Mass hysteria is when delusions or other symptoms of mental illness seem to spread through a whole population of people. Listverse has ten strange cases of the phenomena from the not-so-distant past. One affected those who followed the Portuguese soap opera Morangos com Açúcar.
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In May, 2006, an outbreak of the “Morangos com Açúcar Virus” was reported in Portuguese schools. 300 or more students at 14 schools reported similar symptoms to those experienced by the characters in a recent episode. These included rashes, difficulty breathing, and dizziness, forcing some schools to close. The Portuguese National Institute for Medical Emergency dismissed the illness as mass hysteria. This story concerned some parents because of the major influence this series has on the kids and teens that watch, it was in newspaper and magazines articles and elsewhere.
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To dismiss most of these items by calling them mass hysteria, is quite a disservice to the reader, because it stops short of getting to the real mystery.
http://discovermagazine.com/1995/apr/analysisofatoxic493
The possible truth is way more weird.