Pertussis gets my vote. Had it as a kid, great fun. I think it often gets mistaken for demonic possession. Similar problem with dengue fever. No coughing, just debilitating pain in the bones.
Dengue is no longer quite so likely to have a fatal outcome, with proper treatment.
It is truly frightening. There are those who contend that overpopulation is an illusion. Gaia takes care of herself. Like the child who is better off controlling his behavior than facing the consequence, we should try to control the population ourselves by the means we have instead. It will be far more pleasant.