‘There was an explosion, and I had to close my eyes’: how TV left 12,000 children needing a doctor

The Japanese government held an emergency meeting and share prices crashed after a Pokemon broadcast. For years, its effects went unexplained - until researchers started digging ...

Twenty-five years ago, at precisely 6.51pm on 16 December 1997, hundreds of children across Japan experienced seizures. In total, 685 - 310 boys and 375 girls - were taken by ambulance to hospital. Within two days, 12,000 children had reported symptoms of illness. The common factor in this sudden mass outbreak was an unlikely culprit: an episode of the Pokemon cartoon series.

The instalment in question, Denn Senshi Porygon (Electric Soldier Porygon), was the 38th in the Pokemon anime's first season - and initially, at least, it sparked a medical mystery. Twenty minutes into the cartoon, an explosion took place, illustrated by an animation technique known as paka paka, which broadcast alternating red and blue flashing lights at a rate of 12Hz for six seconds. Instantly, hundreds of children experienced photosensitive epileptic seizures - accounting for some, but far from all, of the hospitalisations.