Fungal (FUNG-gul) infections are caused by fungi (FUNG-eye) that can grow on the skin, nails, and hair and within the body.
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. Estimates of the number of fungal species in the world vary wildly. Some assessments put the number at 1.5 million, but a 2015 study by the University of Tartu National History Museum found only around 45,000. The most familiar types of fungi are 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.
Only around 300 species of fungi cause fungal infections, also called mycoses (my-KO-seez), in humans. Fungal infections are of two basic types: superficial (or localized) infections and systemic infections. Superficial infections affect only one area of the body, most commonly the skin and nails or moist areas such as the crotch and mouth. They are annoying but typically not very serious.
Systemic infections take hold inside the body, in individual organs or throughout the body, and can cause severe or even fatal illness. Systemic infections are most likely to develop in people who have weak or suppressed immune systems * , such as the following:
In these people, the infections can cause chronic * disease and, in some cases, death.
Tinea (TIH-nee-uh) is a general term given to a group of localized fungal infections that affect the nails, feet (athlete's foot), groin area (jock itch), scalp, or skin (ringworm). Trichophyton and Microsporum fungi cause these related infections. Ringworm is identified by a red, scaly patch on the skin that looks like an expanding ring around a clearing center. Three different types of fungi that live in soil cause ringworm. Humans contract the infection through contact with this soil or with an infected animal or other person. Symptoms of athlete's foot include redness and cracking of the skin between the toes, and infected nails on the hands or feet usually look white and appear to be crumbling. Wearing damp socks or shoes makes it easier for the infection to take hold. Athlete's foot is spread through contact with an infected person, surface, or item, such as a floor or towel.
Aspergillosis (as-per-jih-LO-sis) is the name for a variety of systemic infections caused by Aspergillus (as-per-JIH-lus) fungi. If it is inhaled through the mouth or nose, the fungus can cause a mild allergic reaction or a more serious infection of the sinuses * and lungs. Symptoms of aspergillosis vary and may include fever, cough, chest pain, and wheezing. In severe cases, typically seen in people with weak immune systems, the infection can spread to other organs, including the brain, skin, and bones.
Blastomycosis (blas-toh-my-KO-sis) is a systemic infection caused by the Blastomyces dermatitidis fungus commonly found in soil in the southeast, midwest, and south central United States. The disease's symptoms resemble those of the flu: joint and muscle pain, a cough that brings up sputum * , fever, chills, and chest pain. If it progresses, it can lead to chronic pulmonary * infection, causing permanent lung damage, or widespread disease that affects the bones, skin, and genital and urinary tracts. Blastomycosis leads to death in about 5 percent of patients.
Coccidioidomycosis (kok-sih-dee-oyd-o-my-KO-sis) is a systemic infection caused by Coccidioides immitis, a fungus found in soil in the southwestern United States, Mexico, and South America. Most people with coccidioidomycosis have no symptoms, but 40 percent of patients experience a flulike illness, with fever, rash, muscle aches, and cough. Also known as valley fever, the infection can cause pneumonia * or widespread disease affecting the skin, bones, and meninges, which are the membranes covering the brain and spinal cord.
Cryptococcosis (krip-toh-kah-KO-sis) is a systemic infection caused by the fungus Cryptococcus neoformans, usually found in soil or bird droppings. Typically, the fungus enters the body through the mouth or nostrils when someone inhales fungi spores * , and symptoms of a lung infection, such as cough and chest pain, may develop. Although infection with Cryptococcus usually produces no symptoms or only mild symptoms in healthy people, the infection may spread in people who have weak immune systems. If it spreads to the central nervous system, it can cause inflammation of the meninges. This complication is especially common among people with AIDS.
Histoplasmosis (his-toh-plaz-MO-sis) is usually a mild systemic infection caused by Histoplasma capsulatum. This fungus is found in the eastern and central United States in soil that contains bird and bat feces * . When the soil is disturbed, the fungal spores may be inhaled. Histoplasmosis can cause flulike symptoms, including body aches, fever, and cough. Most people who become infected do not experience symptoms, but as with other fungal infections, people with weak immune systems are at risk for severe disease. In those cases, the infection affects the lungs and may spread to the liver * , spleen * , bones, and brain.
Mucormycosis (mu-cor-my-KO-sis) is caused by a fungus found on decaying plants. Most people do not get sick from exposure to this fungus. However, people with weakened immune systems or uncontrolled diabetes are susceptible to becoming sick. Mucormycosis often starts with a sinus infection. Infection then spreads to the brain and sometimes to the lungs, skin, digestive system, and kidneys. The death rate for this fungal infection ranges from 30 to 70 percent, depending on where the infection is located.
Sporotrichosis (spo-ro-trih-KO-sis) is a skin infection caused by the Sporothrix schenckii fungus, which is found in soil, thorny plants, hay, sphagnum (SFAG-num) moss, and other plant materials. It enters the skin through a small cut or puncture, such as a thorn might make. Soon, small reddish bumps resembling boils * form around the cut and often ulcerate * . In some cases, infection can spread to other parts of the body, such as the lungs or joints.
Superficial fungal infections, such as athlete's foot and candidiasis, are very common. Systemic infections, by contrast, are rare, appearing in fewer than 1 to 2 people in every 100,000 in the United States, according to the Centers for Disease Control and Prevention (CDC). They are more common in certain populations, such as people with AIDS or those who have had organ transplants.
With the so-called endemic * mycoses, rates of disease are higher in specific geographic areas. For example, coccidioidomycosis (also known as Valley fever) occurs in about 42 of every 100,000 people in parts of the southwestern United States and leads to around 150,000 infections annually. In areas where histoplasmosis is found, 60 to 90 percent of the population tests positive for exposure to H. capsulatum, but the disease develops only in people with weak immune systems.
Most superficial fungal infections are diagnosed based on their appearance and location. A doctor may also take a skin scraping to examine under the microscope or to culture * in a laboratory. Some fungi glow with a particular color under ultraviolet * light, so a doctor may make the diagnosis by shining such a light on the affected area. Systemic infections can be diagnosed by collecting a sample of blood, urine, cerebrospinal fluid * , or sputum to culture.
Most superficial fungal infections are treated at home with antifungal creams or shampoos for one to two weeks. Oral (taken by mouth) antifungal medication also may be prescribed, if necessary. Some cases of fungal infection are more persistent and may need to be treated with medicine for two to four weeks or even longer. Systemic illnesses often require hospitalization so that the patient can receive intravenous * antifungal drugs and supportive care.
Preventing fungal infections can be difficult, because fungi are everywhere. In general, people who are otherwise healthy rarely contract systemic fungal infections. Practicing good hygiene, keeping the skin dry, changing socks and underwear daily, and avoiding walking barefoot can help prevent superficial skin infections.
See also Skin and Soft Tissue Infections • Valley Fever • Yeast Infection, Vaginal
Hospenthal, Duane R., and Michael G. Rinaldi. Diagnosis and Treatment of Fungal Infections, 2nd ed. New York: Springer, 2015.
Richardson, Malcolm D., and David W. Warnock. Fungal Infection: Diagnosis and Management, 4th ed. Hoboken, NJ: Wiley-Blackwell, 2012.
MedlinePlus. “Fungal Infections.” U.S. National Library of Medicine, National Institutes of Health. https://www.nlm.nih.gov/medlineplus/fungalinfections.html (accessed March 31, 2016).
Merck Manuals: Consumer Version. “Fungal Infections.” http://www.merckmanuals.com/home/infections/fungal-infections/ (accessed March 31, 2016).
American Academy of Dermatology. 930 E. Woodfield Road, Schaumburg, IL 60173. Toll-free: 866-503-7546. Website: https://www.aad.org (accessed March 31, 2016).
Centers for Disease Control and Prevention. 1600 Clifton Rd., Atlanta, GA 30333. Toll-free: 800-311-3435. Website: http://www.cdc.gov (accessed March 31, 2016).
* microbes (MY-krobes) are microscopic living organisms, such as bacteria, viruses, and fungi.
* immune system (im-YOON SIStem) is the system of the body composed of specialized cells and the substances they produce that helps protect the body against disease-causing germs.
* chemotherapy (KEE-mo-THER-apee) is the treatment of cancer with powerful drugs that kill cancer cells.
* AIDS or acquired immunodeficiency (ih-myoo-no-dih-FIH-shensee) syndrome is an infection that severely weakens the immune system; it is caused by the human immunodeficiency virus (HIV).
* diabetes (dye-uh-BEE-teez) is a condition in which the body's pancreas does not produce enough insulin or the body cannot use the insulin it makes effectively, resulting in increased levels of sugar in the blood. This can lead to increased urination, dehydration, weight loss, weakness, and a number of other symptoms and complications related to chemical imbalances within the body.
* autoimmune disease is a disease in which the body's immune system attacks healthy cells.
* chronic (KRAH-nik) lasting a long time or recurring frequently.
* sinuses (SY-nuh-ses) are hollow, airfilled cavities in the facial bones.
* spores are a temporarily inactive form of a germ enclosed in a protective shell.
* pneumonia (nu-MO-nyah) is inflammation of the lungs.
* sputum (SPYOO-tum) is a substance that contains mucus and other matter coughed out from the lungs, bronchi, and trachea.
* pulmonary refers to the lungs.
* feces (FEE-seez) is the excreted waste from the gastrointestinal tract.
* liver is a large organ located beneath the ribs on the right side of the body. The liver performs numerous digestive and chemical functions essential for health.
* spleen is an organ in the upper left part of the abdomen that stores and filters blood. As part of the immune system, the spleen also plays a role in fighting infection.
* boils are skin abscesses, or collections of pus in the skin.
* ulcerate means to become eroded by infection, inflammation, or irritation.
* endemic (en-DEH-mik) describes a disease or condition that is present in a population or geographic area at all times.
* culture (KUL-chur) is a test in which a sample of fluid or tissue from the body is placed in a dish containing material that supports the growth of certain organisms. Typically, within days, the organisms will grow and can be identified.
* ultraviolet light is a wavelength of light beyond visible light; on the spectrum of light, it falls between the violet end of visible light and x-rays.
* cerebrospinal fluid (seh-ree-bro- SPY-nuhl) is the fluid that surrounds the brain and spinal cord.
* intravenous (in-tra-VEE-nus) means within or through a vein. For example, medications, fluid, or other substances can be given through a needle or soft tube inserted through the skin's surface directly into a vein.