The World Health Organization (WHO) is a specialized agency of the United Nations that is concerned with international public health. It was established on 7 April 1948, and is headquartered in Geneva, Switzerland. The WHO is a member of the United Nations Development Group. Its predecessor, the Health Organization, was an agency of the League of Nations.
The constitution of the World Health Organization had been signed by 63 countries on 7 April 1948, with the first meeting of the World Health Assembly finishing on 24 July 1948. (source: en.wikipedia.org/wiki/World_Health_Organization)