The World Health Organization (WHO) is a specialized agency under the United Nations with its headquarters in Geneva, Switzerland. Only sovereign countries can participate, and it is the largest intergovernmental health organization in the world. The purpose of the World Health Organization is to enable people all over the world to achieve the highest possible health level. The main functions of the World Health Organization include: promoting the prevention and treatment of epidemic and endemic diseases; To provide and improve teaching and training in public health, disease treatment and related affairs; Promote the determination of international standards for biological products.