Human Health can be affected by drinking contaminated water through food or directly as drinking water and also by use of contaminated water for personal hygiene or recreation (swimming pools for swimming and diving and other water sports). The term water related disease include water borne disease also. Developing countries carry a heavy burden of water borne diseases due to lack of safe drinking water supply. Among the water borne and water related diseases diarrhea is most important. Water related disease can be biological (water borne disease) and chemical.
Biological: They are two types those caused by the presence of infective agents in water and those due to presence of aquatic host in water.
Due to Infective agents:
These can be subdivided by the type of the infective agent present in water-
Viral: Viral hepatitis (due to hepatitis A virus, Hepatitis E virus) poliomyelitis and rotavirus diarrhea in infants.
Bacterial: Typhoid fever, paratyphoid fever, Escherichia coli (E. coli) diarrhea, cholera, bacillary dysentery, Travelers diarrhea etc.
Protozoal: Amoebiasis (Entamoeba histolytica), giardiasis (giardia lamblia).
Helminthic: Worm infestation like round worm, thread worm and hydrated disease.
Leptospiral: Weill’s disease
Due to presence of aquatic host:
Cyclopes : guinea worm, fish tape worm.