The flag of the World Health Organization is the United Nations flag with a snake climbing through it. Take the UN's white polar map and olive branches, center them on the same light blue field, then lay a golden staff down the middle with a single serpent coiled around it, and you have the banner of the world's health agency. The staff belongs to Asclepius, the Greek god of healing, and it makes the WHO flag the carrier of the oldest medical symbol still in daily use, a design whose core element predates the organization by roughly two and a half thousand years.
Chosen at the first assembly
WHO was born in two stages. Its constitution was signed by 61 states on July 22, 1946, but only entered into force on April 7, 1948, once enough ratifications had arrived. That April date is now World Health Day, the one day a year the flag reliably appears in news photographs worldwide. In June and July of 1948 the First World Health Assembly convened in Geneva to set the new agency running, and among its decisions was the choice of an emblem: the United Nations symbol surmounted by a staff with a snake coiling round it.
The UN base was standard practice for the new specialized agencies, an instant visual statement of membership in the family. (How that polar map and wreath came to exist at all, sketched in a rush for the 1945 San Francisco conference, is told in our United Nations flag entry.) The addition was the interesting part. Where UNICEF would later insert a mother and child and UNESCO would build a temple out of its own initials, the health agency reached back to antiquity and picked up the sign of a Greek god. Resolution WHA1.133 of that first assembly still governs use of the emblem and the organization's name, and member states are asked to prevent unauthorized use, particularly in commerce.
Why a snake and a staff
Asclepius was the Greek god of healing, a physician deified, whose cult spread through the Mediterranean from around the fifth century BC. The sick traveled to his sanctuaries, the Asclepieia, the most famous at Epidaurus, where treatment mixed baths, diet, rest and a night in the temple during which the god was expected to visit dreams. Snakes were part of the apparatus. Non-venomous serpents lived in the sanctuaries and appear constantly in the iconography; the species associated with the cult, a glossy brown European rat snake, carries the name Aesculapian snake to this day. Statues showed the god leaning on a rough staff with a single serpent wound around it.
Why a snake should mean healing has kept classicists busy. The animal sheds its skin whole and emerges apparently new, a ready image of recovery. Snakes were also chthonic creatures, in touch with the underworld that sick people hoped to avoid, and their venom was both poison and drug, which is not a bad summary of pharmacology. Whatever the original logic, the association held for two millennia. When the delegates in Geneva wanted a sign that would read as "medicine" in every member state, the staff of Asclepius was the obvious and, usefully, the culturally least loaded choice.
The wrong snake
The WHO emblem is regularly misidentified as a caduceus, and the distinction is worth keeping. The caduceus is the wand of Hermes: two snakes intertwined up a winged staff. Hermes was the messenger god and patron of merchants, travelers and, less flatteringly, thieves, so his wand historically signaled commerce and negotiation rather than healing. The mix-up is mostly an American export. Through a 19th-century chain of accidents involving publishers and military insignia, the US Army Medical Department adopted the caduceus in 1902, and the error propagated through American hospitals, insurers and clip art. The medical historian Walter Friedlander, who surveyed American health-related organizations in the 1990s, found that professional medical associations mostly used the one-snake rod while commercial healthcare companies leaned heavily toward the two-snake caduceus, a division he noted with some satisfaction. WHO has never wavered: one snake, no wings.
From emblem to flag
For its first thirteen years the organization had an emblem but no flag of its own. That changed in 1961, when the Fourteenth World Health Assembly adopted resolution WHA14.24, deciding that the WHO flag would be the official emblem of 1948 centered on a United Nations blue background. A formal flag code, issued in 1982 on the model of the UN's, fixes the details: the field is UN blue, the map and branches white, and the staff and serpent gold, the one touch of a third color in an otherwise standard UN family flag. The code follows UN practice on geometry, with the emblem standing half the height of the hoist, and accepts the usual range of proportions, 2:3 and 3:5 among them.
The rules of use are strict in the familiar UN way: the flag may not be subordinated to national flags, may not be used commercially, and is lent out rather than freely distributed. WHO collaborating centres, for instance, may obtain a flag for specific occasions such as World Health Day rather than for permanent display. In ordinary times the flag lives an administrative life, flying at the Geneva headquarters, at the six regional offices from Brazzaville to Manila, and at country offices in the field. In extraordinary times it travels: on vehicles and tents during outbreak responses, at vaccination campaigns, and behind the podium during the press briefings that made the emblem globally familiar during the COVID-19 pandemic, when the blue backdrop with the gold staff appeared on screens daily for the better part of two years. Few flags get that kind of exposure, and fewer still owe it entirely to bad news.
References
[1] World Health Organization, "The WHO logo and emblem." https://www.who.int/about/policies/publishing/logo
[2] World Health Organization Flag Code and Regulations (1982). https://cdn.who.int/media/docs/default-source/whocc/flagregulations.pdf
[3] First World Health Assembly, resolution WHA1.133 (1948), on the use of the WHO name and emblem; Fourteenth World Health Assembly, resolution WHA14.24 (1961), adopting the flag.
[4] Walter J. Friedlander, The Golden Wand of Medicine: A History of the Caduceus Symbol in Medicine (Greenwood Press, 1992).
[5] Flags of the World (FOTW), "World Health Organization." https://www.fotw.info/flags/un-who.html
[6] Constitution of the World Health Organization, signed 22 July 1946, entered into force 7 April 1948. https://www.who.int/about/governance/constitution