Mass hysteria? Common in girls schools

In late January of 1962, at an all-girls school in Kashasha, Tanzania, three girls began to laugh uncontrollably. They didn’t stop, even when disciplined by their teachers. Bizarrely, the laughter spread until more than 90 students were laughing for no apparent reason. The laughing fits allegedly lasted anywhere from a few hours to more than 15 days. Officials tried to find a cause but were unsuccessful. The epidemic laughter led to the closure of schools as the laughing spread to other villages nearby. Its cause remains unknown. The laughter episodes continued on and off for about one year, and then mysteriously ceased.