SALT LAKE CITY — A little-understood disease is on the rise in the nation's Southwest, leaving a few unlucky people with serious illness, including pneumonia and meningitis.

It's a fungus called Coccidioides immitis, which causes valley fever, a flu-like illness. Though most don't even know they have it, valley fever can lead to dangerous complications for some with compromised immune systems or people who have not had the disease treated.

It's native to the soils of arid areas of the U.S. like California, Arizona and Southwest Utah. People get the disease by inhaling the fungus.

Rates of infection have skyrocketed in some parts of the country. Nationwide, the number of cases has gone up 900 percent since 1998, according to the Centers for Disease Control. Prisons in California, where the disease runs rampant, have called the disease an epidemic.

"What's really interesting ... is that the number of cases — the incidence of these cases — increased steadily throughout this time period, and really accelerated over the last few years," Benjamin Park, a medical officer at the CDC, told NPR news.

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Fortunately for Utahns, the number of cases in the state has not seen the kind of dramatic increase of infections that other states have, according to the Utah Department of Health, averaging at about 50 cases each year.

"We haven't seen the dramatic increases that have been reported in California and Arizona in the last 10 years," said Theron Jeppson, an epidemiologist with the Utah Department of Health.

Jeppson said it's possible that more awareness of the disease on the part of doctors and patients may be contributing to the rise in cases in other Southwestern states, as well as increased construction and an influx of new residents. Any disturbance to soil where the fungus is endemic increases the risk, meaning that new construction on undisturbed soil might be contributing.

Jeppson said that about 60 percent of infected individuals show no symptoms at all, but another 35 to 40 percent show mild symptoms. A rare few can experience severe pneumonia. If the disease spreads past the lungs to other tissues, victims can get meningitis or rashes.

That's what happened to California winemaker Todd Schaefer, who told NPR that it took doctors months to diagnose him with the disease after he sought treatment for the flu.

"I think if they had caught it early, it would not have been allowed to disseminate through my body and set up shop in my brain and spinal cord," Schaefer said. "That's the killer right there."

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Jeppson said that people who work outside and people going to Southwest Utah for recreational activities like biking or hiking are at the highest risk. Even gardening could lead to an infection.

If people who have recently been in the area get sick and don't receive another diagnosis from their doctor, he encouraged people to ask their doctor for a valley fever test.

"Maybe we have a large number of cases that go undiagnosed or misdiagnosed because doctors don't know to look for it," Jeppesen said. "Just because it's not a big concern in Utah, it's not necessarily something they look for."

Despite not having an epidemic on our hands, epidemiologists in Utah are keeping an eye on the disease, and follow up with everyone who gets the disease so they can see where and how it is spreading.

"It's one of the diseases that we have as a reportable disease condition in Utah and that's so we can closely monitor how much of it we get."

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