Certan disease causing organisms are spread by drinking contaminated water. Thus these water borne pathogens enter their new host through his mouth . They often affect intestine of their host causing diarrhoea. They leave the body of their host via his faeces. In place where sanitation and personal hygiene are poor drinking water can easily become contaminated by such infected body wastes . Disease like typhoid and cholera are cause mainly by water borne pathogens.
Some people can Harbour pathogenic organisms in their bodies without showing any sign of disease . These people are known as carriers.