Why everyone should know about solar disinfection
The advantage of living and working in Oxford is you don’t have to travel far to meet interesting people, particularly in the field of epidemiology. Last week, I met with Mike Clarke, Director of the UK Cochrane Centre, and our wide ranging discussion turned to the recent release of the Cochrane Evidence Aid: resources for Haiti earthquake.
I have always thought release of materials in this way is more of a publicity stunt than a useful resource. This time I couldn’t have been more wrong. Indeed, I can’t believe I’ve never heard of solar disinfection. When I mention this to colleagues, most have never heard of it either, and if you have, then you are definitely in the minority.
So what is solar disinfection and what is it good for? It is simply disinfection by heat, either by boiling or pasteurization) and the use of ultraviolet radiation, either using the sun (solar disinfection) or by using an artificial ultraviolet light lamp. The evidence for its effects comes from a systematic review of Interventions to improve water quality for preventing diarrhoea.
In two trials of solar disinfection in this review both intervention and control households received plastic bottles for storing their drinking water. The intervention group was instructed to place the bottles on roofs to expose them to the sun, while control groups were told to keep the filled bottles indoors. Solar disinfection was statistically significantly better than the control for reducing diarrhoea episodes in people of all ages. For diarrhoea the odds ratio odds ratio for prevention was 0.69 95 % confidence interval 0.63 to 0.74 basically a 30 percent reduction in diarrhoea. In addition since controls also received bottles this may have provided some protection against diarrhoea by means of improved storage, thus underestimating the true effect.
Knowing about solar disinfection, and implementing it, is great Evidence-Based Medicine. From now on I will view evidence aid resources from the Cochrane Library in a different light.
Diarrhoea-a neglected cause of child mortality
This week, the Lancet released two articles in its “Online First” section, both concerned with the second leading global cause of infant death: diarrhoea. A staggering one in every five child deaths—around 1•5 million a year —is due to diarrhoea, which kills more children than AIDS, malaria, and measles combined. I have previously blogged about the Zimbabwean cholera crisis and the tragedy of the long-established, but poorly translated treatments for diarrhoea. The first article draws attention to a new UNICEF report: “Diarrhoea: why children are still dying and what can be done”, and suggests a seven-point plan for diarrhoea control:
- Rotavirus and measles vaccinations
- Promotion of early and exclusive breastfeeding and vitamin A supplementation
- Promotion of handwashing with soap
- Improve water quantity and quality, including treatment and safe storage of household water
- Promotion of community-wide sanitation
- Fluid replacement to prevent dehydration
- Zinc supplements
The authors find that only 39% of children with diarrhoea in developing countries are receiving these simple, cheap interventions.
The other, more hopeful Lancet article concerns a trial of a new cholera vaccine in more than 65 000 individuals, including children older than 1 year, living in an urban slum in India. Clusters of households were either allocated two doses of the vaccine or the placebo. At 2 years, the vaccine did not have any more side effects than the placebo and was 67% effective in protecting against cholera in the entire population. The vaccine was 49% protective against cholera in children aged 1—5 years, although its effectiveness dropped if the vaccine was not given in two doses. This vaccine is both effective and affordable, giving it great potential for mass immunisation programmes in cholera-endemic areas.