Diseases and immunity
There are four main types of disease:
1. Infectious diseases
2. Deficiency diseases
3. Genetic diseases (hereditary and non-hereditary)
4. Physiological diseases
Infectious diseases are caused by pathogens – microorganisms that enter the body and then reproduce.
They can easily be spread through direct or indirect contact.
Infectious diseases are easily spread: imagine easily spreading a disease just like you spread butter on bread with knife.
Examples of infectious diseases
Typhoid, smallpox, cholera, diphtheria, influenza (flu), measles, common cold.
Measles is an example of a viral disease.