Arthur Pyuty wa Yoru no Majo

The human race has been infected by a strain of bacteria that was originally isolated in South America but has spread all over the world. The symptoms start with fever and vomit and eventually ends with the person in a coma. However, those who awake from that coma are those with incredible intelligence and they're soon able to see that they are in fact being ruled by higher beings that they thought only existed in fairy tales like demons and witches.