A communicable disease is one that can be passed from one organism to another. It is caused by a pathogen. The four types of pathogen are bacteria, viruses, fungi and protists. Measles, tuberculosis and malaria are all communicable diseases.
A non-communicable disease cannot be passed on from one person to another, and no pathogen causes it. Examples are cancer, coronary heart disease, asthma and type 2 diabetes. Their causes include genes, lifestyle (such as diet, smoking and exercise), and the environment. Inherited conditions such as cystic fibrosis and deficiency diseases such as scurvy, which is caused by too little vitamin C, are also non-communicable.
The test is simple. If a pathogen spreads from host to host, the disease is communicable. If it cannot be caught from someone else, it is non-communicable.