Updated 4 p.m., Sept. 4

Cases of valley fever — a lung infection that can cause severe sickness in some people — are rising across California. And state health officials said they’re seeing an increasing number of cases of the disease reported outside the Central Valley and Central Coast areas where valley fever is traditionally most common — including cases in Bay Area residents.

In the first half of this year alone, more than 5,300 people in California have caught valley fever — including at least 19 people who contracted the disease after attending the Lightning in a Bottle music festival outside Bakersfield, according to the California Department of Public Health’s latest figures from Aug. 21. These cases “occurred among people who traveled through Kern County, California, to attend the outdoor music festival,” officials said.

Eight of the festivalgoers have been hospitalized with the condition, which is not contagious. More people among the 20,000-plus attendees at the festival may have been infected with valley fever but have mistaken their symptoms for another respiratory infection. Originally, only five festival attendees were reported in late July to have the condition, but this number has now quadrupled as more people have come forward.

Jump straight to:

• What are the symptoms of valley fever?
• How dangerous is valley fever?
• What can I do to protect myself against valley fever in areas where it’s common?

While valley fever has been present in the Western U.S. for years, the frequency of cases has gone up in recent years. According to new research funded by the National Institutes of Health, the number of valley fever cases tripled between 2014 and 2018 — and then tripled again between 2018 and 2022. Overall, the infection rate has increased by 800% over the past 20 years.

“We are observing quite a bit of expansion of valley fever in California,” CDPH epidemiologist Gail Cooksey told health care professionals at a briefing last week, as reported by the San Francisco Chronicle. “Something you may not have previously thought was in your [backyard] may start to emerge in those areas.”

Climate and health experts believe that changing climate conditions are contributing to the increase, with whiplashed cycles of wet weather followed by drought creating an ideal environment for the fungus that causes valley fever to thrive. Read more about the link between valley fever and climate change.

This all means that Bay Area folks who were previously unfamiliar with valley fever — or have assumed the disease is unlikely to affect them personally — might benefit from knowing more about this condition and its symptoms. Keep reading for how to spot valley fever, who is most at risk of getting seriously sick and how to seek testing and treatment.

What is valley fever, and how do people catch it?

Valley fever is a lung infection that’s caused by a fungus called coccidioides (or “cocci”), which lives in soil in certain areas of California and the Southwestern U.S.

When soil that’s contaminated with cocci is kicked up or otherwise disturbed, infectious spores — that is, tiny particles — are released into the air and can be inhaled by people and animals. From there, cocci can enter the lungs and cause the disease known as valley fever (or coccidioidomycosis), resulting in symptoms that resemble pneumonia.

• Jump to: What are the symptoms of valley fever?

“You can get valley fever from just one breath of dust from outdoor air that contains spores of the valley fever fungus,” CDPH said. That said, the disease is “something that we think is much more common to get if you’re exposed to large amounts of dust,” said Alexandra Heaney, an assistant professor of public health at UC San Diego.

Anyone can get valley fever, but CDPH said that people who live, work, or travel in areas with high rates of valley fever are particularly at risk — especially people who are near areas where dirt and soil are stirred up, like construction, landscaping or archeological sites.

Pets can also be infected with valley fever and present different symptoms than humans.

Where am I most at risk from valley fever?

“Valley fever” itself is named for the San Joaquin Valley, where the majority of cases have historically been concentrated within California. But the disease is no longer limited to the Central Valley and Central Coast areas, where many people associate it with most. State health officials said that “more and more cases” have been recently reported in Central and Southern California.

For people in the Bay Area, travel to these areas poses a risk of contracting valley fever. In the first half of 2024, 300 cases of the disease were reported in residents of the nine-county Bay Area. In that same timeframe, 35% of all cases of valley fever in California were reported in Kern County, where the Lightning in the Bottle festival took place outside Bakersfield in May.

See the California Department of Public Health’s map of areas where valley fever has been detected.

To complicate matters when it comes to the geography of the disease, the fungus that causes valley fever can travel some distance in the air. “So even if you don’t live in the region, you still might be exposed,” Katrina Hoyer, an immunologist at UC Merced, told CalMatters.

Wildfire smoke, which can already travel huge distances and cause health complications, could also contribute to the spread of the cocci fungus. According to a 2020 paper published in the journal Science, the spores that cause valley fever can essentially hitch a ride with this smoke and travel hundreds — even thousands — of miles into areas where the disease isn’t usually common.

Is there a particular time of year I’m most at risk from valley fever?

People can get valley fever any time of the year, according to CDPH — but a person is “more likely” to be infected in the late summer and fall than at other times of the year.

“We’re going into the season for valley fever right now,” state epidemiologist Cooksey warned health professionals in mid-August — noting that it was “definitely time to watch out for increases.”

What are the symptoms of valley fever?

Not everyone who is exposed to the cocci fungus will get valley fever. But those who do can get the following symptoms:

• Fatigue
• Cough
• Fever and headache
• Shortness of breath
• Night sweats
• Muscle aches or joint pain
• A rash on upper body or legs

The symptoms of valley fever can last for anywhere from a week to a few months, but health officials advise that if symptoms last for more than a week, you should contact your healthcare provider.

Is valley fever contagious if I get it?

No: Valley fever is a respiratory disease, but it isn’t contagious in the way that COVID-19 or the flu is. Other people with valley fever can’t infect you, and if you get it, you can’t infect others either.

How will I know if my symptoms are really valley fever? Is there a test?

Valley fever has a fairly long incubation period, which can cause confusion when pinpointing the source of a sickness. Symptoms don’t show up straight away — rather, they take between one and three weeks to start. Several of the symptoms of valley fever can be easily confused with COVID-19, including fever, cough, fatigue, and body aches.

All this means that “the only way to find out if you have Valley fever is to see a doctor,” CDPH said. A blood test or a skin test can be used to diagnose valley fever and is available from health care providers.

CDPH recommends that when you see a doctor, “think about any recent outdoor exposures to dirt and dust you may have had, especially if you work outdoors or have recently traveled to or through areas where valley fever is common.” You’ll also be asked if you’ve had any symptoms for more than a week.

How dangerous is valley fever, and what treatment is available?

The CDC said that many people who get sick with valley fever have “mild symptoms,” and they’ll “often get better without medication within a few months.”

However, some people who are at higher risk for severe disease from valley fever (see below) should seek treatment to make sure their infection doesn’t get worse. Currently, this treatment is a three- to six-month course of oral antifungal medication like fluconazole.

“Rarely,” valley fever can result in severe lung infections or infections throughout the body, according to the CDC. The agency said that around 5%–10% of people who get valley fever will develop “serious or long-term problems in their lungs,” and in around 1% of cases, the valley fever infection can spread from the lungs to elsewhere in the body, including the brain and nervous system, skin or bones.

In “extremely rare cases,” the agency said, the spores from the cocci fungus can enter your skin through a cut or even a splinter and cause an infection that way.

Who’s most at risk of developing severe disease from valley fever?

CDPH said these groups include:

• Older adults (60+ years old)
• People who are Black or Filipino
• Pregnant people, especially in the later stages of pregnancy
• People with diabetes
• People with health conditions that weaken the immune system, such as cancer, HIV, autoimmune illnesses, treatment with medications that affect the immune system like chemotherapy and steroids, and organ transplant recipients.

What can I do to lower my risk of getting valley fever?

There currently is no vaccine against valley fever, according to the CDC, but “scientists are continuing to work on a vaccine to prevent valley fever with minimal side effects.”

Moreover, the CDC acknowledges that it’s “very difficult” to avoid breathing in this type of fungus “in areas where it lives in the environment.”

When you’re driving through an area where valley fever is common:

CDPH advised that you keep all car windows closed and use the “recirculating air” button in your car if you have one (it’s the button with the symbol of a car with a looping arrow inside it.)

When your recirculating air is on, your car will stop taking in any air from the outside — and instead, your AC will recirculate the air that’s already inside your car. This will help prevent dust carrying this fungus from entering your car while still keeping the inside of your car cool.

If you’re visiting where valley fever is common and there’s a lot of dust around:

Locations like construction and excavation sites can pose more risk, as the cocci fungal spores can travel into the air when dust is kicked up. The CDC said that if you can’t avoid these areas outright, you should wear a fitted N95 mask and stay inside during dust storms.

The agency also recommended using air filtration or air conditioning indoors and avoiding activities like gardening that involve “contact with soil.” UC San Diego’s Heaney noted that when activities like gardening or construction are unavoidable, “wetting down soil before doing any of that disruption can help prevent the emission of dust” and help reduce your valley fever risks.

KQED’s Katie DeBenedetti and Riley Cooke contributed to this story