Work

Influence of Host Genetics on the Severity of Coccidioidomycosis

Year: 1999

Type: article

Abstract: ResearchCoccidioidomycosis (CM), also known as Valley fever, is caused by the dimorphic fungus Coccidioides immitis, endemic to the southwestern United States, Mexico, and Central and South America.In California before 1991, approximately 400 to 500 new cases were reported annually.During 1991 to 1994, the number of cases increased dramatically, with 1,200 new cases reported in 1991, 4,541 in 1992, and 4,137 in 1993 (1-4).C. immitis is a soil-dwelling organism that blooms after the rainy season.Infection usually occurs in the dry season, when arthroconidia become airborne and can be inhaled by the host.In California in 1991, increased rainfall following a drought allowed increased fungal proliferation, resulting in an increased rate of infection.The 1994 Northridge earthquake led to an increase in infections associated with landslides and dust clouds that aerosolized arthroconidia.Increased risk for symptomatic CM was directly proportional to time spent in the dust cloud (5).Of those infected, an estimated 60% are asymptomatic, with the only evidence of exposure being delayed-type hypersensitivity (DTH) reaction to a coccidioidal antigen skin test.Of the symptomatic patients, 90% to 99% experience only mild flulike symptoms.More severe chronic pulmonary disease or disseminated infection beyond the thoracic cavity occurs in 1% to 10% of symptomatic cases, depending on ethnicity (N.Ampel, pers.comm.).Disseminated CM is particularly devastating and usually requires lifelong antifungal treatment.Risk factors include male sex, compromised immune status, pregnancy, diabetes, advancing age, and smoking (6-9).Risk for disseminated CM seems to differ according to ethnicity (9).For example, during the 1977 windborne outbreak of CM in the nonendemic-disease region of Sacramento County, California, the rate per 100,000 of acute

Source: Emerging infectious diseases

DOI: 10.3201/eid0505.990508