The phrase "mysterious sickness" refers to an illness or disease that is difficult to understand or diagnose because its cause or symptoms are unclear or unknown. Full definition
She also counseled patients who had come to the Undiagnosed Diseases Network after years of trying to put a name on a mysterious sickness, explaining whether new technologies like exome sequencing might help and discussing patients» hopes and expectations. (sciencemag.org)
This stunning South Korean horror film sees a policeman and a shaman team up to solve a mysterious sickness spreading through a village. (vodzilla.co)
As the paranoia spreads and they turn on one another, they discover a mysterious sickness could be the culprit. (uproxx.com)