This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Researchers at UC San Diego and UC Berkeley have found that certain landscapes surrounding California communities are associated with differing rates of Valley fever, a fungal respiratory infection caused by inhaling spores carried in windblown dust. Naturally dry, sparsely vegetated landscapes and some types of farmland were associated with higher disease rates, while other agricultural land uses were associated with lower rates.
The findings also suggest that fallowing farmland may influence Valley fever rates in some circumstances. The study was published Aug. 21, 2026, in Science Advances. "California is undergoing a major transformation of its agricultural landscape, and we need to understand how those changes may affect public health," said Alexandra Heaney, Ph.D., assistant professor at the Herbert Wertheim School of Public Health and Human Longevity Science at UC San Diego and first author of the study.
"Our findings suggest that land management decisions can have consequences that extend beyond agriculture and water use. As more land is taken out of production, we may see health risks and therefore have the opportunity to build prevention measures into how California's landscapes are managed." Valley fever is caused by Coccidioides, a fungus that grows in soil across parts of California and the southwestern United States. When soil is disturbed by wind, farming, digging or construction, tiny fungal spores can become airborne and be inhaled, making people who inhale them sick.
It's important to note that Valley fever does not spread from person to person. In California, rates of Valley fever have increased by more than 800% over the past two decades. While many people who inhale the spores never develop symptoms, those who do can experience a debilitating respiratory illness lasting weeks to months.
A small share of infections become severe, spreading beyond the lungs or causing serious long-term lung disease. The highest burden of Valley fever in California occurs in the southern San Joaquin Valley—one of the most productive agricultural regions in the world—where drought, water scarcity and groundwater regulations are driving changes in land use, including the fallowing of some farmland. To investigate how these changes may relate to disease, researchers analyzed 65,657 confirmed Valley fever cases reported to the California Department of Public Health between April 2008 and March 2021.
The cases were linked to high-resolution maps showing natural vegetation, crop types and fallowed fields across 20 California counties where Valley fever was more common. Researchers examined how land cover was associated with disease rates while accounting for factors including climate, elevation, socioeconomic conditions and employment in agriculture and construction. The researchers found that communities surrounded by greater amounts of shrubland, barren land and grassland had higher rates of Valley fever.
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