WHO is the first global health organization. It replaced or absorbed many regional and national health bodies.
In the latter half of the 19th century, after several severe cholera epidemics, a series of international sanitary conferences were held in Europe to coordinate policy and practice around quarantine and disease management. The League of Nations established a health organization in 1920, and there were regional bodies as well. But the establishment of the United Nations in 1945 marked a period of aggressive internationalism and international organization-building, and though health was not initially thought to be under the U.N.'s purview, a motion by the Brazilian and Chinese delegates to establish an international health organization was unanimously accepted. A group of health experts who were working on emergency relief in the wake of World War II were charged with the task of drafting a constitution to define the structure and mandate of the body that would become known as the World Health Organization.
The work of WHO is mainly carried out by a secretariat; secretariat staff are led by a director-general and work in areas identified by an executive board and ratified by an assembly.
The secretariat consists of thousands of health and other experts and support staff who work at headquarters, regional offices, and in member countries around the world. At the top of this bureaucracy is the director-general, who is elected for a five-year term. A new director-general, Dr. Jong-Wok Lee, was nominated by the executive board and elected by the assembly in May 2003. This native of South Korea was trained as a medical doctor in Seoul and completed a Masters of Public Health in Hawaii. He worked for WHO for 19 years before being elected to his current post.