a cesspit under most homes. Most families tried to have their raw sewage collected and dumped in the Thames to prevent their cesspit from filling faster than the sewage could decompose into the soil.Henry Whitehead InvolvementRev. Henry WhiteheadThe Reverend Henry Whitehead was an assistant curate at St. Lukes church in Soho, London, during the 1854 cholera outbrea