Guest post by Arwen Cross
“Cholera is frightened of a collar and tie” is an old saying in Mozambique, explains Jim Black. It’s not the dress-code that’s important, but the wealth it represents. Cholera, like other deadly forms of diarrhoea, is a poor man’s disease. Wealthier people have better living standards which include access to clean water and sanitation – the keys to avoiding diarrhoea. “I guess the moral of the story is to make people rich so they won’t get cholera anymore,” jokes Michael Emch. But since poverty is a difficult problem to solve, scientists are working out other ways to prevent this deadly disease.
The impact of cholera
Cholera kills 50% of untreated patients, but it’s not the only type of deadly diarrhoea. The World Health Organisation estimates that diarrhoea kills 1∙4 million children under five every year. Most of these children live in the developing world and many do not have access to basic sanitation and clean drinking water.
Even if people have clean drinking water, diarrhoea spreads if there’s not enough water available for washing. In 1985 cholera broke out at a refugee camp in Sudan even though chlorinated water was provided. There simply wasn’t enough water, according to Associate Professor Jim Black an epidemiologist from the University of Melbourne. “In a hot dry environment like the Northeast of Sudan, five litres per person per day is only just enough for cooking and drinking, and so basically no-one had enough water to wash anything,” he said.
In hospital cholera patients are treated by rehydration, and only 1% of treated cholera patients die of the disease. But treatment only helps one infected patient at a time. Working in Mozambique, Black tried to provide prevention as well. This involved chlorinating drinking water and sending “a kind of flying squad” into cholera patients’ homes that used bleach as a disinfectant. They also encouraged people “to wash all the clothes and bedding and anything that might have been contaminated as the person got sick.”
A good vaccine would be a very effective way to prevent cholera. Professor Michael Emch of the University of North Carolina used spatial epidemiology, or mapping of disease outbreaks, to study a vaccine trial in the town of Matlab in Bangladesh. The vaccine was initially thought to be only 50% effective. But Emch’s research, published in the International Journal of Epidemiology, found that the vaccine was 75% effective in some areas.
Emch’s maps showed that the vaccine was effective in some neighbourhoods and not others. Places where more people had agreed to join the vaccine trial had less cholera. This happened because of what is described as the ‘herd effect’. This means that in a community where most people are vaccinated, a small number of unvaccinated people will be protected.
Emch tested to see if the new vaccine offered protection through the herd effect. Children under two years couldn’t be vaccinated in the trial. But since cholera is a childhood disease, Emch wanted to see if the herd effect protected them. He found that babies were less likely to get sick if the adult women in their household had been vaccinated.
“We think that this cholera vaccine should be used in endemic settings,” concluded Emch, describing places where cholera is common. In Matlab, cholera is certainly endemic – there’s an outbreak about three times each year. Emch’s maps of Matlab neighbourhoods have revealed that
the new vaccine could save lives there.
Vaccines can only target one disease at a time, so Peter Dwan, head of international programs at the charity WaterAid, focuses on stopping the spread of disease. “The way that you get diarrhoea is through ingesting an infectious dose of pathogens, which mostly exist in infected human faeces,” explains Dwan. This is called the faecal-oral route of infection.
In practice, breaking the faecal-oral route of infection can be very simple. People need clean drinking water and toilets with lids to keep flies out. They also need to know that washing their hands is important and have good access to water. According to Dwan, “The more time that a family would spend collecting water, the less water they’re likely to use”. If a family has to walk half an hour to collect water, then it becomes difficult to carry enough home. After cooking, drinking and clothes washing, hand washing can become a low priority.
Dwan finds that people have traditions that protect drinking water, and aims to enhance these practices with a combination of infrastructure (basic toilets, wells and taps) and education. “You’ve got your science and then,” Dwan explains, “you’ve got people’s traditional practices, and you want to move these things closer together. It’s about how you interact with people that might lead to them making some of those changes for themselves.”
Millennium Development Goals
Getting water and toilets to everyone in the world is expected to take years. As part of its Millenium Development Goals the UN aims to halve, by 2015, the proportion of people without sustainable access to safe drinking water and sanitation. While we are on track to reaching the safe drinking water goal, basic sanitation is unlikely to reach its target.
Why can the world solve the problem of water supply but not toilets? Because it’s not a glamourous problem to solve. “Any politician would be happy to get up and give a speech in the parliament about water because it’s kind of clean and positive and uplifting. But to get up and give a talk about sanitation and toilets; it’s actually a backwards career step for a politician,” Black says. “It’s the kind of thing that people tend to sweep under the carpet, they don’t really want to talk about it”.
Frightening cholera out of the world might take more than a collar and tie. Water, sanitation, hygiene and vaccines are all parts of the solution. But if the UN sanitation goal is going to be met, we’re going to have to talk about toilets.
Arwen Cross won second prize in the New Scientist Prize for Science Writing for this article in 2011.