Microbes are small organisms that are present in the environment and some are capable of causing diseases in humans. They are present all around us in air, soil and water. Prior to the advent of modern water treatment involving disinfections and filtration, water-borne diseases killed thousands of people all around the world. In areas that lack modern sanitation and water treatment, water-borne diseases are still a major contributor to mortality.
Diseases caused by water-borne bacteria include cholera and typhoid.
Water-borne viral diseases include polio, hepatitis, and various gastrointestinal diseases. Water-borne protozoa that cause disease include Giardia and Cryptosporidium. These diseases usually occur as a result of inadequately treating drinking and wastewater. Everyone is at a risk for water borne disease. But infants, children, older persons and immuno-compromised people are generally at increased risk.