On March 22, 1949 Costa Rica ratified the constitution of the World Health Organization and on April 13 WHO was joined by Honduras, thus bringing the membership of the organization to 61.

The agreement by which the Pan American Sanitary Organization became the regional office for WHO in the western hemisphere was signed on May 24, 1949 in Washington by Dr. Brock Chisholm, Director General of WHO and Dr. Fred L. Soper, Director of the Pan American Sanitary Office. Under the agreement the office was to adopt and promote health and sanitary conventions and programs in the western hemisphere provided they were “compatible with the policy and programs of the World Health Organization and are separately financed.”