The disease causing microbes are called pathogens. Pathogens often enter a human body by means of air, water and food. When the infectious person coughs or sneezes, the pathogens released into the air from the infectious person, enters the body of a healthy human causing diseases to him. Also, these pathogens are more often spread by the insects like female anopheles mosquito and housefly. When the same mosquito bites an infectious person and a healthy person, the pathogens are transmitted or when a housefly sitting on a garbage, sits on the food items, it transmits the pathogens through the food.