The Tanganyika laughter epidemic is sometimes understood as implying that thousands of
people were continuously laughing for months. However this may not have been the case. Other reports tell that the epidemic consisted of occasional attacks of laughter among groups of people, occurring throughout the vicinity of the village of Kashasha at irregular intervals. According to reports, the laughter was incapacitating when it struck.
The school from which the epidemic sprang was sued; the children and parents transmitted it to the surrounding area. Other schools, Kashasha itself, and another village, comprising thousands of people, were all affected to some degree. Six to eighteen months after it started, the phenomenon died off. The following symptoms were reported on an equally massive scale as the reports of the laughter itself: pain, fainting, respiratory problems, rashes, attacks of crying, random screaming. Doctors reported that there were more complaints about gas than ever before.
From: http://en.wikipedia.org/wiki/Tanganyika_Laughter_Epidemic
