COCCIDIOIDOMYCOSIS (Valley Fever)
Coccidioidomycosis, the disease caused by a pathogenic fungus called Coccidioides immitis , is also known as Valley Fever because the organism is prevalent in the San Joaquin Valley of Central California. The fungus, however, can also be reported from certain parts of the southwestern United States and norther Mexico. Some endimic regions are also found in South America.
C. immitis infections are contracted almost exclusively by the respiratory route. The clinical spectrum of disease is broad, ranging from an asymptomatic infection to a rapidly fatal mycosis. The most common clinical presentation is self-limited pneumonia, but in some cases the fungus can cause chronic cavitary pulmonary disease or disseminate beyond the lungs to the skin, bones, meninges and other body organs.
Coccidioides immitis is a primary fungal pathogen can be isolated from microbially depauperate soils of hot, semi-arid regions. Like most medically-important fungi that cause systemic disease, C. immitis demonstrates different morphologies in its saprobic and parasitic phases, but is distinguished from other fungal pathogens by the unique morphogenetic features of its growth in host tissue.
It has been estimated, primarily on the basis of skin tests, that there are between 25,000 and 100,000 new cases of human C. immitis infections each year in United States. Approximately 10 in 200 of these progress to disseminated disease. A history of recurrent epidemics of coccidioidal infections, primarily in recreational and urban areas of the San Joaquin Valley, has focused attention on the need for both improved therapy and vaccine development. A recent Tucson news report claimed a 50% increase in the number of reported C. immitis infections during 1999 in Pima County, Arizona, and a 30% rise in the disease statewide. The direct cost of medical supplies and sick leave for patients with Valley Fever has also escalated. In Kern County, California, located near the epicenter of the endemic region in that state, the accrued cost of the disease from 1991 to 1995 was estimated at more than $66 million. Vaccination of persons at risk of contacting coccidioidomycosis is a feasible approach to the control of this insidious fungal disease.
Many cases of coccidioidomycosis have also been reported in regions which are not hyperendemic, such as San Diego and Los Angeles. Outbreaks of coccidioidomycosis have occurred among archaeology students digging in prehistoric Indian sites in Northern California. In 1977, a major dust storm blew soil from the San Joaquin Valley up into Northern California, including San Francisco, Marin County, Santa Clara, and Monterey County. Immediately following the storm, numerous cases of coccidioidomycosis were reported in non-endemic regions of middle and Northern California.
