The Psychopath Plague — Steven Spruill

It came from nowhere to strike the Earth a maddening blow! The only symptom is sudden psychosis, and no one is immune. Once again intrepid investigator Elias Kane and his giant, alien sidekick Pendrake are called upon to do the impossible: find the cure for a disease that has no traceable source. The computers are definitive: In forty-nine days most of the world's population will be murderously insane. The Earth's police commissioner wants Kane off the case. Kane wants off the planet and alluring beauty Elizabeth Tyson knows more tha she admits about The Psychopath Plague...