Seven mysterious mass illnesses that defied explanation – from ‘meowing nuns’ to laughter epidemic

A terrifying incident at Heathrow Airport’s Terminal 4 – believed to have been caused by CS gas –was originally blamed on “mass hysteria”. But what does that really mean? Dancing in the streets - but not in a fun way (Image: Alamy Stock Photo)

Heathrow Airport’s Terminal 4 was evacuated earlier this week as 20 people reported injuries amid fears of a “hazardous materials incident”. ‌

The Met initially put the episode down to “mass hysteria” before a man was arrested on suspicion of possessing CS gas. ‌

But spates of unexplained collective behaviour have broken out before. Now we take a look at the freaky phenomenon… ‌

Boogie man: In July 1518, a woman called Frau Troffea started throwing some shapes on the streets of the city of Strasbourg in modern day France - an