Waterborne diseases are caused by pathogenic microorganisms that most commonly are transmitted
in contaminated fresh water. Infection commonly results during bathing, washing, drinking,
in the preparation of food, or the consumption of food thus infected. Various forms of waterborne
diarrheal disease probably are the most prominent examples, and affect mainly children in developing
countries; according to the World Health Organization, such diseases account for an estimated 4.1%
of the total DALY global burden of disease, and cause about 1.8 million human deaths annually.
The World Health Organization estimates that 88% of that burden is attributable to unsafe
water supply, sanitation and hygiene.
Overview The term "waterborne disease" is reserved
largely for infections that predominantly are transmitted through contact with or consumption
of infected water. Trivially, many infections may be transmitted by microbes or parasites
that accidentally, possibly as a result of exceptional circumstances, have entered the
water, but the fact that there might be an occasional freak infection need not mean that
it is useful to categorise the resulting disease as "waterborne". Nor is it common practice
to refer to diseases such as malaria as "waterborne" just because mosquitoes have aquatic phases
in their life cycles, or because treating the water they inhabit happens to be an effective
strategy in control of the mosquitoes that are the vectors.
Microorganisms causing diseases that characteristically are waterborne prominently include protozoa
and bacteria, many of which are intestinal parasites, or invade the tissues or circulatory
system through walls of the digestive tract. Various other waterborne diseases are caused
by viruses. Yet other important classes of water-borne
diseases are caused by metazoan parasites. Typical examples include certain Nematoda,
that is to say "roundworms". As an example of water-borne Nematode infections, one important
waterborne nematodal disease is Dracunculiasis. It is acquired by swallowing water in which
certain copepoda occur that act as vectors for the Nematoda. Anyone swallowing a copepod
that happens to be infected with Nematode larvae in the genus Dracunculus, becomes liable
to infection. The larvae cause guinea worm disease.
Another class of waterborne metazoan pathogens are certain members of the Schistosomatidae,
a family of blood flukes. They usually infect victims that make skin contact with the water.
Blood flukes are pathogens that cause Schistosomiasis of various forms, more or less seriously affecting
hundreds of millions of people world-wide. Long before modern studies had established
the germ theory of disease, or any advanced understanding of the nature of water as a
vehicle for transmitting disease, traditional beliefs had cautioned against the consumption
of water, rather favouring processed beverages such as beer, wine and tea. For example, in
the camel caravans that crossed Central Asia along the Silk Road, the explorer Owen Lattimore
noted, "The reason we drank so much tea was because of the bad water. Water alone, unboiled,
is never drunk. There is a superstition that it causes blisters on the feet."
Protozoal infections Parasitic infections
Bacterial infections
Viral infections
Socioeconomic impact Waterborne diseases can have a significant
impact on the economy, locally as well as internationally. People who are infected by
a waterborne disease are usually confronted with related costs and not seldom with a huge
financial burden. This is especially the case in less developed countries. The financial
losses are mostly caused by e.g. costs for medical treatment and medication, costs for
transport, special food, and by the loss of manpower. Many families must even sell their
land to pay for treatment in a proper hospital. On average, a family spends about 10% of the
monthly households income per person infected. See also
airborne disease Food Microbiology
Free-living amebic infection Milorganite
Portable water purification Public health
Swimming pool sanitation Vector
Water pollution Water quality
Water resources Water scarcity in Africa
Water supply Zoonosis
References
Academic resources Journal of Water and Health. ISSN 1477-8920.
External links American-MC Water Sampling Stations for U.S.
Centers for Disease Control and Prevention Waterborne Disease Information
Drastic consequences of diarrhoeal diseases ICS 91.140.60 Water supply systems - A series
of the ISO standards World Health Organization
Water-related Diseases, Contaminants, and Injuries Listing of water-related diseases,
contaminants and injuries with alphabetical index, listing by type of disease and listing
by symptoms caused including links to other resources
Center for Diseases Control U.S. Ratings of water safety worldwide
Genome information on Shigella and Salmonella is available at the NIAID PathoSystems Resource
Integration Center