In a broader sense, it sometimes includes injuries, disabilities, disorders, syndromes, infections, isolated symptoms, deviant behaviours.
Diseases can affect people not only physically, but also emotionally, as contracting and living with a disease can alter the affected person's perspective and quality of life.
There are four main types of disease: infectious diseases, deficiency diseases, genetic diseases (both hereditary and non-hereditary), and physiological diseases. Diseases can also be classified as communicable and non-communicable. The deadliest diseases in humans include cardiovascular disease and cancers. Cardiovascular disease include hypertension, coronary artery disease (blood flow obstruction), followed by cerebrovascular disease which affects blood vessels especially arteries that supply blood to the brain, which in turn can cause a stroke, and lower respiratory infections.