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Causes of Cholera. Two Camps. Miasmatists (M)Foul Air (FA). Robert Seymour, October 1, 1831 . Causes of Cholera. Chadwick: all smell is disease. Two Camps. Miasmatists (M)(Often smelly) Foul Air (FA) . Robert Seymour, March 1, 1832. Causes of Cholera. Thames. Two Camps. - PowerPoint PPT Presentation

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Causes of CholeraTwo CampsMiasmatists (M)Foul Air (FA)

Robert Seymour, October 1, 1831 Causes of CholeraTwo CampsMiasmatists (M)(Often smelly) Foul Air (FA)

Robert Seymour, March 1, 1832Chadwick: all smell is disease

George Cruickshank, 1832It makes me sickWe shall all have the CholeraGive us clean waterCauses of CholeraTwo Camps2. Contagionists (C)Contaminated Water (CW)

ThamesSource: Greenwood C and Greenwood J. Greenwood Map of London, 1830.

In 1830, the Southwark Water Company was located on the South bank of the River Thames between the Southwark and London Bridges. The water intake pipe went from the company to the middle of the river, a short distance to the West of the new London Bridge, which officially opened in 1831. Later in 1845 the Southwark Water Company merged with the Vauxhall Water Company to become the Southwark and Vauxhall Water Company. At about the same time, the new company closed the former Southwark Water Company (shown below), and moved up-river to Battersea.Data on 1848-1849 Cholera OutbreakThe Office of the Registrar-General, created in 1838, hired William Farr to compile statistics from birth and death certificates. One of his important contributions was to set up a system for recording the causes of death.Allowed him to create, Cholera Deaths per 10,000 people!

William FarrSOURCE: Bingham P, NQ Verlander, and MJ Cheal, John Snow, William Farr and the 1849 Outbreak of Cholera that Affected London, Public Health. 2004; 118(6):387-94

George Cruickshank, 1832

Hammersmith BridgeBattersea BridgeVauxhall BridgeNThe Thames runs from West to EastWaterloo BridgeKew BridgeWaterCL = 1 if the districts water company drew its water from the Thames between Battersea Bridge and Waterloo Bridge = 0 otherwiseSouthwark BridgeLondon Bridge

1845Figure 1. Cholera Deaths and the Elevation of Londons Reg. Districts, 1849Dependent Variable: Cholera Deaths per 10,000 people Explanatory Variables(1)(2)(3)Elevation above HighWater (# feet)

-1.326***-0.730**-0.647**(5.72)

(2.63)

(2.36)

Water Intake in CentralLondon (yes=1)

80.73***52.136***48.570***(6.19)

(3.21)

(3.05)

Average House Value ( per year)

-0.306*(1.72)

Constant110.101***41.52***74.128***86.660***(11.27)

(5.59)

(5.23)

(5.56)

Observations37373737R-squared0.4830.5220.6030.636Absolute value of t statistics in parentheses* significant at 10%; ** significant at 5%; *** significant at 1%Table 1. What Explains Cholera Deaths in London in 1849?

^OLS Fitted LineInterpretation of the slope: each additional foot of elevation is associated, on average, with 1.3 fewer cholera deaths per 10,000 people.Figure 1. Cholera Deaths and the Elevation of Londons Reg. Districts, 1849Figure 2. Cholera Deaths, Elevation and Water Supply of Londons Reg. Districts, 1849Water from Central LondonWater from upriverWater from Central LondonWater from upriver^OLS Fitted Line

^Water from Central LondonWater from upriver^OLS Fitted Line

^52.136Two CampsMiasmatists (M)Foul Air (FA)2. Contagionists (C)Contaminated Water (CW)

The data available after the 1948-1949 Cholera epidemic was incapable of resolving the debate. To measure the effects of good or bad water supply, it is requisite to find two classes of inhabitants living at the same level [Elevation] but differing in [the water one drinks] But of such experimenta crucis [sic] the circumstances of London do not admit. William Farr (Ghost Map, p. 102)Tuesday, September 5ALL SMELL IS DISEASEEDWIN CHADWICKThe first solid cause for home began to filter through the neighborhood Tuesday morning. For the first time in four days, Henry Whitehead let himself believe that this terrible visitation might finally be passing. The wife of Mr. G, the tailor, had died that morning, but for every new death, Whitehead could point to another dramatic recovery. The servant woman he had been tending to since Friday had risen from what she had assumed would be her deathbed, her pallor much improved. Two adolescentsa boy and girlhad also turned the corner, much to the delight of their remaining family. All three of them attributed their recovery to one thing: they had consumed large quantities of water from the Broad Street pump since falling ill. The speed and intensity of their recovery made an impression on Whitehead that would linger in his mind through the coming weeks.

b) The Exemption Proves the Rule2. Broad Street PumpEvidence that Cholera was waterborne from the 1854 Cholera EpidemicDistance from the Broad Street PumpCholera Cases per 10,000 residents

Snow knew that the case would be made in the exceptions to the rule. (The Ghost Map, p. 140) Pockets of life where you would expect deathpockets of death where you would expect life.Distance from the Broad Street PumpCholera Cases per 10,000 residents

Pockets of life where you would expect deathpockets of death where you would expect life.Pockets of life where you would expect deathpockets of death where you would expect life.Distance from Broad Street Pump (miles)Cholera Cases per 10,000 residents

Pockets of life where you would expect deathpockets of death where you would expect life.Pockets of life where you would expect deathpockets of death where you would expect life.St. James Workhouse93 deaths per 10,000 residents (5/535) because water supplied by Grand Junction Waterworks Susannah Eley93 deaths per 10,000 residents (5/535) because water supplied by Grand Junction Waterworks Lion Breweryno deaths among 70 workers because private pipeline and beer drinkers

5 deathsno deathsEley Brothers Factory18 deathsEley FactoryWork HouseBrewery 1 2

Susannah lived in HempsteadEvidence that Cholera was waterborne from the 1854 Cholera Epidemic1. John Snows Grand ExperimentWas it a natural experiment or a difference-in-difference analysis? London was without cholera from the latter part of 1849 to August 1853. During this interval an important change had taken place in the water supply of several of the south districts of London. The Lambeth Company removed their water works, in 1852, from [the heart of London] to [upriver]; thus obtaining a supply of water quite free from the sewage of London (Snow, On the Mode of Communication of Cholera, 1855, p. 68).

John Snow

Battersea BridgeNThe Thames runs from West to EastSouthwark BridgeLondon Bridge

moved1845

Moved in 1852Seething Wells IntakeSeething Wells was beyond the tidal reach of the ThamesSouthwark & Vauxhall Water Company (S&V)Lambeth WaterworksThe experiment ...was on the grandest scale. No fewer than three hundred thousand people of both sexes, of every age and occupation, and of every rank and station, from gentle folks down to the very poor, were divided into two groups without their choice, and, in most cases, without their knowledge; one group being supplied with water containing the sewage of London [S&V], and the other group having water quite free from such impurity [Lambeth Company] 31 subdistricts12 served by S&V only 3 served by Lambeth onlyNot random100 cholera cases per 10,000 residents 0 casesrelatively well-to-do suburbssmog-bound industrial zones 16 served by both companies random via natural experimentpipespromiscuously interlinked householdsassigned w/o knowledgeS&V householdsLambeth households315 cases per 10,000 residents37 cases per 10,000 residentsSame income & elevation Table. Cholera Deaths in 16 Sub-Districts Served by 2 Water Companies, 1854HouseholdsDeaths(#)(#)(# per 10,000)S&V (intake in heart of London)40,0461,263315Lambeth (intake upriver)26,1079837Rest of London256,4231,42259In 1849 when cholera was last present in London, mortality due to cholera was similar among persons supplied by the Lambeth Company and the Southwark and Vauxhall Company.Epidemiologist Ralph Frerichs 1849 1852 1854Lambeth moved its intake pipe from downriver to upriver. 37Deaths per 10,000 households 315If the subdistricts that Lambeth served exclusively were relatively well-to-do suburbs then it seems plausible that it might have served relatively well-off households in the areas served by both companies (i.e., the households on the border) Increased risk due to foul water:A

BCDNatural experimentA BDifference-in-difference1849 epidemic was more severe(A B) (C D) Validity rests on assignment within the natural experiment being truly randomControls for the potential non-randomness The DD idea was probably pioneered by physician John Snow (1855), who studied cholera epidemics in London in the mid-nineteenth century.

Friday, September 8THE PUMP HANDLEDEATHS DISPENSARYOn Thursday night, the Board of Governors of St. James Parish had held an emergency meeting to discuss the ongoing outbreak and the neighborhoods response.

Halfway into the meeting, they received notice that a gentleman wished to address them. It was John Snow, armed with his survey of the past weeks devastation. He stood before them, and in his odd, husky voice told them that he knew the cause of the outbreak, and could prove convincingly that the great majority of cases in the neighborhood could be traced to its original source. It is unlikely that Snow went into the intricacies of his broader case against the miasma theorybetter to go straight to the telling patterns of death and life, leave the philosophizing for another day. He explained the dismal ratios of survival