Emergence of Coccidioidomycosis in Washington State
February 09 2015
Coccidioidomycosis, also called “Valley Fever,” is endemic to the southwestern United States and parts of Mexico and Central and South America. Thousands of cases are reported each year in the U.S., mostly from Arizona and California. Recently, coccidioidomycosis cases have been recognized in Washington State, far north of Coccidioides’ known geographic range. Epidemiologic and laboratory data, including whole genome sequencing results, indicate that several cases were acquired in south-central Washington.
The first three coccidioidomycosis cases attributed to exposures in Washington are described in the publication by Marsden-Haug (2013) in Clinical Infectious Diseases (CID).1 The first identified case occurred in June 2010 in a 12-year-old male whose only travel outside of the Pacific Northwest was to Santa Maria, California two years before his illness. He presented with chest pain and was initially hospitalized for bacterial pneumonia, but Coccidioides was cultured from his pleural fluid upon re-admission. In July 2010, a 15-year-old male sustained knee lacerations during an all-terrain vehicle (ATV) accident in south-central Washington and developed primary cutaneous coccidioidomycosis at the injury site. The third case described in the CID report was in a 58-year-old construction worker who developed culture-confirmed coccidioidal pneumonia in May 2011 which progressed to meningitis in March 2012. His only travel to known endemic areas was a plane change in Arizona three to five years before his illness.
During the initial investigation into these three cases, 22 soil samples were collected from two of the likely exposure locations.2 In August 2013, a novel polymerase-chain reaction (PCR) test developed by the Translational Genomics Research Institute in Flagstaff, Arizona was used by CDC to demonstrate presence of Coccidioides DNA in six of the samples. Furthermore, 15 isolates of C. immitis were recovered from four of those samples using modified yeast extract medium .2 As described in a new report by Litvintseva (2015) in CID, whole-genome sequencing (WGS) revealed that the Washington C. immitis isolates represented a distinct phylogenetic clade but were more closely related to strains from California’s San Joaquin Valley than to a strain from San Diego.3 In addition, WGS showed that the clinical isolate from the 2010 case of cutaneous coccidioidomycosis was genetically indistinguishable from soil isolates from the patient’s ATV crash site, directly linking the infection with the environmental source.3
The reasons for the apparent emergence of Coccidioides far outside its known range are not entirely clear but could represent sporadic environmental distribution of the organism or under-recognition of the disease.3 Retrospective analyses of coccidioidomycosis cases in animals further support the hypothesis that Coccidioides has been established in Washington for some time.1 It is possible that climate change, extreme weather events, or rodent-mediated dispersal played a role in Coccidioides’ expansion into Washington.1,3Additional human, animal, and environmental testing is needed to understand the full extent of the endemic areas and guide appropriate educational and awareness efforts for clinicians and the public.
1. Marsden-Haug N, Goldoft M, Ralston C, et al. Coccidioidomycosis acquired in Washington State. Clin Infect Dis 2013;56:847-50.
2. Marsden-Haug N, Hill H, Litvintseva AP, et al. Notes from the Field: Coccidioides immitis Identified in Soil Outside of Its Known Range - Washington, 2013. MMWR 2014;63:450.
3. Litvintseva AP, Marsden-Haug N, Hurst S, et al. Valley Fever: Finding New Places for an Old Disease: Coccidioides immitis Found in Washington State Soil Associated With Recent Human Infection. Clin Infect Dis 2015;60:e1-3.
Kaitlin Benedict, MPH, Mycotic Diseases Branch, CDC