By Stan Deresinski, MD, FACP, FIDSA

Clinical Professor of Medicine, Stanford University

Dr. Deresinski reports no financial relationships relevant to this field of study.

SYNOPSIS: Cases of coccidioidomycosis significantly increased in 2016.

SOURCE: Cooksey GS, Nguyen A, Knutson K, et al. Notes from the Field: Increase in coccidioidomycosis — California, 2016. MMWR Morb Mortal Wkly Rep 2017;66:833-834.

All but approximately 3% of cases of coccidioidomycosis in the United States are reported in the states of Arizona and California, and the number reported generally has increased, with some fluctuations, in both states over the last two decades. (See Figure.) In California during that time, a peak incidence of 13.8 per 100,000 population was reached in 2011, followed by decrease through 2014. This was followed by a small increase in 2015 and then approached the previous record peak in 2016 when the reported incidence was 3.7 per 100,000 population, with the total of 5,372 cases the highest ever.

Most cases were reported from the Central Valley and Central Coast regions, especially in counties known to be highly endemic, with Kern County, whose major city is Bakersfield, alone accounting for 42% of total cases. While the incidence rate in 2016 was highest in individuals 40 to 59 years of age, those younger than 20 years of age experienced the greatest increase in incidence relative to the previous year at 134%. Males were affected more frequently than females; there was too much missing data to allow reporting of the incidence by race or ethnicity.


The cause of the observed 2016 spike in reported cases of coccidioidomycosis is unknown. Most suspect, however, were the heavy rains in that year following several years of drought. Such conditions may be optimal for the proliferation of fungus in the soil, which, with disruption by wind or human activity, results in airborne dissemination of disarticulated arthroconidia, which then may be inhaled.

Currently, early steps have been taken to construct a high-speed rail system from the San Francisco Bay Area through the middle of the Central Valley to Los Angeles. It can be predicted that many of the workers constructing this system through the most highly endemic area will acquire coccidioidomycosis.


Figure. Number of Coccidioidomycosis Cases and Incidence Rate, by Estimated Year of Illness Onset* — California, 1995-2016

Cases and incidence rate

*Estimated year of illness onset was extracted from the closest date to the time when symptoms first appeared for each patient.

Source: Centers for Disease Control and Prevention.