What’s Behind the Increasing Rates of Coccidioidomycosis in Arizona and California?

Abstract

The number of cases of symptomatic coccidioidomycosis reported in the endemic regions of California and Arizona has increased over the past two decades. In California, the southern San Joaquin Valley has seen a dramatic increase, with rates of symptomatic illness of more than 150 per 100,000 of population in Kern County. In Arizona, almost 5,000 cases are now reported yearly. In contrast to California, the coccidioidal endemic region in Arizona is also the most populous region of the state, and Arizona now accounts for 60% of all cases reported in the United States. Reasons for these increases appear to be multifactorial. Possible etiologies include climate change, changes in local exposure, an increase in the number of individuals susceptible to infection living in the endemic region, and increased testing and reporting. None of these factors are mutually exclusive and none has been clearly established as the etiology for the increase.

Coccidioidomycosis-associated Hospitalizations, California, USA, 2000–2011

“…The increase in hospitalizations is consistent with the dramatic increase in the number of reported coccidioidomycosis cases in California, yet the reasons for the increase are unclear ( 6 , 12 – 15 ). Contributing factors may include changes in climate and rainfall patterns, leading to proliferation of C. immitis fungi in the soil; soil-disturbing construction activities; an increase in susceptible persons moving to disease-endemic areas; and heightened awareness and diagnosis ( 1 , 2 , 5 , 16 , 29 ). …”

“…Over the past decade, increases in the number of reported cases of coccidioidomycosis have been documented from Arizona and California ( 6 , 12 – 16 ). In California, the rates of reported cases increased >6-fold from 2000 to 2011 (2.4 to 14.4 cases/100,000 population, respectively) ( 13 , 15 ).…”

Coccidioidomycosis: epidemiology

“…During this time, the only major change to California’s surveillance was a transition to a laboratory-based reporting system in 2010. Coccidioidomycosis incidence also rose substantially during 1998–2011 in other endemic areas (where reporting practices have remained relatively consistent), including New Mexico, Nevada, and Utah,116 perhaps indicating improved awareness of the disease, changes in testing practices, increased travel or relocation to endemic areas, and growth of the “at-risk” immunosuppressed population 117. Other hypotheses include increased spore dispersal due to environmental changes (ie, temperature, moisture) or human activity such as construction 118…”

Call for a California Coccidioidomycosis Consortium to Face the Top Ten Challenges Posed by a Recalcitrant Regional Disease

“…Some have hypothesized that the increase may be, in part, an artifact of the greater use of non-specific diagnostic tests such as the Meridian EIA test that has a high false-positivity rate for IgM antibody. Other factors for the observed changes could include improved disease awareness by patients and physicians alike, increased travel, or population growth in endemic areas, and growth of the ''at-risk'' population [12,13]. Alternative or contributory factors such as increased spore dispersal due to environmental changes (i.e., temperature, moisture) [14] or increased construction accompanying population growth within the endemic region have also been proposed as explanations [15,16].…”