Anyone who lives, visits, or travels through the areas where the fungus grows in the soil (these areas are called endemic) may acquire Valley Fever. Military personnel who may be training in these areas are also at risk. People working in certain occupations such as construction, excavation, agricultural work, archaeological digging and other occupations which disturb soil in endemic areas may have an increased risk of exposure and disease. Persons who pursue recreational activities such as biking or driving ATVs or 4-wheel drive vehicles in the desert may also be at increased risk. Earthquakes that have occurred in endemic areas of California have also resulted in increased cases of Valley Fever. Many domestic and native animals are susceptible to the disease, including dogs, horses, cattle, sheep, burros, coyotes, rodents, bats and snakes. Dogs are especially susceptible and often need long-term therapy with anti fungal medication.
Estimates indicate that in the United States more than 4 million people live in areas where the Valley Fever fungus is prevalent (or "endemic") in the soils. About 80% of these people live in southern Arizona, which includes the Phoenix and Tucson metropolitan areas. Residents of Phoenix, Arizona and Bakersfield, California have shown positive skin-test reaction rates of 30-40%, meaning that about one-third of residents tested have had Valley Fever sometime in the past. Among those who have never had Valley Fever, the chance of infection is about three percent per year, but the longer one resides in an endemic area, the greater the risk. In the southwestern U.S., there are approximately 150,000 new infections each year.The fungal spores of Coccidioides are often found in abundance in the soil around rodent burrows, Indian ruins and burial grounds. In these settings, infections are more likely to be severe because of intensive exposure to a large number of spores. Many infections, however, occur in persons without occupational risks. Exposure to wind-storms or recently disrupted soils may increase the chances of infection. Valley Fever infections are more likely to occur during certain seasons. In Arizona, the highest prevalence of infections occurs June through July and from October through November. In California, the risk of infection is highest from June through November, without the late summer break. |
