Thousands of cases of Valley Fever have been reported so far this year in California, and numbers appear on track to break records.
By the end of July, 6, 761 cases had been reported in 2025, so if cases continue at the same rate, they will surpass the current record of 12,595 cases in 2024, according to California Department of Public Health data.
Newsweek has contacted the California Department of Public Health outside of regular working hours via email for comment.
Why It Matters
Since 2000, Valley Fever cases have been increasing, starting from fewer than 1,000 cases reported annually to more than 9,000 cases in 2019. The increase has prompted concern among experts and health officials, as it seems, due to the influence of climate change, cases may continue to rise in coming years.
What Is Valley Fever?
Valley Fever, also known as coccidioidomycosis or “cocci,” is a disease caused by a fungus that grows in the soil in some parts of California and other southwestern states.
It can affect both people and animals, and is spread through spores in the air that are breathed into the lungs, causing respiratory symptoms such as cough, fever, chest pain, and tiredness or exhaustion.
Given the similarity in symptoms to other respiratory diseases, such as pneumonia and even COVID, it is often misdiagnosed or undiagnosed, the Centers for Disease Control and Prevention (CDC) reported, meaning some may be given ineffective treatment or face delays in getting the right treatment.
While some people may breathe in the spores and not get sick, others are at increased risk of developing a more severe illness, although this is rare.
Pregnant women, those with compromised immune systems, those over 60, those with diabetes and those who tend to be more exposed to dirt and dust, such as construction workers, are all at higher risk.
Between 5 to 10 percent of people who get Valley Fever may develop serious or long-term problems in their lungs, while 1 percent may have an infection that spreads from the lungs to other parts of the body, such as their skin, bones, joints, or brain, according to the CDC.
Many with the disease can recover on their own in weeks or months without treatment, but some may need antifungal medication for more serious infections and may require hospitalization.
Where Are Cases The Highest?
Valley Fever gets its name from the Central (San Joaquin) Valley as that was where cases originally were the most rife in the state, although cases have been increasing more recently in other parts of the state.
The top counties for Valley Fever cases include:
- Fresno
- Madera
- San Joaquin
- Stanislaus
- Kern
- Merced
- San Luis Obispo
- Tulare
- Kinga
- Monterey
- Santa Barbara
- Ventura
As of July this year, Kern had the highest number of reported cases compared to any other county, with as many as 1,945, although this was a decrease compared to July numbers in previous years.
Fresno had 576 reported cases by July 31, a marked increases on 2024 and 2023 July numbers.
Cases in Monterey have been rising more than in any other county though, and it was the only state which saw an increase in cases of between 200 to 300 percent across 2023 to 2025.
Why Are Cases Increasing?
There are a number of factors that could be impacting the prevalence of Valley Fever fungus, including that in recent years, climate change has meant California has had higher levels of drought and rainfall.
During times of drought, when there are higher-than-usual temperatures alongside lower-than-usual rainfall, Valley Fever fungus can survive in the soil even when other microbes tend to die off due to the lack of water.
While the fungus is believed to be dormant during a drought, so less people are likely to breathe it in, when the rain returns, the fungus can start growing again and spreading spores in dust and dirt, meaning more people can be exposed.
According to the California Department of Public Health, cases of Valley Fever in the state have historically been found to be lowest during years of drought and highest in the years immediately after a drought.
As it has been predicted that California is likely to remain in a continued drought-rainfall cycle in the coming years due to climate change, prevalence of Valley Fever cases seems likely to continue increasing.
There is also concern among experts that climate change will see Valley Fever fungus spreading all along the coast up to Canada.
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