Valley fever outbreaks more widespread than previously thought

Outbreaks of coccidioidomycosis, known as valley fever, have reached beyond areas in which it was previously considered endemic, and most stem from the environment, according to researchers.

The findings show that the disease demands increased surveillance, they wrote in the CDC journal Emerging Infectious Diseases.

“Increased attention to outbreak identification and tracking is worthwhile, given the continued population growth in coccidioidomycosis-endemic areas, increased settlement at the wildland-urban interface and the incompletely understood effects of intensifying climate change on Coccidioides,” researcher Michael Freedman, MD, a pediatric resident at the Children’s Hospital of Pittsburgh, and colleagues wrote.

Valley fever is caused by Coccidioides fungi, whose spores are found in soil. Patients can be exposed to it via airborne dust. It has been known to be endemic in the American Southwest, south-central Washington, northern Mexico and other parts of Latin America. The disease causes influenza-like symptoms including cough, shortness of breath, fever and fatigue.

About 10,000 valley fever cases are reported each year in the United States. However, there are likely many more cases because it is underdiagnosed, the researchers said, citing previous research.

To identify characteristics of valley fever outbreaks, along with possible prevention strategies, Freedman and colleagues assessed studies on outbreaks occurring between 1940 and 2015. They included data on 47 outbreaks, involving 1,464 cases, in their assessment.

Forty of the outbreaks (85%) were associated with environmental exposure. Two outbreaks, accounting for 582 valley fever cases (40%), resulted from natural disasters in California — the “Tempest from Tehachapi” dust storm of 1977 and the Northridge earthquake in Ventura County in 1994, the researchers said.

Seven outbreaks were nonenvironmental, meaning they were health care or laboratory related. Of those, four outbreaks were laboratory related, two were organ transplant related and one was nosocomial.

Twenty-five outbreaks (53%) were associated with occupational exposure, the researchers said. Of those, 11 were linked to the military, seven were associated with construction and seven were related to archeology and other field studies. The researchers noted that workers who disturb soil in areas where valley fever-causing fungi are endemic are thought to have higher risks for infection.

Reports on 37 outbreaks (79%) revealed previously unknown endemicity data, the researchers said. Of those outbreaks, 12 occurred in an area not previously known to have endemic valley fever. Those areas are in Arizona, Brazil, California, Texas and Utah. Another four outbreaks confirmed suspicions of the disease’s endemicity in certain areas, which were also located in Arizona and California.

The findings indicate that health care officials and business leaders should vigilantly keep track of where valley fever outbreaks occur and under what conditions.

“Monitoring outbreaks could be critical in identifying new areas of endemicity and high-risk activities,” they wrote. “Increased awareness of coccidioidomycosis among employers of persons in potentially high-risk occupations, the public and health care providers is needed to reduce both the risk and severity of future outbreaks.” – by Joe Green

Disclosures: The authors report no relevant financial disclosures.