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Coccidioidomycosis — a Growth Industry

May 1, 2013
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By Stan Deresinski, MD, FACP, FIDSA, Clinical Professor of Medicine, Stanford University, Hospital Epidemiologist, Sequoia Hospital, Redwood City, CA, Editor of Infectious Disease Alert.

Synopsis: There was an 8-fold increase in the incidence of coccidioidomycosis in endemic states from 1998-2011 – with more to come.

Source: Centers for Disease Control and Prevention (CDC). Increase in reported coccidioidomycosis - United States, 1998-2011. MMWR 2013; 62:217-21.

Clinicians in California and Arizona have been aware of an apparent increase in their number of encounters with patients with coccidioidomycosis over the last decade and this has been confirmed in several publications. In addition to these 2 states, however, areas of endemicity exist in Nevada, New Mexico, and Utah, as well as in western Texas (but, unfortunately, coccidioidomycosis is not reportable in Texas). The CDC provides a broad picture of the changing epidemiology of coccidioidomycosis in the U.S. by analyzing data from the National Notifiable Diseases Surveillance System (NNDSS) for the years 1998–2011.

During that period, a total of 111,717 cases were reported to CDC from 28 states and the District of Columbia. Overall, the incidence of reported coccidioidomycosis increased from 5.3 per 100,000 population in the endemic area states of Arizona, California, Nevada, New Mexico, and Utah in 1998 to 42.6 per 100,000 in 2011. Of the cases, 66% were from Arizona, 31% from California, 1% from other endemic states, and <1% from states not considered endemic for this infection. Combining data from Arizona, California, Nevada, New Mexico, and Utah, it was found that the number of cases increased from 2,265 in 1998 (age-adjusted incidence rate [aIR]: 5.3 per 100,000 population) to 8,806 in 2006 (18.0 per 100,000). It has not, however, been a steady trend: there was a decreased number of cases in 2007 and 2008 followed by an increase in 2009 (12,868 cases; 25.3 per 100,000), which continued into 2010 and 2011 (42.6 per 100,000). The incidence increased in all age groups with those 40-59 years having the highest rates in California while in Arizona, this distinction was held by those >60 years of age (Figure). In 2011, the incidence of coccidioidomycosis in Arizona was 381.1 per 100,000 among persons aged 60–79 years and 385.2 per 100,000 among those persons ≥80 years of age.

FIGURE. Coccidioidomycosis incidence per 100,000 population, by age group — Arizona, California, Nevada, New Mexico, and Utah, 1998–2011

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In Arizona alone, the number of cases increased from 1474 in 1998 to 16,467 in 2011 accounting for a growth in aIR from 30.5 to 247.7 per 100,000 population — an increase of approximately 16% per year. The rate of growth was similar in California with the number of cases increasing from 719 in 1998 (aIR: 2.1 per 100,000) to 5,697 in 2011 (aIR: 14.9 per 100,000) for an average annual increase of 13%. The number of cases reported in Nevada, New Mexico, and Utah combined increased from 72 in 1998 (aIR: 1.4 per 100,000) to 237 in 2011 (aIR: 3.1 per 100,000) (p<0.001). In nonendemic states there was an increase in reported cases from 6 to 240 during the period of study.

Commentary

In 2011, coccidioidomycosis was the second most commonly reported nationally notifiable condition in Arizona and the fourth most commonly reported in California. While some of this increased incidence described by CDC may be related to improved diagnosis, it is likely that the numbers still represent an underestimate of the extent of the problem. Despite the fact that studies have shown that coccidioidomycosis may account for approximately one in 5 cases of community acquired pneumonia in urban areas of Arizona, a very large proportion of these go undiagnosed — hardly an advertisement for diagnostic acumen.1 Despite the increase in reported cases, overall U.S. coccidioidomycosis mortality rates have remained fairly stable at approximately 0.6 per 1 million person-years during 1990–20082, suggesting that the most severe life-threatening cases are being identified by clinicians and are being appropriately treated.

New foci of infection are still being identified as in the case of the description of 3 cases of coccidioidomycosis in which the infection appeared to have been acquired in eastern Washington state.3 In addition, the human population in endemic areas is expanding and, in the process, disrupting the source of Coccidioides species, the soil. The construction if Interstate 5 running the length of the central valley of California was almost disrupted as a result of a large number of cases of coccidioidomycosis in workers. California is about to begin construction on its “bullet train” system, with the first portion to be built in the San Joaquin Valley, from Merced (“Gateway to Yosemite”) to the San Fernando Valley and Los Angeles. Arizona is also considering construction of a high speed rail system. These activities will guarantee business for physicians expert in the management of coccidioidomycosis.

References

1. Chang DC, et al. Testing for coccidioidomycosis among patients with community-acquired pneumonia. Emerg Infect Dis 2008;14:1053–9.

2. Huang JY, et al. Coccidioidomycosis-associated deaths, United States, 1990–2008. Emerg Infect Dis 2012;18:1723–8.

3. Marsden-Haug N, et al. Coccidioidomycosis acquired in Washington state. Clin Infect Dis 2013;56:847-50.