Possible Call of Cthulhu scenarios:
1) Dude murdered while updating his blog. His ghost messes with people who visit his site. Players have to solve the murder to stop the ghost from attacking more people.
2) "For The Love of Y'golonac." There's no point speculating whether the hungerlust started in raccoons, rats or monkeys before infecting humans. It's not a mutation of AIDS like some fools believe, and it wasn't sent by Jehovah to punish sinners. More likely it was sent by Y'golonac as a reward for those who sin creatively. At least, that's what some of his followers believe. Picture a rabid dog humping your leg while it tears filets mignons out of your thigh. Now picture Alan Greenspan trying to do the same thing. Players have opportunity to catch the disease before it gets loose. Within a few days of contracting the disease, its victims are too hungry to care what they eat, and usually begin self-cannibalism. Genetically engineered from captured trans-dimensional beings? Government or cult spreading the disease?