Hillary and others having kuru implies child farms. Kuru is spread by, not caused by, cannibalism. The cannibals must have eaten other cannibals. In this case the leftovers from the victims would have been fed to future victims. Because of kuru's long incubation period, the disease would have been able to spread undetected until adult cult members started to fall ill. It probably hasn't been that many years since that time, which means that there should be many more cases that are still asymptomatic.