Public Health Impact and Epidemiology of Valley Fever in Arizona

Background: Valley fever is an infection caused by Coccidioides spp., a fungus that is found in the soil of the southwestern United States, and parts of Mexico, Central and South America. People become infected upon inhaling fungal spores made airborne by disturbance of soil by natural or human activity. It is not contagious and cannot be transmitted from animals to humans. Two-thirds of all valley fever cases reported nationally reside in Arizona. We described the epidemiology and impact of valley fever in Arizona.

Methods: Data from the ADHS surveillance system, population-based investigations of reported cases to the ADHS surveillance system, hospital discharge database, and vital statistics database were analyzed to assess trends in the incidence of valley fever. Valley fever-associated hospitalizations were identified using ICD-9 codes.

Results: The incidence of reported valley fever increased from 73 (n=4,768) in 2008 to 255.8 (n=16,472) reported cases per 100,000 population in 2011. However, the number of reported cases of valley fever has since declined to 84.4 (n=5,624) cases per 100,000 population in 2014. In the past decade, there were approximately 12,000 hospitalizations of Arizona residents with a primary discharge diagnosis of valley fever and nearly $700 million in associated hospitalization charges.

Conclusion: The number of reported valley fever cases in Arizona has declined since 2011. Contributing factors may include laboratory testing and reporting changes as well as environmental changes that may affect fungal growth, spore formation and dispersal. Although the number of reported cases has decreased, valley fever is still one of the most frequently reported infectious diseases in Arizona. In addition, there are significant personal and economic costs due to valley fever among Arizonans in terms of duration and severity of illness and healthcare utilization and costs.