Valley fever, a fungal infection described as California’s “silent epidemic,” killed thousands of state prison inmate in 2013 and has infected tens of thousands more people in California, Arizona and other parts of the Southwest.

Still, many doctors fail to diagnose the disease until it's done serious damage — it may have left you blind or disfigured or become so entrenched in your body that you have to take medication for it the rest of your life. In some cases, it can kill you.

A stealthy, dust-borne danger

Valley fever, or coccidioidomycosis, is caused by breathing in dust that contains the spores of a certain type of fungus. That fungus thrives in the arid desert soil of the southwestern United States and parts of Mexico and Latin American. The dustier the environment, the more likely you’ll breathe in the spores. You’re at greater risk for the disease if you’re exposed to dust storms, construction, farms or earthquakes.

Related: How to Survive a Dust Storm

If you inhale the spores, you may not develop any symptoms — about 40 percent of people infected don’t. Or you may develop symptoms you mistake for the flu, such as fever, cough, chest pain, chills, night sweats, headache, fatigue or joint aches. You may also develop a painful red, bumpy rash, according to the Mayo Clinic.

In people with a weak immune system the spores can grow unchecked, setting off a chain of inflammatory responses in the lungs that causes a type of chronic pneumonia, according to the Mayo Clinic. It’s marked by cough, slight fever, chest pain, bloody sputum and nodules in the lungs.

In 1 in 100 people who get valley fever, the infection spreads from the lungs and invades other parts of the body. If this happens, the spores will likely lurk in your body forever, so you may have to take anti-fungal drugs for the rest of your life. Symptoms of this form of the disease, known as disseminated coccidioidomycosis, include disfiguring nodules, ulcers and other skin sores, painful lesions in the spine, swollen joints and meningitis, a serious infection of the brain and spinal cord membranes.

Valley fever can even lead to death. According to research by Shira Shafir, PhD, assistant professor of epidemiology at the UCLA Fielding School of Public Health, 3,100 people died from it in the United States from 1990 to 2008.

Fortunately, valley fever is easily diagnosed with a blood test. The challenge is recognizing symptoms and getting the test. Fewer than 15 percent of patients with pneumonia-like symptoms are tested for valley fever in areas where where it is common, even though studies have indicated that up to 30 percent of pneumonias in these regions are caused by the fungus.

“If doctors don’t think of the diagnosis, they won’t order the right test,” says John Galgiani, MD, of the University of Arizona Department of Medicine and a widely recognized expert on valley fever. “It’s surprising. We really need to do a better job of getting doctors in the endemic area to think of this.” Being an assertive patient can help. Research by the Arizona Department of Health Service “showed that patients who knew about valley fever before they got sick got their diagnosis quicker than patients who didn’t know about valley fever before they got sick,” says Galgiani. “It’s simple to think they must have asked their doctor, ‘Why don’t you test me for it?’”

One problem is that most doctors who practice in affected areas such as Arizona were trained elsewhere. “So it’s a foreign disease to most of them,”, says Galgiani. “They haven’t learned to think of it.”

Also a problem are vulnerable senior “snowbirds” who may contract the disease in the sunny southwest but go to their doctor in snowy Minneapolis or Boston who won’t think of valley fever, says Galgiani, “unless you tell him you were in Arizona.”

And the rate of infection is rising. In 2011 it was 10 times as high as it was in 1998, according to the Centers for Disease Control and Prevention — a fact the agency attributes to increased travel and relocation to the Southwest and to climate changes that have ushered in more hot, dusty weather.

Related: 6 Ways Climate Change May Affect Your Health

Have a rash or flu-like symptoms? Get tested

If you live in or even visit an area where valley fever is common, you can get it. You’re most susceptible if you’re exposed to dusty, dirty conditions — if you’re an archeologist, say, or if you work in the military, construction or farming.

The disease is eminently treatable, but the best strategy is to avoid getting infected in the first place, especially if you’re in one of the groups most vulnerable to the disease. Here are some steps recommended by the CDC and doctors familiar with the disease.

Get tested. If you develop pneumonia, flu-like symptoms or a rash and you live in or have traveled to an area where valley fever is common, see a doctor and ask to be tested for it right away. Be sure to tell your doctor if you have been exposed to dust and dirt.

Don’t take any chances. If you live or have traveled to a valley fever hotspot, ask to be tested even if your only symptom is that you don’t feel well.

Avoid activities like yard work, outdoor gardening and digging if you live in an area where valley fever is common, especially if you’re in a vulnerable group.

Wear a dust mask. If you can’t avoid dust, reduce your risk by wearing a dust mask (such as an N95 respirator) in dusty environments, and shower when you come inside.

Improve air quality indoors with HEPA filters (high-efficiency particulate air filters).

Related: Why Your Vacuum Cleaner May Be Bad for your Health

Roll up the car windows and turn on air conditioning when driving through the desert and other areas affected by valley fever.

Consider preventive meds. If your doctor recommends it, take prophylactic anti-fungal medication.

Clean any skin injuries right away with soap and water, especially if they’ve been exposed to soil or dust. On rare occasions, the fungus can enter the body through breaks in the skin.

Rapid diagnosis is key. “But people can’t be diagnosed if they don’t go to the doctor,” Shafir says in a CDC podcast. “Hopefully, by making people aware of the seriousness of this disease, we can encourage people who have been living, visiting and traveling in areas where infection occurs to see their doctor if they’re not feeling well and then encourage doctors to test for the disease.”

Greg Breining is a Minnesota-based journalist who writes about science, travel and nature for national and regional magazines, including Audubon and National Geographic Traveler. His books about the natural world include Wild Shore and Paddle North.