Among the world’s poor people diarrhoea is a killer. Up to 500,000 children are thought to die every year from enteric diseases, such as cholera and dysentery. Repeated infections also weaken them, laying them open to attack from other killers such as pneumonia. Diarrhoea can affect a person’s size and shape. Indian children are often shorter than sub-Saharan African children from families of similar incomes, partly because they fall sick more often.
In Bangladesh deaths from diarrhoea and other enteric diseases have fallen by 90% in the past two decades. In 1990 the under-five death rate in Bangladesh was 54% higher than the world average; now it is 16% lower. In a school in Trishal, northern Bangladesh, the headmaster has noticed some changes in his pupils during his 27-year tenure. Children miss fewer lessons because of illness, there have been no outbreaks of cholera in the past ten years, and he thinks that pupils are taller than they used to be. In 1993–94, 14% of Bangladeshi babies aged between 6 and 11 months had suffered an attack of diarrhoea in the previous two weeks. That is an important stage in a child’s development, but also a period of great vulnerability to stomach bugs, as babies are weaned. By 2004 the proportion of stricken babies had fallen to 12%, and in 2014 it had dropped below 7%. Stunting (being extremely short for one’s age) has declined in a similar way. In Matlab, a part of Bangladesh with good data, deaths from diarrhoea and dysentery have dropped by about 90% since the early 1990s.
There are a number of lessons to be learnt. The first is that cheap, simple, imperfect solutions are often good enough. What matters is having lots of water pumps and lots of toilets. The more convenient they are, the more people will use them. The most obvious explanation for Bangladesh’s success is the proliferation of outhouses in Trishal and other villages. Made of tin or palm fronds, these conceal simple pit latrines. A household toilet is now a symbol of respectability, to the extent that marriages have been called off when a groom’s family is discovered not to have one. Two-thirds of the latrines built between 2006 and 2015 were constructed not by charities or the government, but by ordinary people. Bangladesh has targeted poor people – as rich are more likely to afford to construct improved sanitation.
A second lesson is that human behaviour is just as important. Bangladesh’s government and charities have built latrines, too, but they have worked harder to stigmatise open defecation. Nevertheless, about 5% of households still resort to woods or roadsides, or use toilets overhanging rivers. But Bangladesh has certainly done better than other poor countries. According to the WHO, 40% of Indians defecate outdoors.
Third, clean water is vital to reducing illness. The village of Trishal has an abundance of drinking water 33 pumps for 270 households. The great majority were paid for privately. The water pumps are very close to the outhouses, but this might not matter, as bugs can barely travel more than two metres underground.
Whereas groundwater is pretty clean, the water that comes out of pumps is not. If Bangladeshis can be persuaded to wash water pumps, pots and their hands, and to reheat food that has been allowed to cool down, all as a matter of routine, rates of enteric disease ought to decline even further. The simplest message is about the importance of basic hygiene. Bacteria often live on people’s hands, and multiply on food.
Thus, it is possible to achieve impressive progress in term of reduction of morbidity and mortality with improvements in sanitation and water supply. By targeting poorer communities, the evidence suggests that richer ones will not want to be left behind.