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Valley Fever

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Valley Fever

The incidence of coccidioidomycosis, commonly known as Valley fever, has increased over the past 20 years in California.

Valley fever is caused by a fungus in the soil in parts of the southwestern United States, including California. When the soil is disturbed, fungal spores can be released into the air. People and animals can become infected by breathing these spores into their lungs. Common symptoms of Valley fever are fatigue, cough, trouble breathing, fever, and chest pain. Cases are likely underdiagnosed, as symptoms are similar to many other respiratory illnesses, such as flu and COVID-19. Drought, dry soil, and other climatic changes likely enhance the release of fungal spores and increase infections. For more information, download the Valley Fever chapter. 

Coccidioides, the fungus that causes Valley fever, exists in soil and dirt. When airborne spores of the fungus are inhaled, people and animals can develop the disease. 

Process of valley fever contraction

Credit: CDPH 2022

What does the indicator show?  

Valley fever annual incidence rate, California, 2001-2022

This line graph shows the statewide incidence of Valley fever in California by year of estimated illness onset from 2001 to 2022, as the number of cases per 100,000 people.

 

Maps showing Valley fever rates in 2001 (left) and in 2022 (right) 

Map of valley fever rates in 2001 and 2022

Credit: CDPH 2023infographic that says that there was a 5 times increase in the annual incidence of Valley fever from 2001 to 2022

  • In California, the incidence of Valley fever has increased almost fivefold from 2001 to 2022. The highest number of new cases was reported in 2019. Valley fever incidence has consistently been highest in the South San Joaquin Valley (Fresno, Kern, Kings, Madera and Tulare Counties) and parts of the Central Coast (San Luis Obispo County).
  • Despite the consistently high rates in the Southern San Joaquin Valley, substantial increases have recently occurred primarily in Northern San Joaquin Valley, and in the Central and South Coast regions.

Why is this indicator important?

  • Most people have mild symptoms from Valley fever and fully recover. However, up to five percent suffer illness when the infection has spread from the lungs to the skin, bones, and central nervous system. There is currently no vaccine to prevent Valley fever.
  • Each year in California, around 80 deaths and over 1,000 hospitalizations are attributed to Valley fever. Even milder disease can affect people’s ability to work and function well.
  • Tracking the incidence and geographic distribution of Valley fever provides valuable information to inform public health decisions, particularly given projected changes in climate-related factors.

What factors influence this indicator?

  • The majority of Valley fever outbreaks are associated with dirt-disturbing work settings (such as construction), wildland firefighting, and correctional institutions.
  • Drought, dry conditions, dust storms, winds, and wildfires create favorable conditions for the fungus to proliferate and be disseminated. These are all related to climate change and are projected to increase in frequency and severity.
  • Blacks and Filipinos, males, pregnant women, older adults, people with pre-existing health conditions, and low-income groups are at increased risk for severe disease.

Additional resources:

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