What is Valley fever? Causes, symptoms, and why cases are rising

Valley fever is a fungal infection that affects the lungs. It is caused by a fungus called Coccidioidomycosis [1].

This fungus is a dimorphic fungus, which means it is shape-shifting. In the soil, it grows as a fuzzy mold. When it’s inhaled, it transforms its shape into small, thick-walled sacs that multiply and lead to more infection.

This is a highly evolved survival mechanism for the fungus. It helps the fungus bypass human immune defenses better [1].

The Valley Fever fungus spreads through dust. It is not contagious and does not spread from person to person [2].

A young medical student called Alejandro Posadas first discovered and described Valley Fever in 1892. He made medical history with this discovery by examining skin nodules found on an Argentinian soldier [3].

Initially, the fungus was misidentified as a protozoa but after further research, scientists in the 20th century found that Valley Fever was caused by a fungus, not protozoa [3].

Valley Fever is endemic to areas with dry weather like the southwestern USA, Mexico, some regions of Central and South America [4].

There are two known species of Coccidioides: C. immitis and C. posadasii.

• C.immitis is mostly found in California, and can even be found in Arizona, Utah, and the state of Washington
• C.posadasii is found in Arizona, Utah, New Mexico, Texas, Mexico, and parts of Central and South America [4]

Number of cases

Since Valley Fever is not a notifiable disease in all states of the United States, the total number of cases is believed to be underreported [4].

Experts estimate Valley Fever cases to be 206,000 to 360,000 a year. This is a much higher number than the ~20,000 cases reported to the US CDC (Centers for Disease Control and Prevention) each year [5].

Mortality Rate

According to the US CDC, there are about 200 deaths related to coccidioidomycosis reported each year. However, public health officials estimate 700 to 1,000 deaths annually [5].

What time of the year do Valley Fever cases peak?

Valley Fever cases are often diagnosed in Fall and early Winter. This is because, even though a person may inhale the fungus during drier months (June or July), it takes 1-3 weeks for symptoms to show up [4].

The Coccidioidomycosis fungus lives in soil until construction, dust, or storms displace them into the air. Once airborne, they can be inhaled into the lungs. Once in the lungs, the fungus changes shape (bimorphic) into a round shape (spherule) in which the fungus replicates [6].

At some point, the spherule breaks and releases the fungal endospores found inside. These individual endospores continue to grow and replicate, spreading the infection. Some of these are released back into the soil, continuing the cycle [1, 6].

Symptoms of Valley Fever often resemble other respiratory illnesses, including pneumonia caused by bacteria. For this reason, it is often misdiagnosed [6].

Symptoms include:

• Dry cough
• Fatigue
• Fever
• Headache
• Difficulty breathing
• Muscle and joint pain
• A rash on the upper body or legs [6]

Symptoms often take 1-3 weeks after exposure to appear. They often resolve within a few weeks or months. Many people infected with Valley Fever may not even exhibit any symptoms [6].

While Valley Fever infections start in the lung, in some instances, they can spread to other areas, including the brain [6].

An old name for Valley Fever is desert rheumatism, due to the fever, joint pain, and skin bumps that resemble rheumatism in dry, desert-like places [6].

To diagnose Valley Fever, healthcare providers may look at medical history, review symptoms, and conduct a physical exam [7].

Recent travel history can offer insight. If Valley Fever is suspected, blood tests can help confirm it [7].

Other diagnostic tools that may be used are chest x-rays and CT-scans. A biopsy may be requested to investigate the fungal infection in the lungs [7].

Often, people with Valley Fever infections recover on their own. However, in some cases, antifungal medications may be prescribed [6].

The most common antifungal prescribed is fluconazole, which can treat all but very severe symptoms of Valley Fever [8]. More serious Valley Fever infections may be treated with stronger antifungal medications like amphotericin B and voriconazole [6, 8].

It is important to take antifungal medications only when prescribed by a licensed healthcare professional.

Most people who get Valley Fever only get it once in their lifetime. However, those with weaker immune systems are susceptible to getting infected again [9].

There is no preventive vaccine for Valley Fever. Preventive measures focus on reducing the risk of getting infected [9].

These steps include:

• Avoiding places with a lot of dust. If unavoidable, for example, if required for work, an N95 respirator mask is recommended [10]
• Wear gloves when gardening or touching soil and wash hands (and under nails) thoroughly [9]
• Stay in a closed environment when there is a dust storm [9, 10]
• Since pets like cats and dogs can also be infected, it is important to get them checked if they have symptoms of a respiratory illness. Other animals that can be infected are horses, cows and other types of cattle, coyotes, rodents, bats, and others [11]

Valley Fever is a fungal infection that mimics the common flu (influenza), pneumonia, and other respiratory diseases. Because of this, it is frequently misdiagnosed. It is found in southwestern USA and parts of South America. However, the infection is starting to spread.

The Valley Fever fungus is found in soil but dust storms, construction, and weather changes can displace it into the air, where it can be inhaled by humans, cats, dogs, cattle, and other animals.

While many people exhibit little to no symptoms of Valley Fever, some may experience more severe signs of the disease. Diagnosis can be difficult, if a healthcare provider does not suspect Valley Fever but travel history may help narrow it down.

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