There was nothing wrong with the drink, it turns out; the problem lay with the drinkers. The trace of hydrogen sulphide found in some bottles and the smear of fungicide on the outside of some cans was not enough to cause illness. The victims instead succumbed to mass hysteria.
That is the conclusion offered by scientists from the University of Leuven in a letter in the current edition of The Lancet.
They chart how the illness started (striking down 26 children in one school, 18 of whom were detained in hospital), how it was spread (by blanket media coverage), how suggestibility of the local population was high (because of the recent scare about dioxins in food) and how the flames of the epidemic were fanned by the over-reaction of the health authorities and the Coca- Cola company, which had been thoroughly alarmed by the dioxins incident. The result: "mass sociogenic illness", which required "social healing" not "medical care".
Mass sociogenic illness has a long pedigree. Outbreaks have been common since the Thirties but the phenomenon can be traced back centuries. I am indebted to Professor Simon Wessely, consultant psychiatrist at King's College Hospital and The Maudsley Hospital in London, for the following list of examples.
One of the most dramatic outbreaks occurred at the Nottingham Schools Jazz Band Festival in 1980. It was a hot day, a couple of children fainted and then a rumour went round that a local farmer had sprayed a nearby field with pesticide. Hundreds collapsed and the event received wide press and TV coverage, but no cause was ever found. Almost two decades later some of those involved still believe that they were victims of a toxic spray.
The Nottingham incident had followed a similar one at the Hazelrigg jazz festival eight years earlier. A girl playing the big drum fainted, and 129 others in the audience followed. The cause was blamed on a weedkiller, which would have had to be highly selective as only girls were affected, or on a gas leak from the North Sea.
Although women, and especially schoolgirls, are common victims of the outbreaks, men are affected too. At an army base in Santiago, 1,000 soldiers succumbed to a mystery gas in 1988. In a separate incident in California in 1994, hospital staff attending a dying patient fell ill, claiming that his body had emitted poisonous fumes. Some remained sick more than five years later.
According to Professor Wessely, the outbreaks have some common features. They are usually spread via line of sight - only those with a direct view of people collapsing are affected. If an incident affects a teacher or nurse - someone in authority - a mass reaction may follow. Often these occur in tense situations.
The key to containing incidents is to identify them early as outbreaks of hysteria. It is when the emergency services respond, with helicopters, ambulances and police, that the situation is made worse. A soothing hand on the brow, or equivalent, can heal while a stretcher to hospital can harm. Coca-Cola and the Belgian authorities should take note.