Kuru is a transmissible prion disease that causes progressive brain damage. The name of the disease is from the word "shake" in the Fore language - the only known ethnic group that suffers from the condition. It's also known as "laughing sickness" as people suffering from the condition will often break out in spontanous pathological laughing. It's believed that the disease can only be transmitted by eating the brain of a person affected with the condition. The Fore practiced cannibalism well into the 20th century.
The disease was first observed in Western medicine in the 1950s, where people suffering from it exhibited general weakness that eventually progressed to inability to walk or take in nourishment, leading to death. The disease was widespread among the Fore. In the 1960s, American researchers managed to give chimpanzees the disease by injecting them with biological samples taken from the disease's victims.
Kuru was the first known of the transmissible spongiform encephalopathies and allowed for other breakthroughs that traced similar diseases in the west to the eating of meat tainted with the tranmissible element.