Zygomycosis

Zygomycosis describes the infections caused by several related species of fungus that occur naturally in soil and decaying vegetable matter.  The immune system of most persons can easily resist the fungus, but in individuals who are immunocompromised, it occasionally can grow within the human body.  When it does affect a person, it grows faster than most other infections.  It usually starts in the nose and sinuses and from there spreads to the digestive tract and skin.
Treatment is with anti-fungal drugs to stop the spread of the fungus, plus surgery to remove dead and infected tissue.  As such, the chance of mortality in each patient is highly variable. 
As pointed out in the episode Who's Your Daddy?, the fungus that causes zygomycosis thrives in very wet conditions, in this case, a studio with sound-absorbent insulation.
Zygomycosis at Wikipedia
Zygomycosis