The Viral effect of laughter!

Laughter is contageous, isn't it. You know how difficult it is to resist when someone else is laughing heartily - think of actors 'corpsing' when reading through their lines. Once it starts spreading, laughter can be quite difficult to contain in its viral effect.

In fact in 1962 there was a laughter epidemic in Africa which started off in a girls' boarding school in Tanzania. The first symptoms appeared on January 30, when three girls got the giggles and couldn't stop laughing. The symptoms quickly spread to 95 students, forcing the school to close on March 18. The girls sent home from the school were focal points for the further spread of the epidemic. Related outbreaks occurred in other schools in Central Africa and spread like wildfire, ceasing two-and-a-half years later and afflicting nearly 1,000 people.