The World Health Organization (WHO) is the specialized agency of the United Nations responsible for international public health. Established through a constitution that entered into force on 7 April 1948, it coordinates international health cooperation, develops technical standards, supports national health authorities, and helps organize responses to health emergencies. Its headquarters are in Geneva, Switzerland. WHO’s constitutional objective is the attainment by all peoples of the highest possible level of health. (who.int)
Origins and constitutional mandate
WHO emerged from efforts to establish a global health institution during the creation of the United Nations after World War II. Representatives of Brazil and China proposed such an organization at the 1945 San Francisco conference. An international health conference subsequently adopted its constitution in New York on 22 July 1946, with representatives of 61 states signing it. The constitution entered into force after the required twenty-sixth ratification. The first World Health Assembly opened in Geneva on 24 June 1948; 7 April is observed annually as World Health Day. (who.int)
The constitution describes health in terms of physical, mental, and social well-being rather than simply the absence of disease. It identifies the highest attainable standard of health as a fundamental right, connecting the organization’s mandate with human rights. It also recognizes governmental responsibility for providing adequate health and social measures and emphasizes international cooperation, public participation, and access to medical knowledge. These principles give WHO a mandate extending beyond infectious-disease control to broader conditions affecting population health. (who.int)
Governance and organizational structure
WHO’s principal decision-making institution is the World Health Assembly, attended by delegations from member states. It determines organizational policies, appoints the director-general, supervises financial policies, and approves the programme budget. The Executive Board consists of 34 technically qualified members designated by states elected for three-year terms. It gives effect to Assembly decisions and policies and prepares the Assembly’s agenda. The director-general heads the organization and is appointed by the Assembly on the Board’s nomination. (who.int)
The organization operates through headquarters, regional offices, and country offices. Its six regions are Africa, the Americas, South-East Asia, Europe, the Eastern Mediterranean, and the Western Pacific. Country offices collaborate with national authorities on planning, implementing, and monitoring health programmes. This structure combines international standard-setting with regional coordination and support tailored to national health systems. (who.int)
Technical standards and health programmes
A central WHO function is developing common standards and evidence-based policy options. It supports health research, monitors health trends, and provides technical assistance to governments. Its programme areas include infectious diseases, noncommunicable diseases, mental health, and the health consequences of climate change. WHO also addresses the social determinants of health, recognizing that health outcomes depend partly on conditions outside clinical services. (who.int)
WHO maintains the International Classification of Diseases (ICD), a standardized system for recording and reporting diseases and related health conditions. The eleventh revision, ICD-11, was adopted by the World Health Assembly in May 2019 and came into effect on 1 January 2022, subject to transitional arrangements. It provides a shared framework for mortality and morbidity reporting rather than requiring every country to complete implementation simultaneously. (who.int)
The WHO Model Lists of Essential Medicines guide the development of national and institutional medicine lists. They support procurement, supply, reimbursement, and other pharmaceutical policies. WHO also works to improve access to vaccines, diagnostics, medical devices, and other health products. These activities form part of its support for universal health coverage, alongside work on primary health care, workforce development, sustainable financing, and financial protection. (who.int)
Health emergencies and international rules
WHO’s Health Emergencies Programme supports preparedness, early warning, risk assessment, response, and recovery. During crises, it coordinates with governments and partner organizations, provides technical expertise, and helps maintain essential health services. Its emergency work includes disease surveillance, laboratory capacity, risk communication, and coordination of medical teams and supplies. It has operational responsibilities as well as an advisory role. (who.int)
The International Health Regulations (IHR) provide a framework under international law for cooperation against the international spread of health threats. The regulations establish obligations concerning surveillance capacities, notification, and response, while seeking to avoid unnecessary interference with international traffic and trade. Amendments adopted in 2024 entered into force on 19 September 2025 for states to which they apply, with rejection and reservation procedures affecting applicability. WHO recommendations do not give the organization authority to impose domestic lockdowns or other health restrictions on national populations. (apps.who.int)
Historical programmes and treaty-making
WHO launched an intensified smallpox eradication programme in 1967. International cooperation combined vaccination with surveillance and containment of outbreaks. The last known naturally occurring case was recorded in Somalia in 1977, and WHO declared smallpox eradicated in 1980. The programme depended on collaboration among national authorities, health workers, and international partners. (who.int)
The WHO Framework Convention on Tobacco Control was the first international treaty negotiated under WHO’s auspices. Adopted on 21 May 2003, it entered into force on 27 February 2005. It establishes a legal framework for participating states’ tobacco-control measures, including provisions addressing taxation, advertising, packaging, and exposure to tobacco smoke. (fctc.who.int)
Financing
WHO receives assessed contributions—membership dues calculated in relation to countries’ wealth and population—and voluntary contributions from governments and other partners. Voluntary funding may be flexible, thematic, or earmarked for specified programmes and periods. The distinction affects how readily resources can be allocated across the approved programme budget. In 2022, member states approved a financing reform intended to increase assessed contributions to cover 50% of WHO’s base budget by 2030; this target concerns the base budget, not all organizational expenditure. (who.int)