Thanks to Patrick from Woodbridge School
for his thoughts responding to this problem.
Look at the
page for more links to information.
Here's what he says :
Cholera is a
bacterial disease that often kills, usually by dehydration or lack
of vital salts. It causes extreme diarrhoea and vomiting, and the
water loss from the dehydration causes the blood to turn black and
the skin blue.
The main supporting evidence for the decision is:
... 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... 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... In... other cases, the
deceased were children who went to school near the pump in Broad
... [There] were 61 instances in which... the deceased persons used
to drink the pump water from Broad Street...
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. This is strong evidence,
but the evidence cannot confirm with absolute certainty that this
is the cause - there could have been another cause unrelated to the
pump, in which case the decision would have been incorrect.