Infection and immunity
Infection and immunity

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Infection and immunity

3.8.1  Diarrhoeal diseases

Cholera, caused the by the presence of Vibrio cholerae bacteria in drinking water, is a potentially life-threatening diarrhoeal disease. The disease is widespread in many parts of the developing world, but cholera was also a major cause of death in industrialised Western countries in the 19th century as discussed in Section 2.4.

However, many other pathogenic bacteria also cause diarrhoea, particularly those transmitted in contaminated food and water. They include Salmonella in raw eggs and undercooked poultry, and pathogenic varieties of Escherichia coli [esh-err-ish-ee-ah koh-lye], mainly in red meat or raw (unpasteurised) milk, but also in unwashed fruits and vegetables contaminated with faeces. Diarrhoeal diseases are also caused by some viruses and protists.

Around 1.5 million (1 500 000) people die from diarrhoeal diseases every year, most of them young children (Figure 14). If untreated, the loss of tissue fluids and essential salts in diarrhoea rapidly results in dehydration, disruption of body chemistry, and malfunction of the nervous system and vital organs. The loss can be replaced by drinking a simple oral rehydration solution (ORS) of sugar and salt dissolved in clean water until the diarrhoea subsides. Distribution of millions of sachets of ORS powder and teaching parents how to administer it is slowly reducing the mortality from diarrhoea in childhood. In severe cases, the solution may have to be given intravenously (directly into a vein).

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Figure 14  Diarrhoeal diseases are easily transmitted wherever people lack sanitation and are a major cause of death among children aged under five years.
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