Waterborne diseases are any illness caused by drinking water contaminated by human or animal faeces, which contain pathogenic microorganisms. Contaminated drinking water, used in the preparation of food can be the source of food borne disease through consumption of the same microorganisms.
According to the WHO, diarrheal disease accounts for an estimated 4.1% of the total Disability Adjusted Life Years (DALY) global burden of disease and is responsible for the deaths of 1.8 million people every year. It was estimated that 88% of that burden is attributable to unsafe water supply, sanitation and hygiene, and is mostly concentrated in children in developing countries.
Transmission:
Water borne diseases spread by contamination of drinking water systems with the urine and faeces of infected animal or people.
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This is likely to occur where public and private drinking water systems get their water from surface waters (rain, creeks, rivers, lakes etc.), which can be contaminated by infected animals or people. Run-off from landfills, septic fields, sewer pipes, residential or industrial developments can also sometimes contaminate surface water.
This has been the cause of many dramatic outbreaks of faecal-oral diseases such as cholera and typhoid. However, there are many other ways in which faecal material can reach the mouth, for instance on the hands or on contaminated food.
In general, contaminated food is the single most common way in which people become infected. Waterborne disease can be caused by protozoa, viruses, bacteria and intestinal parasites.
Dimension of the Problem:
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In developing countries four-fifths of all the illnesses are caused by water-borne diseases, with diarorhea being the leading cause of childhood death.
The global picture of water and health has a strong local dimension with some 1.1 billion people still lacking access to improved drinking water sources and some 2.4 billion to adequate sanitation.
Today we have strong evidence that water-, sanitation and hygiene-related diseases account for some 2,213,000 deaths annually and an annual loss of 82,196,000 Disability Adjusted Life Years (DALYs) (R. Bos, Dec. 2004).
WHO estimates indicate that worldwide over 2 billion people are infected with schistosomes and soil transmitted helminthes and 300 million of these suffer serious illness as a result.
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Malaria kills over a million people every year, and a large percentage of them are under five as well, mainly in Africa South of the Sahara. As one of the major public health problems in tropical countries, it has been claimed that malaria has reduced economic growth in African countries by 1.3% each year over the past 30 years.
In Bangladesh alone, some 35 million people are exposed, on a daily basis, to elevated levels of arsenic in their drinking water, which will ultimately threaten their health and shorten their life expectancy.
| Diseases | Responsible Pathogen | Route of exposure | Mode of Transmission |
| Cholera | Vibrio cholerae bacteria | gastro-intestinal | often waterborne |
| Botulism | Clostridium botulinum bacteria | gastro-intestinal | food/water borne; can grow in food |
| Typhoid | Salmonella typhi bacteria | gastro-intestinal | water/food borne |
| Hepatitis A | Hepatitis A virus | gastro-intestinal | water /food borne |
| Dysentery | Shigella dysenteriae bacteria or Entamoeba histolytica amoeba | gastro-intestinal | food/water |
| Cryptosporid iosis | Cryptosporidium parvum protozoa | gastro-intestinal | water borne; resists chlorine |
| Polio | Polio viruses | gastro-intestinal | exposure to untreated sewage; may also be waterborne |
| Giardia | Giardia lamblia protozoa | gastro-intestinal | water borne |
After the Tsunami attack in Asia on Sunday the 26th of December 2004 people faced the threat of water borne diseases linked to flooding, like Shigellosis, Cholera, Hepatitis A, Leptospirosis, Typhoid Fever, Malaria and Dengue fever.
Prevention:
Clean water is a pre-requisite for reducing the spread of waterborne diseases. It is well recognized that the prevalence of waterborne diseases can be greatly reduced by provision of clean drinking water and safe disposal of faeces.
Water is disinfected to kill any pathogens that may be present in the water supply and to prevent them from growing again in the distribution systems. Disinfection is then used to prevent the growth of pathogenic organisms and to protect public health and the choice of the disinfect depends upon the individual water quality and water supply system.
Without disinfection, the risk from waterborne disease is increased. The two most common methods to kill micro organisms in the water supply are: oxidation with chemicals such as chlorine, chlorine dioxide or ozone, and irradiation with ultraviolet (UV) radiation.