Pathogens

The conditions in your body like your temperature help harmful bacteria that enter your body grow and multiply. Bacteria can slow down the normal growth and metabolic activities of the body's cells and tissue. Some kinds of bacteria produce toxins that can kill cells on contact.

Viruses infect and multiply in the host cells. The host cells die when viruses break out of the host cells. The new viruses infect other cells, which leads to the destruction of tissue.

According to Koch's Rule, most diseases caused by pathogens can be treated with medicines. Today, we still use the method Robert Koch developed in the early 19th century to identify organisms.