Infections related to water supply and sanitation are classified into water-related and excreta-related. Water-related infections are of four types, depending on route of transmission. Water-borne transmission of disease occurs when the pathogen is in the water drunk by persons and animals (typhoid, cholera, hepatitis, dysentery). Water-washed diseases are those whose transmission is reduced by increasing the volume of water used for hygienic purposes (gastrointestinal disease, skin and eye disease, arthropod infestations). Water-based disease involves pathogens which spend part of their life cycles in water (schistosomiasis, Guinea worm). Insect-vector diseases include malaria, yellow fever, dengue, and trypanosomiasis. An environmental classification of water-related infections includes the fecal-oral category (water-borne or water-washed), water-washed category (skin and eye infections), water-based category (pathogens penetrating skin or ingested), and water-related insect vector category. Excreta-related infections can be transmitted by infected excreta or by an excreta-related insect vector. Several key factors govern the probability that excreta-related pathogens are transmitted so that disease occurs in the host: excreted load, latency, persistence, infective dose , multiplication, and host response. Excreta-related infections are also classified as fecal-oral infections (nonbacterial), fecal-oral infections (bacterial), soil-transmitted helminths, beef and pork tapeworms, water-based helminths, and insect vectors. Control strategies for the diseases can be devised from understanding the transmission routes. Major control measures are health education, safe domestic water supply, insect control , toilet provision with proper maintenance and use, sewage treatment, and thorough cooking of food. The diseases can also be classified into Decade-related infections: (1) diarrhea and enteric fevers, the major cause of childhood disease and death, (2) polio and hepatitis A, (3) worms with no intermediate host, (Ascaris and Trichuris) (4) worms with intermediate stages in pigs and cows (tapeworms), (5) worms with aquatic intermediate stages (schistosomiasis, Guinea worm), (6) skin, eye, and louse-borne infections, and (7) transmission by insects (malaria , yellow fever, Bancroftian filariasis). (See also W89-10100) (Cassar-PTT)
; Water pollution effects; Water distribution; Sanitation; Public health; Water quality; Developing countries; Diseases; Water supply; Parasites; Infection; Viruses; Mosquitos; International Decade for Drinking Water Supply and Sanitation; Water resources development; Helminths; Insects; Human diseases; Rural areas/