In high-income countries, chronic diseases are some of the leading causes of disability and death in adults aged 65 or older. With the demographic and socio-economic transition in developing countries, causes of deaths will shift from communicable, maternal, perinatal, and nutritional causes in the younger population to chronic diseases in older people, and overall disease patterns will also change from acute infectious diseases to chronic diseases. This is known as the epidemiological transition. These chronic diseases include non-infectious diseases (such as arthritis, hypertension, cardiac insufficiency, renal insufficiency, diabetes, chronic obstructive lung disease, and cancer), mainly in the elderly, and infectious diseases (mainly HIV/AIDS) in all age categories.