Evade host defense 6. Multiplication and tissue damage 7. Leave the body and start a new infection 1. For example, rhinoviruses cannot survive outside of humans. At any point in time there are always some people infected.
Humans are the reservoir of rhinoviruses.
Many opportunistic infections are derived from normal microflora- a huge reservoir of microbes. Pathogens with a human reservoir may be eradicated by vaccination efforts. For example, the smallpox virus was maintained in a human reservoir. Worldwide vaccination efforts lead to eradication of this disease in part because smallpox cannot survive outside of humans. Some human pathogens also infect animals.