The epidemic seems to be a warning, for reasons that are not
clear, but the marked increase in incidence from the 1980s to 1991 through 1993 is indisputable. What factors may account
for this increase? One major consideration is the weather. C. E. Smith observed years ago that the number of cases of coccidioidomycosis
was higher in the summer after a rainy winter than after a dry winter. In March 1991, a 5-year drought in California ended
with a heavy rainfall. Rainfall was also heavy in the winters of 1992 and 1993. Though the relationship between the weather
and the density of C. immitis in the soil may never be understood in detail, the following scenario seems plausible. During
drought years, the number of organisms competing with C. immitis decreases. C. immitis does not thrive, but it remains viable
though dormant. After heavy rain, the arthrocondia germinate and multiply to a higher density than usual because of the lack
of competing organisms. Once the soil dries in the late summer and fall, the arthroconidia become airborne and potentially
Another reason for the sudden increase in disease incidence
might have been the number of susceptible persons in the disease-endemic area. The number may have been the result of both
increased migration of susceptible persons and decreased immunity in the indigenous population. Immunity comes from prior
infection and is manifest as a positive coccidioidin skin test. In almost all cases, coccidioidomycosis confers lifelong immunity. As a result of years of low incidence, the number of nonimmune persons may have increased, as evidenced by the decrease in prevalence of positive coccidioidin skin tests among local high school students. In 1939, 50% to 60% of high school students in the San Joaquin Valley had positive skin tests, but in the 1980s only 3% to 5% of high school students had positive skin tests (T. Larwood, pers. comm.). Given the historical data, this estimate seems low, but another study also found a low prevalence. In 1985, workers in Tucson estimated that 30% of a random sample of persons in a Hispanic neighborhood had positive skin tests
. In addition to the drought, irrigation of fields, the increasing amount of land under cultivation, and a decrease in indoor
dust due to the widespread use of air conditioning may also have played a role in the relatively low incidence of infections
in the 1980s.
Arizona Department of Health Services
Infectious Disease Epidemiology - Valley Fever in Arizona
The reported number of cases of Valley Fever in Arizona has been increasing since it became laboratory-reportable in 1997. In 2005 there were 3515 cases reported; only 958 cases were reported in 1997. Between January and April 2006, ADHS received over 2,000 case reports of Valley Fever. This is more than three times the five-year average for these months.
The highest rates of infection in Arizona occur in Maricopa, Pima and Pinal counties, and the peak seasons occur from June through August and from October through November.
CDC - Reemerging Infectious Disease
The risk for disseminated coccidioidomycosis is much higher among some ethnic groups, particularly African-Americans and Filipinos. In these ethnic groups, the risk for disseminated coccidioidomycosis is tenfold that of the general population . Presumably, a gene (or genes) that increases susceptibility to infection is more prevalent in these ethnic groups than in the general population. Such a resistance gene has been identified in mice, but not yet in humans. The mechanism by which the resistance genes affect the course of the disease in mice is not clear. Pregnant women and the immunosuppressed are also at high risk for developing disseminated disease (Figure 3). One study demonstrated that the growth rate of spherules was influenced by human sex hormones, which may partially account for the increased risk of disseminated disease in pregnancy. Pregnancy also redirects the immune response toward humeral (TH2) immunity and away from delayed hypersensitivity (TH1), which may influence resolution of coccidioidomycosis. Generalized suppression of cell mediated immunity also increases the risk of disseminated disease. Coccidioidomycosis is particularly severe in patients with organ transplants or AIDS.
Coccidioidomycosis in Solid Organ
Coccidioidomycosis is an endemic fungal infection of the southwestern United States. Normally a self-limited infection in healthy hosts, coccidioidomycosis can become a serious complication in patients who have had solid organ transplantation. Among patients whose solid organ transplantation was complicated by coccidioidomycosis, the infection has a variety of clinical presentations. Disseminated disease is common and has substantial morbidity. Patients at risk for coccidioidal infection should be identified so that antifungal prophylactic therapy can be initiated. Treatment options include amphotericin B or azoles. Secondary prophylaxis is recommended because relapse is frequent.
Karger Report - Viral Meningitis (.pdf)
Viral Meningitis-Associated Hospitalizations in the United States, 1988-1999; We used the National Hospital Discharge Survey and the Nationwide Inpatient Sample of the Health Care Cost and Utilization Project to estimate disease burden associated with viral meningitis hospitalizations in the United States. During 1988-1999, viral meningitis accounted for an estimated 434,000 hospitalizations (annual average, 36,000; average annual hospitalization rate, 14/100,000), and 2.1 million hospital days (annual average, 175,000). The estimated mean charge for viral meningitis-associated hospitalization during 1993-1997 varied between USD 6,562 and 8,313, resulting in annual estimated hospitalization costs between USD 234 and 310 million and a total estimated cost of nearly USD 1.3 billion for the 5-year period. In summary, viral meningitis remains an important cause of morbidity and financial burden and merits efforts to improve diagnostic, treatment, and prevention options.