Answer: When pathogens enter and multiply in body tissues
Explanation:
Disease enter our body system, when several pathogens like viruses, bacteria, or other microbes enter our body system and start to produce or multiply. Bacteria sometimes, produce so rapidly or speedily on the host tissues and disrupt normal body function. Pathogens kills or destroy the cells and tissues when they enter the body system. Pathogens usually enter the human body system by two main types of routes: mucosal surfaces within the body which includes, the linings of the respiratory, digestive, reproductive, or urinary tracts and the epithelial surfaces on the outside of the body which includes, areas of skin that are either undamaged or compromised due to insect bites, cuts or scrapes.
When pathogen penetrates the host defenses, infection occurs in the host. Infection is a disease of the body that is caused by invasion and multiplication of pathogens (infectious biological agents that causes diseases or illnesses to the host) such as bacteria, viruses, parasites and so on normally not found with the body. They can easily spread from their point of origin if not contained due to the multiplicability of the pathogens causing it.
