By James Moore

Copyright dailystar

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 – and didn’t stop. Before long up other people had started dancing frantically. Some 400 were affected, often doing it for weeks on end, with some dying of fatigue. Then, suddenly, it all stopped. Theories include mass stress following a famine. Feline funny : Back in the Middle Ages, a series of mass hysteria incidents occurred among groups of nuns. In one case in Germany a nun started biting her fellow nuns and then the others started joining in. Over in France a nun began meowing and before long all the nuns in the convent were, puzzlingly, imitating cats. Just car-azy: Residents of the town of Bellingham in the US state of Washington began collectively noticing something strange in 1954 – pitting marks in the windscreens of their cars. Before long people across the region were reporting them, worrying that fallout from H-bomb testing was to blame or acid from flying bugs. But when police conducted tests on the vehicles they found the pitting was mostly down to normal wear and tear. No joke : On January 30, 1962, three girls started guffawing uncontrollably at a school in the village of Kashasha in Tanzania. The laughing epidemic spread through the building, to their parents and then other villages too. Over the next few months 1,000 people were affected, each maniacally chuckling for a week, on average. No cause was ever found. Fainting frenzy : In October 1965, pupils at a girls’ school in Blackburn, Lancashire, started inexplicably fainting over the course of several days, with 150 affected. An ambulance driver recalled: “As fast as we took them away, new cases from classrooms in other parts of the school were being brought in.” Some blamed fears over a recent polio epidemic, others food poisoning or a gas leak, but a report eventually put the cases down to ‘over-breathing’. Field of nightmares : Fifteen years later a similar fainting fit gripped 300 children who were attending a marching band competition at Hollinwell Showground in Nottinghamshire. A witness described them “falling like nine pins” at the event on July 13, 1980, with 250 taken to hospital. Chemicals in crop spray were suspected, but an official report concluded ‘mass hysteria’ was to blame. Clowning around : A stunt involving someone dressed as a clown for a horror film in Green Bay, Wisconsin, in the US in 2016 sparked a worldwide mass panic involving the sightings of evil clowns – mostly false. They were reported from the UK to New Zealand and often involved the creepy entertainers lurking in woods or near schools.