What Is Valley Fever and What Are the Symptoms as Cases Rise in Southwest U.S.

Researchers are investigating a link between climate change and Valley fever, an infection caused by a fungus that lives in soil in parts of the U.S., amid an increase in cases.

What Is Valley Fever?

Valley fever is caused by the fungus Coccidioides, and usually refers to a medical condition in which the fungus enters the lungs. This fungus lives in dust and soil and has been found in southwestern and western U.S. states such as Arizona, California, Nevada, New Mexico and Utah as well as in Mexico and South America.

According to the U.S. Centers for Disease Control and Prevention (CDC), there were around 18,400 reported cases of Valley fever in the country in 2019—up from around 15,600 the year before.

The same data table shows that case reports have increased substantially since 1998, when 2,271 were recorded. There have been peaks and troughs since then, with 22,641 cases reported in 2011.

Speaking to climate change news outlet Grist earlier this month, Morgan Gorris, an Earth systems scientist at Los Alamos National Laboratory in New Mexico who has investigated the conditions in which Coccidioides thrives, said the fungus tends to prefer hot, dry places.

She then looked at how the fungus might spread in a high-emissions climate change scenario, and found that much of the western U.S. could become endemic to Valley fever by the end of the 21st century.

"Our endemic area could expand as far north as the U.S.-Canada border," Morgan told Grist.

Another researcher told the outlet they were investigating the soil temperature threshold of Coccidioides.

Is Valley Fever Contagious?

Valley fever isn't contagious and can't spread between people. But in areas where the fungus is common, it is very difficult to avoid breathing it in. The CDC notes people can try to avoid particularly dusty places as much as possible.

According to the CDC, most people who breathe in Coccidioides spores don't get sick, but some do. People who become sick with Valley fever usually get better on their own over a period of weeks or months, but others will need antifungal treatment.

Valley fever is most common in people aged 60 and over. Certain groups of people may be at higher risk of developing severe forms of the disease. These include people with weakened immune systems, pregnant women, people with diabetes and people who are black or Filipino, the CDC states.

Valley Fever Symptoms

Symptoms of Valley fever include tiredness, a cough, fever, shortness of breath, headache, night sweats, muscle or joint pain and a rash on the upper body or legs. The symptoms may appear within one to three weeks after breathing in the fungus spores.

Sometimes, the fungus may also enter the skin through a cut and cause a skin infection, though this is very rare, the CDC said.

Around 5 percent to 10 percent of people who catch Valley fever will get a serious or long-term lung problem. In around 1 percent of cases, the infection spreads from the lungs to other parts of the body.