Fallowed Fields Tied to Valley Fever

California surveillance data reveal associations between land use and coccidioidomycosis incidence

September 9, 2026
3 min

The Pathologist

Overview

A population-based study in California found associations between land use and coccidioidomycosis incidence. Newly fallowed farmland and specific agricultural practices were linked to higher rates of Valley fever.

Background

Coccidioidomycosis, or Valley fever, is an infectious disease caused by inhaling spores of Coccidioides fungi. Understanding the environmental factors influencing its incidence is crucial, especially as cases have risen significantly in recent years.

Data Highlights

Year	Reported Cases
2008	1,708
2017	9,778

Key Findings

Incidence of coccidioidomycosis increased from 1,708 cases in 2008 to 9,778 in 2017.
Higher incidence was associated with larger areas of shrubland, barren ground, and grassland.
Newly fallowed land and land fallowed in the previous 4 years were linked to higher incidence.
Specific crops, such as grain and hay, were associated with higher incidence, while deciduous fruit and nut orchards were linked to lower incidence.
The study did not confirm the presence of Coccidioides in agricultural soils or dust.

Clinical Implications

The findings suggest that environmental and agricultural factors may influence the risk of coccidioidomycosis. Clinicians should consider these factors when evaluating patients with respiratory symptoms in endemic areas.

Conclusion

This study highlights the relationship between land use and coccidioidomycosis incidence, emphasizing the need for further research into environmental determinants of this disease.