A communicable disease is caused by a pathogen and can be passed from one organism to another. Pathogens are microorganisms such as viruses, bacteria, protists and fungi. Measles is caused by a virus, tuberculosis by bacteria, and malaria by a protist.
A non-communicable disease cannot be passed on and is not caused by a pathogen. Examples are cancer, heart disease, type 2 diabetes and asthma. Cancer is not caught from another person.
Some non-communicable diseases are inherited. Cystic fibrosis is inherited from parents through genes, not caught. Others are linked to lifestyle, such as smoking, diet and lack of exercise, or to the environment.