What are fungal infections?
Fungal infections (also called mycoses) represent the invasion of tissues by one or more species of fungi. They range from superficial, localized skin conditions to deeper tissue infections to serious lung, blood (septicemia) or systemic diseases. Some fungi are opportunistic while others are pathogenic, causing disease whether the immune system is healthy or not.
Fungi are one of four major groups of microbes (bacteria, viruses, parasites, and fungi). They exist in nature in one of two forms: as unicellular yeasts or as branching filamentous molds (also may be spelled as "moulds"). There are more than 1.5 million species of fungi in the environment, but only 300 species are associated with human disease. Of these, only about 20 to 25 species are common causes of infection.
Most fungal infections occur because a person is exposed to a source of fungi such as spores on surfaces, in the air, soil, or in bird droppings. Usually, infections develop because there is a break or deficiency in the body's immune system defenses and/or the person provides the "right environment" for the fungi to grow. Anyone can have a fungal infection, but certain populations are at an increased risk of fungal infections and recurrence of infections. These include organ transplant recipients, people who have HIV/AIDS, those who are on chemotherapy or immune system suppressants, and those who have an underlying condition such as diabetes or lung disease.
Fungal infections often develop on the surface of the skin, especially within skin folds and other areas kept warm and moist by clothing and shoes. These infections typically remain confined to small areas, such as between the toes, but may spread over the skin and/or penetrate into deeper tissues. Fungal nail infections are quite common, as are infections involving mucous membranes, such as the mouth and genitals. The sinuses are prone to fungal infections in certain populations. If fungi are introduced via a break in the skin, infections can develop in deeper layers of the skin (subcutaneous tissue), muscles, connective tissue, and even bones. Infections that start in the lungs may spread to the blood and can be carried throughout the body.
Some superficial fungal infections may resolve on their own, but most serious infections require medical attention and may need to be treated for extended periods of time. Those that penetrate into the body typically increase in severity over time and, if left untreated, may cause permanent damage and in some cases may eventually cause death. A few fungal infections may be easily passed on to other people, while others typically are not contagious.
Fungal infections may be categorized by the part of the body that they affect; by how deeply they penetrate the skin, subcutaneous tissue, muscle, connective tissue, or bone; by the organism causing the infection; or by the form(s) that the fungi take. Some organisms may cause both superficial and systemic infections.