What are the different categories of …

• Infectious and non-infectious causes:

One of the causes of diseases is the infectious agents, mostly called microbes or micro-organisms. Diseases where microbes are the immediate causes are called infectious diseases. This is because they spread the diseases in the community.

Some diseases 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. Such diseases are called non-infectious diseases. For example, cancer is caused by genetic abnormalities. High blood pressure can be caused by excessive weight and lack of exercise. Different diseases spread by different means and can be treated and prevented at community level.

• Infectious diseases:

• Infectious agents:

Organisms that can cause disease are found in a wide range of such categories. Some of them are viruses, bacteria, fungi, protozoans or multicellular organisms, such as worms.