As we have seen, it is important to keep public health and community health factors in mind when we think about causes of diseases. We
can take that approach a little further. It is useful to think of the immediate causes of disease as belonging to two distinct types. One
group of causes is the infectious agents, mostly microbes or micro-organisms.
Diseases where microbes are the immediate causes are called infectious diseases. This is because the microbes can spread in the community, and the diseases they cause will spread with them.
On the other hand, there are also diseases that are not caused by infectious agents. Their causes vary, but they are not external causes like microbes that can spread in the community. Instead, these are mostly internal, non-infectious causes.
For example, some cancers are caused by genetic abnormalities. High blood pressure can be caused by excessive weight and lack of exercise. Similarly, diabetes is not infectious. You can think of many other diseases where the immediate causes will not be infectious.
The ways in which diseases spread, and the ways in which they can be treated and prevented at the community level would be different for different diseases. This would depend a lot on whether the immediate causes are infectious or non-infectious.