Coccidioidomycosis, also known as Valley Fever, is a disease caused by the fungus Coccidioides. The fungus grows in the soil in very dry areas. Coccidioidomycosis is endemic (native and common) in the southwestern United States, the Central Valley of California, Mexico, and parts of Central and South America [CDC 2013a]. About 150,000 new infections have been estimated to occur each year in the United States [Galgiani et al. 2005] but only about 22,000 cases were reported in 2011 in the United States. This suggests that the disease is greatly underreported [CDC 2013b]. The apparent incidence of reported coccidioidomycosis increased from 1998 to 2011, from 5.3 cases per 100,000 population in the endemic area (Arizona, California, Nevada, New Mexico, and Utah) in 1998 to 42.6 cases per 100,000 in 2011, although concern has been expressed that some of this increase might be related to changes in surveillance definitions, laboratory practices, and increased awareness leading to increased testing for the disease [CDC 2013b].
Coccidioides is found in soil, commonly about 2–12 inches beneath the surface [Pappagianis 1988; Fisher et al. 2000]. The organisms can be irregularly distributed within a given area. The fungus forms arthrospores, or spores, that can get into the air and travel over long distances when soil is disturbed naturally, such as by wind, or when it is disturbed by human activities such as construction. People can get coccidioidomycosis after inhaling the airborne spores [CDC 2013a]. It has been suggested that human illness could be caused by a single spore [Pappagianis 1988; Galgiani 1993]. The infection cannot be spread from to person to person, or from animals to people. Most people who get the disease live in or visit places where the fungus is in the soil and engage in activities that expose them to soil dust.
Anyone living in an endemic area can be exposed to airborne Coccidiodes spores and thus, is at risk for coccidiodomycosis. Workers in endemic areas who are exposed to dusty conditions related to soil disturbance are thought to be at higher risk for coccidioidomycosis [CDC 2013a; CDPH 2014]. Examples include:
- Agricultural workers
- Construction workers
- Archeological workers
- Military personnel/trainees
- Wildland firefighters
- Workers in mining, gas and oil extraction jobs
About 60% of the people who get coccidioidomycosis infections do not have symptoms [Chiller et al. 2003]. People who do develop symptoms may experience a flu-like illness with fever, cough, headache, rash, and muscle aches that usually resolve without treatment. Some people with severe symptoms may need treatment with anti-fungal therapy [Galgiani et al. 2013]. A small percentage of infected persons (< 1%) may develop widespread disseminated infection, meaning that the infection spreads throughout the body [Chiller et al. 2003]. People at greater risk for developing disseminated infection include people of African American and Asian (particularly Filipino) descent, pregnant women during their third trimester, and immunocompromised persons [CDC 2013a]. Coccidioidomycosis has been shown to be costly and debilitating, with nearly 75% of patients in whom the disease has been recognized missing work or school because of their illness and more than 40% requiring hospitalization [Tsang et al. 2010].
Recent NIOSH Health Hazard Evaluation
In May 2013, the Health Hazard Evaluation (HHE) Program received a request from managers on behalf of employees at two state agencies. They were concerned about exposure of over 2,800 employees to Coccidioides at two state prisons (prison A and prison B) in the Central Valley of California. We visited the prisons in June 2013, interviewed employees about their work practices and exposures, looked at the ventilation system in selected buildings, and met with prison staff to learn about their efforts to reduce dust exposures at work. We also identified laboratory-confirmed cases of coccidioidomycosis among employees from 2009–2013 using annual employee rosters and the California Department of Public Health coccidioidomycosis database. Although not part of this HHE, the Mycotic Diseases Branch in the Centers for Disease Control and Prevention is investigating exposure of prisoners at prison A and prison B to Coccidioides.
More details about the HHE can be found on the NIOSH website. Key findings included:
- Both prisons are located in very dry areas where the fungus is endemic.
- We identified 65 confirmed cases of coccidioidomycosis among prison A employees and calculated a crude average annual incidence of 1,039 cases per 100,000 employees from 2009–2013.
- We identified 38 confirmed cases among prison B employees and calculated a crude (unadjusted) average annual incidence of 511 cases per 100,000 employees from 2009–2013.
- Employees may be exposed to Coccidioides at work and outside of work, so we do not know if each confirmed case of coccidioidomycosis was due to an exposure at work or outside of work.
- Incidence among prison employees appears to be higher than in the county general adult population
- Efforts to reduce exposure to dust from prison ground sources already included wetting soil before soil-disruption activities, reducing soil disking (shallow plowing), applying a soil stabilizer (a type of soil cement), and planting grass and other vegetation. We were not able to evaluate the effectiveness of these efforts at the prisons.
General recommendations are available for preventing work-related coccidiodomycosis. (See the California Department of Public Health website). In making recommendations for this evaluation, we were faced with uncertainties because the effectiveness of these measures in reducing occupational coccidioidomycosis is unknown. We were left with many questions.
- Should soil stabilization of prison grounds be continued?
- At what wind speed should the prison yards be closed?
- Is there a role for measuring wind speed and doing environmental sampling for Coccidioides?
- When should respiratory protection be worn by employees? What type of respirator is appropriate?
NIOSH is interested in learning how workplaces in the endemic areas minimize exposures for their employees, including those at increased risk for disseminated infection. Let us know what engineering, administrative, and respiratory protection measures your workplace takes to minimize employee exposures to Coccidioides. We are particularly interested in any evaluation of effectiveness of these efforts.
Marie A. de Perio, MD; Gregory A. Burr, CIH
Dr. de Perio is a medical officer and team leader in the NIOSH Hazard Evaluations and Technical Assistance Branch in the Division of Surveillance, Hazard Evaluations and Field Studies.
Mr. Burr is an Industrial Hygiene Team Leader in the NIOSH Hazard Evaluations and Technical Assistance Branch in the Division of Surveillance, Hazard Evaluations and Field Studies.
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Centers for Disease Control and Prevention (CDC) [2013a]. Coccidioidomycosis. [http://www.cdc.gov/fungal/coccidioidomycosis/]. Date accessed: March 2014.
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