On the morning of Tuesday, 30 January 1962, at the Kashasha Mission Girls’ School on the western shore of Lake Victoria — in what had been British Tanganyika until a few months earlier and would shortly be the new nation of Tanzania — three students aged twelve to eighteen began to laugh, in class, and could not stop.
Within a few hours the laughter had spread to 95 of the school’s 159 students. Some of them also cried; some became restless and tearful; a few struck out at people trying to help. The episodes lasted anywhere from a few minutes to several hours. They came and went. By the afternoon the school’s headmistress, unable to restore order, sent the affected students home.
This did not contain the outbreak. It distributed it. The girls returned to their home villages — most of them in the Bukoba district, the lakeshore region just south of the Uganda border — and within ten days similar laughter episodes were being reported in the village of Nshamba, where a number of the Kashasha students lived. The Nshamba episodes affected at least 217 villagers. Over the following six months the laughter moved from village to village along established kinship lines, traveling roughly with the speed of footpath travel between settlements. It reached Bukoba town in early April. It closed at least fourteen schools and is documented to have affected roughly a thousand people. It lasted, in declining intensity, for about eighteen months. The last recorded episode was in June 1964.
What the doctors found
A Bukoba district medical team led by Dr. A. M. Rankin investigated within the first month. They examined affected and unaffected individuals from the same households. They took blood samples. They tested for infectious agents. They tested for toxins. They found nothing.
Rankin and his colleague P. J. Philip published their report in 1963 in the Central African Journal of Medicine. The paper described the affected individuals as “physically normal but emotionally disturbed,” concluded that no pathogen or chemical agent was responsible, and classified the episode — using the term then standard in psychiatric practice — as mass hysterical reaction (the modern term is mass psychogenic illness). They could find no demographic predictor for who would be affected and who would not, beyond a strong tendency for affected individuals to be members of communities where someone they knew had already been affected.
The mechanism, in current understanding, is the same one that produced the dancing plague of 1518 in Strasbourg: in a population under significant social stress, a culturally available trance behavior can spread through a community as people, witnessing the affected, enter the same dissociative state. The expression varies by culture. Sixteenth-century Strasbourg had Saint Vitus, so the behavior was dancing. Mid-twentieth-century Tanganyika had no comparable cultural script; the behavior took the more diffuse form of uncontrollable laughter and weeping.
The stresses in the Bukoba district in early 1962 were real. Tanganyika had become independent of Britain only six weeks before, on 9 December 1961. The Mission schools were operated by European Christian denominations whose role in the new African state was suddenly uncertain. The Kashasha school in particular was operated by an order whose European teachers had been informed that their contracts might not be renewed. The students at these schools were under intensified academic pressure, often the first generation in their families to receive any formal education, and acutely aware that the political ground beneath the institutions they attended was shifting. Hempelmann’s 2007 review of the medical literature concluded that this constellation of stresses was the most plausible trigger.
What it became
The Tanganyika episode has become, in the half-century since, one of the standard case studies in mass psychogenic illness — cited in every undergraduate psychology textbook that covers the topic, usually in a sentence or two, often inaccurately. The most common inaccuracy is the duration. A widely repeated version of the story claims the laughter lasted six months or one year; the actual duration, according to the original Rankin report, was eighteen months. The second most common inaccuracy is the death count. A persistent urban-legend version claims that several people “laughed to death.” There is no documented death attributable to the epidemic. The original report records only that some affected individuals developed exhaustion, dehydration, and minor injuries from falls during episodes. All survived.
The Kashasha Mission School is still operating, though under different management. It is now called the Kashasha Roman Catholic Girls’ Secondary School and serves several hundred students. The current headmistress, asked in a 2012 interview by a Tanzanian newspaper whether the school still discussed the 1962 events with students, said: They know about it. We do not tell them not to laugh.