It can affect people and dogs, Valley fever is on the rise in the Bay Area

SACRAMENTO, Calif. - State health officials are warning about a sharp rise in a potentially debilitating disease that's affecting both humans and dogs.   

Known as Valley Fever, or coccidioidomycosis, it’s caused by a fungus that grows in the soil and dirt. 

Historically, the illness has shown up more commonly in farming regions like the Central Valley and the Southwestern U.S., but cases are rising in the Bay Area and across California.

What we know:

People and animals can contract the disease when they breathe in dust that contains the Valley fever fungus. 

"This fungus usually infects the lungs and can cause respiratory symptoms including cough, fever, chest pain, and tiredness or exhaustion," the California Department of Public Health said on its website.

By the numbers:

So far this year, there have been 369 cases reported in the nine Bay Area counties, surpassing the 348 reported all of last year and 217 cases in all of 2023, according to figures compiled from the state Valley fever dashboard.

One California county, San Bernardino, saw an increase of more than 300%, with 192 cases so far this year compared with 55 in all of last year. There were 23 reported illnesses in 2023.  

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The University of California, Davis, a leading institution for Valley fever research, said last year California had a record number of cases, with almost 12,500 reported. 

In the first six months of this year, 5,500 people have been infected, according to UC Davis figures.

State figures show the cases so far this year at more than 7,613.

"Churning up the ground can release its tiny spores into the air where they can be inhaled," the university said in a news release, adding that those in the agriculture and construction industries, as well as wildland firefighters, are more susceptible. "The more frequently someone is exposed to dust, the higher their risk," researchers noted.  

Wide range of symptoms

They also explained that the illness affects people in a wide range of ways, with many who get exposed to the fungus never even getting ill, presenting challenges in diagnosing the disease. 

"The infection can look deceptively ordinary. Patients often present with cough, fever, chills or fatigue," explained Dr. George Thompson, an infectious disease physician and co-director of the UC Davis Center for Valley Fever in a news release. 

And those symptoms are often easily mistaken for pneumonia or other respiratory infections, experts explained.  

Other potential symptoms include chest pain, a rash on the upper body or legs, headaches, and muscle or joint aches, night sweats, and unexplained weight loss. 

Can be deadly 

In rare case, the disease can be deadly if it spreads to other parts of the body and infects joints, brain, skin or other organs. 

"This form of Valley fever can be very serious and fatal," state health officials explained.,

Common in animals, especially dogs 

"The fungus also doesn’t seem to care what lungs it enters. It’s common in animals, especially among dogs that like to dig," UC Davis experts said. 

Researchers said that when dogs are diagnosed with the disease, those cases can serve as an indicator of Valley fever in an area. 

"There are lots of dogs, and they don’t travel as much as people," said Dr. Jane Sykes, a UC Davis veterinarian with a specialty in infectious diseases. "They dig in soil, which puts them at risk of the disease. They’re potentially good sentinels or signs that humans might also be getting infected in a region."

The drought factor 

Climate change is being blamed as a major factor in the recent pervasive nature of the disease. 

Researchers said that drought played a role, due to how Valley fever fungus lives and grows in the soil.

"During dry conditions and drought, the Valley fever fungus can survive in the soil, even when other microbes and organisms are killed off by lack of water," state health officials explained on the CDPH’s website. "When rain returns after a drought, the Valley fever fungus can grow again, spreading spores in dirt and outdoor dust that people can breathe in, making them sick." 

Health officials noted that typically, cases dip during years of drought, and they're highest in the years immediately after a drought.

"The switch between dry conditions during a drought and rainy winters following a drought creates the right conditions for the Valley fever fungus to thrive," the CDPH explained. 

Other Valley fever facts

• The disease is not contagious.
• People can get the disease from just one breath of outdoor dust that contains spores of the Valley fever fungus.
• Getting infected is more common during the summer and fall, people can the disease any time of the year.
• While there are treatments for Valley fever, there’s currently no known cure.

In the Bay Area, Valley fever cases are up so far this year from 2023 figures. 

Bay Area Counties

                          2025        2024       2023

Alameda            81           73             37

Contra Costa   115           89            57

Marin                 5              10              4

Napa                  4               4               0

San Francisco  21             39            15

San Mateo        43            29             21 

Santa Clara      71             69            56

Solano              19             24            20

Sonoma            10            11              7

(Source: California Department of Public Health)

When Valley fever is suspected

Health experts advise those who suspect Valley fever and exhibit symptoms for more than a week, contact your healthcare provider.

"Since Valley fever symptoms are similar to those of other common illnesses, your provider may order a blood test or other tests (such as a chest x-ray) to help diagnose Valley fever," California health officials said. 

They noted that mild infections may not require treatment, with people getting better on their own.

"However, all people with symptoms should see a healthcare provider who can determine if treatment is needed," officials said. "If you are diagnosed with Valley fever, it is very important to follow the instructions given by your healthcare provider about treatment, follow-up testing, and appointments."