In 1984 he was presented with a number of patients with a prolonged exertional 'flu-like illness, but presenting no diagnosable condition. While some people thought they were no different from commonly found "tired all the time" cases, Dr Snow was convinced that they were indeed sick and proceeded to investigate.
In 1984, Dr. Snow encountered a group of patients with prolonged exertion-related symptoms resembling flu but without a clear diagnosis. Some people dismissed them as typical cases of fatigue, but Dr. Snow believed they were truly sick and began investigating their condition.