Microorganisms do not always cause disease, and different types often live in and on people with no ill effects. Thus, in the past, microorganisms were divided into two groups:
Pathogens – microbes that cause disease
Non- pathogens – microbes that do not cause disease
However, research has shown that almost any microorganism can cause disease in some people, given the right conditions. Therefore, little distinction is made between pathogens and non- pathogens. In the following sections we’ll review the different forms of pathogens you may encounter.