Coccidioidomycosis

escription

Coccidioidomycosis or "Valley fever" is a disease caused by the fungus Coccidioides immitis, found in the soil of disease-endemic areas. The disease is acquired by inhalation of fungal spores from dust, usually generated by human activities or natural disasters.

Occurrence

C. immitis is endemic in regions in the Americas with an arid climate, yearly rainfall 5-20 inches, hot summers, winters with few freezes, and alkaline soils. In the United States, it is found in Arizona, Southern California, New Mexico, Western Texas, and parts of Utah. Outside the United States, coccidioidomycosis is endemic in parts of Argentina, Brazil, Colombia, Guatemala, Honduras, Mexico, Nicaragua, Paraguay, and Venezuela.

Risk for Travelers

In disease-endemic areas, persons can be at increased risk for disease if they participate in or are present during ground-disturbing activities resulting in exposure to dust. These outdoor activities include construction, landscaping, mining, agriculture, archaeologic excavation, military maneuvers, and recreational pursuits (e.g., dirt biking). Natural events that result in generation of dust clouds in disease-endemic areas, such as earthquakes or windstorms, increase the risk of infection among exposed persons.

Clinical Presentation

The incubation period ranges from 7 to 21 days. Most infections (60%) are asymptomatic. Persons who have symptoms usually have a self-limited influenzalike illness characterized by fever, headache, rash, muscle aches, dry cough, weight loss, and malaise. In rare instances, severe lung disease (e.g., cavitary pneumonia) or dissemination to the central nervous system (e.g., meninges), joints, bones, and skin may develop. Persons at increased risk for severe pulmonary disease are the elderly and those with chronic medical conditions such as congestive heart failure, diabetes, chronic obstructive pulmonary disease, cancer, and corticosteroid use. Persons at increased risk for disseminated disease include African-Americans and Filipinos, those with immunocompromising conditions (e.g., HIV), and pregnant women. Diagnosis is usually made by serologic tests or culture of direct specimens. Coccidioidomycosis is not transmitted from person to person. Once infected with C. immitis, a person is immune to reinfection.

Prevention

Although complete prevention of infection is not possible, persons, especially those at increased risk for severe and disseminated disease, can decrease their risk by limiting their exposure to outdoor dust in disease-endemic areas. Dust-control measures include wetting soil before disturbing the earth or using outdoor vehicles with enclosed, air-conditioned cabs. Persons should also be advised to avoid transporting items contaminated with soil (e.g., cotton or straw) from disease-endemic areas because infections have been reported among persons who had never visited the areas but were exposed to such fomites. Wearing well-fitted dust masks capable of filtering particles as small as 0.4 µm can provide added protection for those at high risk for exposure to dust from disease-endemic areas or those at high risk for severe or disseminated disease. No effective vaccine for coccidioidomycosis is currently available.

Treatment

Most persons with acute symptomatic coccidioidomycosis do not require treatment because the illness is self-limited. Persons at increased risk for dissemination may need to receive antifungal therapy when diagnosed with acute coccidioidomycosis. All persons with disseminated disease should receive antifungal treatment. Fluconazole, which can be given orally, is generally the treatment of choice; however, those who have diffuse pneumonia or who are pregnant should be given Amphotericin B, an intravenous drug. Recommended duration of therapy varies from 3 to 6 months in those with uncomplicated respiratory infection to prolonged, sometimes lifelong, treatment in those with meningitis. An infectious diseases specialist should manage these patients.