Scientists once considered fungi plants. Now it is clear they are a distinctly different type of organism. Unable to produce their own food as plants do, fungi are opportunistic feeders and can live on decaying matter, foods and living organisms--including humans. Fungi are abundant in the environment. Tiny seed-like fungal spores float unseen in the air. Some fungi infect humans, causing disease. Surface infections such as athlete's foot and fungal nail infections are common. Fungi can also cause internal diseases called invasive fungal infections. People with weakened immune systems are particularly susceptible to invasive fungal diseases.
Aspergillosis
Aspergillus is a common fungus found in soil, decaying vegetation, insulating materials, air conditioning vents and dust. Aspergillus spores float in the air and can be inhaled into the nose and lungs. In most instances, Aspergillus spores cause no harm. However, in some people, invasive infections develop. Aspergillus can infect the lungs and form growing fungal masses called aspergillomas. The Centers for Disease Control and Prevention (CDC) advises that people with chronic lung diseases such as emphysema and tuberculosis are most commonly affected by invasive respiratory aspergillosis. In some cases, Aspergillus moves from the lungs to the bloodstream causing a widespread, life-threatening infection. Aspergillus may also invade the sinuses, although this is rare in people with a healthy immune system.
Coccidioidomycosis
Coccidioidomycosis, also called San Joaquin Fever and Valley Fever, is a fungal disease caused by Coccidioides. This fungus inhabits dry areas. Coccidioides is common in Arizona, Nevada, western Texas, central California and some areas of New Mexico. Inhalation of dust contaminated with Coccidioides spores introduces the fungus to the lungs. CDC reports 60 percent of people infected with Coccidioides have no symptoms. In those who develop symptomatic illness, headache, fever, muscle aches, cough and skin rash are common. Although most people recover from coccidioidomycosis within a few weeks, some develop a persistent lung infection or systemic invasion in which the fungi travel to and infect other parts of the body. CDC cautions that women in the last three months of pregnancy, people with weak immune systems, and those of Asian, African-American and Filipino heritage are at increased risk for these serious forms of coccidioidomycosis.
Histoplasmosis
Histoplasma capsulatum causes the fungal infection known as histoplasmosis. According to the Infectious Disease Society of America, most cases of histoplasmosis in the United States occur in the Mississippi and Ohio River valley areas. Bat and bird droppings stimulate the growth of Histoplasma capsulatum in the soil. Caves inhabited by bats, bird roosts and waste from poultry houses often harbor Histoplasma. Histoplasma spores are inhaled when digging or moving contaminated soil. CDC reports most people infected with Histoplasma capsulatum do not become ill. However, some people experience a respiratory illness characterized by a dry cough, fever, loss of appetite, muscle aches and chest pain. Uncommonly, this respiratory illness becomes chronic, causing progressive lung damage over months to years. In rare instances, Histoplasma fungi enter the bloodstream and infect other organs. This form of the disease, progressive disseminated histoplasmosis, is life-threatening and requires aggressive treatment with antifungal medicines.
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