Diarrhoeal Disease

Why is diarrhoeal disease important?

In the United Kingdom we primarily think of diarrhoea as an inconvenience, the main cost associated with lost productivity caused by parents taking time off work to care for ill children. Today, elsewhere in the world, diarrhoea kills over 800,000 children under-five a year. Diarrhoeal disease is also an important underlying cause of malnutrition and pneumonia, the former weakening a child’s ability to fight diarrhoea and other diseases, the latter the leading cause of child deaths globally.

Diarrhoeal diseases are easily preventable by WASH – water, sanitation and hygiene, yet in 2010, 2.5 billion people still lacked access to improved sanitation, and almost 800 million lacked access to safe drinking water. The burden of disease and the majority of our work is concentrated in sub-Saharan Africa and South Asia where coverage of water and sanitation are lowest and where the greatest gains in child health can be made.

Our key contributions and research in this area:

Researchinto diarrhoeal diseases covers almost everything that the Environmental Health Group has worked on because diarrhoeal diseases are impacted by most of the work we do in water, sanitation and hygiene. Below a few examples of out landmark contributions to the field over the years:

Development of the Bradley Classification of water-related diseases

In the 1970s, Sir David Bradley and colleagues created the well-known and widely used classification of water-related diseases, grouping diseases by transmission route into four categories:

  1. Water-borne diseases related to water quality e.g. pathogens transmitted in contaminated water such as cholera;
  2. Water-washed diseases that result from insufficient water available for personal hygiene, e.g. ongoing transmission of cholera after an initial outbreak, or endemic transmission of diarrhoea;
  3. Water-based diseases which result from a pathogen transmitted via a host in the water such as schistosomiasis
  4. Water-related diseases such as malaria, which is transmitted by mosquitoes that breed in water.

Before this classification was developed diseases were commonly grouped by disease agent e.g. bacteria, viruses. Grouping diseases by their mode of transmission was immensely useful for those considering how to interrupt transmission. This is particularly relevant for diarrhoeal diseases, which can be spread by a number of different routes.

Contribution to evidence-base for health impact of WASH interventionshandwashing plos

Dr. Val Curtis and Professor Sandy Cairncross from the Environmental Health Group conducted a systematic review of interventions that measured the impact of handwashing with soap interventions on diarrhoea. Their 2003 review found that washing hands with soap can reduce risk of diarrhoea by 42-47%, prompting many to call hygiene promotion one of the most cost-effective public health interventions available.

Guidance for public health practitioners working in WASHengineering in the tropics

Numerous text books have been developed by members of the Environmental Health Group over the years. One that is particularly useful for people working in WASH is the Cairncross & Feachem 1993 book, “Environmental Health Engineering in the Tropics”.

Development of methods to measure diarrhoea outcomes

The success of WASH interventions is often measured based on the impact of the intervention on risk of diarrhoea. However, measuring diarrhoea is challenging: for example, people are often required to report on whether or not they have had diarrhoea. One issue with this is that repeated surveillance visits are often made to households and people grow weary of these visits and change the way they answer questions to get rid of the investigator. Researchers in our group have investigated different ways of measuring diarrhoea.

Our current projects in this area:

As diarrhoeal diseases can be transmitted by so many different routes (water, food, hands, flies etc.), most of the work of the Environmental Health Group impacts diarrhoeal diseases to some extent.

Recently we have been working on cluster-randomised trials to measure health outcomes (including diarrhoea) and/or to measure behaviours that should reduce risk of diarrhoea.

Water: We are currently planning a cluster randomised trial which will look into the health impacts of a programme delivering free water filters and improved cook stoves in Rwanda.

Sanitation: We are currently running a cluster-randomised controlled trial of a sanitation intervention in Orissa, India. Data are currently being analysed to look at the impact of building latrines on diarrhoea and other outcomes.


More about this study can be found on our sanitation page or in the some of the related publications below.

Hygiene: Another cluster-randomised controlled trial is being conducted into handwashing in Andhra Pradesh, India. Findings show that a community-based handwashing promotion programme targeted to rural villages was able to sustain improved handwashing practices over a 12 month period. As handwashing with soap can reduce risk of diarrhoea, improving handwashing behaviour could well have reduced diarrhoea incidence  in the study villages.

superamma results

More information about this trial is available here or on the Superamma website.

A selected list of the EHG’s key publications related to diarrhoeal disease:


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