Drought raises concern about elevated risks of Valley fever


With dry conditions plaguing the western United States, UC Davis Health infectious disease experts are concerned about an increase in cases of Valley fever. The fungal infection primarily manifests as a respiratory illness and can cause fever, cough and fatigue.

George Thompson is the director of the UC Davis Center for Valley Fever.

Valley fever is caused by the fungus Coccidioides, microscopic spores which live in soil in the southwestern parts of the U.S., including California. When the ground is disturbed by wind, construction, farming or other movement, the spores become airborne. They can then be inhaled, infecting the lungs and other parts of the body via the bloodstream.

“The drought in California could play a big role in an escalation of cases of Valley fever,” said George Thompson, a UC Davis infectious diseases specialist and director of the UC Davis Center for Valley Fever. “Dry conditions cause Coccidioides to form into spores and when the wind blows, they become aerosolized, allowing them to be inhaled and infect people's lungs.”

The “Valley” in Valley fever refers to the San Joaquin Valley in California, where the disease was first linked to the fungus. In 2019, the U.S. Centers for Disease Control and Prevention (CDC) reported 7,408 cases of Valley Fever in California.

“Historically, the majority of Valley fever cases in California have been diagnosed in people who live in the San Joaquin Valley,” explained Thompson. “As one of the most productive agricultural regions in the nation, soil disruption and exposure to agricultural dust in this region are common.”

Symptoms of Valley fever include flu-like symptoms, such as cough, fever and fatigue and typically resolve without treatment. But a small number of people develop more severe cases that cause chronic pneumonia, joint infection, or meningitis.

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

“General awareness of the disease can go a long way in helping to fight it,” Thompson said. “It can take months for doctors to correctly diagnose Valley fever, and then patients can have weeks or months of continuing symptoms even with effective therapy. Diagnosing people at the time of the infection would significantly decrease the risk of the disease worsening.”

With extremely dry conditions throughout California, the CDC recommends “common-sense methods” for discouraging Valley fever infections. They include:

  • Avoid dusty areas such as excavation or construction sites. (If you can’t avoid these areas, wear an N95 respirator while you’re there.)
  • Stay inside during dust storms and close your windows.
  • Avoid activities that involve close contact to dirt or dust, including yard work, gardening, and digging.
  • Use air filtration measures indoors.
  • Clean skin injuries well with soap and water to reduce the chances of developing a skin infection, especially if the wound was exposed to dirt or dust.
  • Take preventive antifungal medication if your healthcare provider says you need it.