As May progresses, school children around the world (okay, in the Northern Hemisphere at least) are preparing for their end of year exams. And sometimes, the stress can be overwhelming. A few kids here and there falling ill wouldn’t be unexpected, and of course, there are a few more who fake a sickness to buy themselves another day or two of studying.

But in Portugal back in 2006, things got a bit out of hand. At about the same time, a handful of high schoolers across many different schools each complained of the same symptoms: dizziness, difficulty breathing, and rash, but with no discernable cause. And this mystery illness appeared contagious. Within a few days, it had spread significantly; before the week was out, nearly 300 students across 14 different high schools showed the same set of ailments. The epidemic was so bad that some schools, perhaps out of an abundance of caution, closed down for a few days.

Medical tests showed nothing out of the ordinary — or, at least, nothing common among the afflicted which would account for the similar ailments. But when they looked to another source, health officials found something to go on. The cause, they concluded, was morangos com açúcar, or strawberries with sugar. And an extraordinary number of Portuguese teens were exposed to it.

But Morangos com Açúcar wasn’t an artificially sweetened fruit snack. It was a television program.

Morangos com Açúcar was a teen soap opera which aired on the Portuguese TV station TVI from 2003 to 2012. It followed the lives of fictional high schoolers as they went to school and did teenager stuff, just with often preposterous plot lines. At its peak popularity — the summer of 2005 — it claimed a viewing share of 42%; that is, about four out of every ten people in watching TV in Portugal at the time were watching the show. Assuming that almost all of them were teens — who else watches teen soaps? — it’s fair to say that the show was extraordinarily popular among high school kids in Portugal.

And in 2006, the kids on Morangos com Açúcar got sick. Very sick — a life-threatening virus had gripped the fictional school population. The sick kids in the show had — you guessed it — dizziness, difficulty breathing, and rash. Such a plotline isn’t all that odd, but in this case, it didn’t end when the viewers turned off the television. The real school kids starting showing similar symptoms just a few days after the episode aired — per Hindustan Times, “medical officials believe many children, after watching the show, feared their own minor rashes and wheezes were something serious.” For the first time ever, a fake television disease had caused a real-life one.

But it didn’t end there. The first round of afflicted teens begat a second as their friends, now seeing common ailments manifest as something major, also convinced themselves that they, too were sick, and so on and so forth. Within a week, hundreds of Portuguese high schoolers were convinced that the end of times was at hand.

It wasn’t. The students weren’t sick, at least not in the traditional sense. Instead, per Wikipedia, “the Portuguese National Institute for Medical Emergency eventually dismissed the illness as mass hysteria,” and at no point were the lives of any students actually in danger. Well, at least not in medical danger. The students still had to take their final exams, and did so once the Strawberries with Sugar virus passed.

Bonus fact : Soap operas look different than most TV shows by design — or more accurate, by budget. As Mental Floss explains, daytime TV ad slots aren’t worth as much as revenue as primetime ones, and airing new episodes daily (instead of weekly) creates a double whammy — you make less money and have to produce more to do so. To compensate, they cut costs: soaps use fewer lights, fewer cameras, and often use lower quality camera equipment. All of that is noticeable in the end product.