Arizonans feeling ill from respiratory problems that seem like pneumonia or the flu might want to ask for a valley fever test.

A surge in cases of the potentially deadly respiratory disease began last year and has continued into 2019, with 4,869 cases reported to the Arizona Department of Health Services so far this year.

Numbers for the first six months of 2019 are nearly 20% higher than the same period last year, and 75% higher than the number reported through June 30, 2017.

And right now — before the monsoon rains start — is a high-risk period for breathing in one of the coccidioides fungal spores that cause valley fever, experts say.

There are several possible explanations for a rise in reported cases, but weather patterns may be part of the reason, said Dr. John Galgiani, an international valley fever expert and executive director of the University of Arizona's Valley Fever Center for Excellence.

Galgiani treats patients whose valley fever has caused skin ulcers, broken bones and meningitis.

The spores live in the soil but cause valley fever when they become dislodged by construction, wind or other soil disturbances and become airborne.

"The risk is probably tenfold higher of getting a new case of valley fever in the summer than it is in January," Galgiani said.

A "grow and blow" climate model ties a wet winter followed by a dry summer with higher-than-normal valley fever numbers. Moisture helps the fungus grow and multiply, and hot, dry summer weather allows the fungus to thrive and spread through dust. The incubation period is one to three weeks.

Detection is important because valley fever, also known by its scientific name coccidioidomycosis, can be successfully treated with antifungal medications. But if it's treated with routine antibiotics, including penicillin, the condition could get worse. Early detection can also avoid unnecessary stress, biopsies and multiple doctors' visits.

Valley fever is a potentially fatal disease and was blamed for 48 deaths in Arizona in 2017, the most recent available state data shows. Galgiani said there's evidence that valley fever deaths are underreported.

Here are five things to know about valley fever:

65% of all U.S. valley fever cases are in Arizona

If you have lived in Arizona most of your life, it's highly likely you've already had valley fever. Maricopa, Pinal and Pima counties have been dubbed a "valley fever corridor" and account for about two-thirds of valley fever cases in the U.S. Another 30% occur in California. Most of the rest occur in Nevada, Utah and New Mexico.

You may not have even known you had valley fever. Most people who get valley fever get only mild symptoms, don't seek medical attention and may not even think they are sick.

But one in three people who inhale a spore do get sick with valley fever, and it's those people who can really suffer. Valley fever disseminates in one in every 200 people who get sick. That means it goes to the bloodstream, and can infect the lungs, skin, bones, joints, spinal cord and brain.

In 2009, then-Arizona Diamondbacks outfielder Conor Jackson told The Arizona Republic that he had a cough, was sore, achy and constantly tired. He said he saw three doctors before he was diagnosed with valley fever.

"By the third inning, it felt like I had played 20 innings with an 80-pound backpack on," he said at the time. "It was brutal."

Evidence indicates once you get valley fever, you won't get it again. However, the spore can remain in the body. If a person's immune system is greatly immunocompromised, a reactivation of the disease may occur, which sometimes happens in patients with AIDS and disseminated valley fever.

Misdiagnosis is a problem

Symptoms of valley fever can be confused for other problems. Patients have reported doctors diagnosing their valley fever as lung cancer, bacterial pneumonia, flu and tuberculosis, among other conditions.

In late 2018, Phoenix-based Banner Health, the largest health system in Arizona, began a new protocol for valley fever screening. Patients who show up at any Banner facility with symptoms of pneumonia, particularly if they return after not getting better, can now expect valley fever to be considered as a diagnosis.

Banner Health began its new valley fever protocol in part because so many Arizona doctors are trained out-of-state and may not be familiar with valley fever. Also, valley fever symptoms are so similar to pneumonia that published research shows as many as 25% of Arizonans diagnosed with community-acquired pneumonia actually have valley fever.

The symptoms of valley fever often include:

Fatigue.

Cough.

Fever.

Shortness of breath.

Headache.

Night sweats.

Muscle aches.

Joint pain.

Rash on upper body or legs.

The bone and joint pain can be so bad that valley fever has also been known as "desert rheumatism."

Researchers at the University of Arizona are working to determine whether certain genetic factors may predispose people to developing the more serious, disseminated forms of valley fever.

Studies have already found higher rates of disseminated valley fever in men than in women, and in African Americans and Filipinos versus other ethnic groups. Certain blood groups — B and AB — have been identified in studies as more likely to get the disseminated version of the disease.

MORE:Summer storms are a spectacle, but the dust is hazardous to your health

Cases are rising in California, too

Valley fever got its name from the San Joaquin Valley in California, where valley fever, as in Arizona, is endemic.

Kern County, which is the California county most affected by valley fever, recorded 1,502 cases through June 30 of this year, which is up 43.87% from the same time period last year, data from the state of California shows.

Congressional action could increase attention

Valley fever is what's known as an "orphan disease," meaning fewer than 200,000 U.S. residents have it at any given time. For that reason, advocates trying to bring attention to the disease have had a hard time getting attention and funding from political leaders.

On May 21, a group of Arizona and California congressional representatives, including Rep. Kevin McCarthy, a Republican from California whose district includes Kern County, introduced the Finding Orphan-disease Remedies and Antifungal Research and Development (FORWARD) Act. The legislation's goal is to bring attention to valley fever.

Arizona members of Congress who signed on to the bill include Republican Rep. David Schweikert, Democratic Rep. Greg Stanton, Democratic Sen. Kyrsten Sinema and Republican Sen. Martha McSally.

The legislation aims to advance sustained efforts to combat valley fever, including streamlining the U.S. Food and Drug Administration approval process to establish new antifungal diagnostics, treatments and vaccines approved for use in humans.

There's no prevention, but a vaccine is in development

The University of Arizona in 2017 received a $4.8 million, four-year grant from the National Institutes of Health announced to get its delta-CPS1 vaccine against valley fever to market.

The vaccine is being developed for dogs, but it is eventually expected to also be used for humans if clinical testing proves it's safe and effective. The vaccine has already worked in mice.

A 2005 UA study published in the Journal of the American Veterinary Medical Association found that dogs in Pima and Maricopa counties had a 28% chance of becoming infected with valley fever in the first two years of life. During that time, the chance of a dog becoming ill was 6%.

Reach the reporter at Stephanie.Innes@gannett.com or at 602-444-8369. Follow her on Twitter @stephanieinnes

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