The World Health Organization (WHO) is a specialized agency of the United Nations. Its headquarters is located in Geneva, Switzerland. Only sovereign countries can participate. It is the largest intergovernmental health organization in the world. The purpose of the World Health Organization is to enable people around the world to achieve the highest possible level of health. The main functions of the World Health Organization include: promoting the prevention and treatment of epidemics and endemic diseases; providing and improving the teaching and training of public health, disease care and related matters; and promoting the establishment of international standards for biological products.