Introduction
Fungi are a type of plant that can infect people. Yeasts, molds, and mushrooms are all examples of fungi.
Some fungi reproduce by spreading microscopic spores. These spores are often present in the air, where they can be inhaled or come into contact with the surfaces of a person's body. Consequently, fungal infections usually begin in the lungs or on the skin. Of the wide variety of spores that land on the skin or are inhaled into the lungs, most do not cause infection. Except for some superficial skin conditions, fungal infections are rarely passed from one person to another.
Certain types of fungi (such as Candida) are normally present on body surfaces or in the intestines. Although normally harmless, these fungi sometimes cause local infections of the skin and nails (see Section 18, Chapter 212), vagina (see Section 22, Chapter 247), mouth (see Section 8, Chapter 110 and Section 8, Chapter 115), or sinuses (see Section 19, Chapter 221). They seldom cause serious harm, except in people with a weakened immune system or with foreign material (such as an intravenous catheter) in their body.
Sometimes, the normal balances that keep fungi in check are upset and infections occur. For example, the bacteria normally present in the digestive tract and vagina limit the growth of certain fungi in those areas. When a person takes antibiotics, those helpful bacteria can be killed--allowing the fungi to grow unchecked. The resulting overgrowth of fungi can cause symptoms, which are usually mild. As the bacteria grow back, the balance is restored, and the problem usually resolves.
Some fungal infections (for example, histoplasmosis, blastomycosis, and coccidioidomycosis) can be serious in otherwise healthy people.
Some fungal infections are more common in certain geographic areas. For example, in the United States coccidioidomycosis occurs almost exclusively in the Southwest, whereas histoplasmosis is especially common in the Ohio and Mississippi River valleys. Blastomycosis is particularly common in the eastern and central United States and in Africa.
Because many fungal infections develop slowly, months or years may pass before a person seeks medical attention. In people with a weakened immune system (for example, people who have received an organ transplant, are being treated for cancer with immunosuppressive drugs, or who have AIDS), fungal infections can be very aggressive--spreading quickly to other organs and often leading to death.
Several drugs effective against fungal infections are available, but the structure and chemical makeup of fungi make them difficult to kill. Antifungal drugs may be applied directly to a fungal infection of the skin or other surface, such as the vagina or the inside of the mouth. Antifungal drugs may also be taken by mouth or injected when needed to treat more serious infections. Several months of treatment are often needed.
 See the sidebar Risk Factors for Developing Fungal Infections.
 See the drug table Drugs For Serious Fungal Infections.
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