health

Fungal infections are caused by fungi, tiny microbes found in soil,
air, and water, as well as on plants, animals, and people. Fungi feed on
other organisms, living or dead, and play an important role in helping
dead plants and animals decay. There are at least 100,000 species of
fungi. The most familiar types of fungi are the mushrooms, the fuzzy
white or blue-green mold that grows on forgotten foods in the back of
the refrigerator, and the mildew on the shower curtain. Fungi grow best
in warm, moist areas such as a steamy bathroom or the spaces between
the toes.
Relatively few species of fungi cause fungal infections, also called
mycoses (my-KO-seez), in humans. Fungal infections are of two basic
types: superficial infections and systemic infections. Superficial infections
affect the surface of the body, the skin, the nails, and the hair. They most
often occur in moist areas, such as between the toes, in the crotch, or in
the mouth.
Systemic infections take hold inside the body, in individual organs or
throughout the body, and can cause severe or even fatal illness. System
infections are most likely to develop in people who have weak or suppressed
immune systems, such as the following:

• People with leukemia (cancer of the blood cells), Hodgkin’s disease,
  or other kinds of lymphomas (cancers of the immune system)
  
• People receiving chemotherapy or radiation treatment
  
• People with AIDS
  
• People who have uncontrolled diabetes
  
• People who have received an organ transplant
  
• People who are taking any type of drug that suppresses the immune
  system. For example, in September 2008, the U. S. Food and Drug
  Administration began an investigation into the risk of increased
  fatal fungal infections in people taking immunosuppressant drugs
  for rheumatoid arthritis.

In these people, the infections can cause chronic* disease and, in some
cases, death.