Basic principles of disease occurrence

Answer 1

In general health terms, the basic principles of disease-occurrence include the following: First, there must be an active disease-agent of some kind present in or near an organism that is subject to its operation. Second, the organism must be in a receptive state to the disease-agent, that is, must be penetrable in some manner by the disease-agent. Third, upon penetration of the host-organism, the disease-agent must be strong enough (whether in respect to internal potency, ineffective host-organism defenses, or absence of host-organism defenses) to plant and grow within the host-organism.