Pathogens are microorganisms, such as bacteria, viruses and parasites, that are known to contribute to cause disease in humans and animals. Pathogens in water can be transmitted through ingestion, inhalation or skin contact as commonly known waterborne diseases caused by pathogens include, cholera, typhoid fever, dysentery and giardiasis. Pathogens can enter the water source through human or animal waste, agricultural runoff, and inadequate treatment of wastewater. Proper water treatment and disinfection can help reduce or remove the risk of waterborne disease transmission.