Disease has been defined as any condition that results in the dysfunction of a body part or system. There are four main types of disease: infectious, deficiency, metabolic and neoplastic.
Infectious diseases are caused by microorganisms such as viruses, bacteria, fungi or parasites. They can be spread through direct contact with an infected individual, through contaminated food or water, or via insects or other animals. Common infectious diseases include influenza, tuberculosis and malaria.
Deficiency diseases occur when the body does not receive sufficient nutrients from the diet. This can be due to poverty, poor dietary choices or an underlying medical condition such as celiac disease. Common deficiency diseases include iron-deficiency anaemia and scurvy.
Metabolic diseases are caused by errors in metabolism – the process by which the body converts food into energy. These errors can be inherited or acquired during life. Common metabolic diseases include diabetes and gout.
Neoplastic diseases are characterised by the abnormal growth of cells in the body. They can be benign (non-cancerous) or malignant (cancerous). Common neoplastic diseases include breast cancer and lung cancer.