Dust billows as a farmer plows a dry field in Kern County, California. Documented cases of Valley Fever rose 11 percent in 2018 — a preliminary total of 7,886 cases compared to 7,090 cases for the same period in 2017, according to California Department of Public Health. Photo: David McNew/Getty Images, Getty

Ted Andersen

A potentially deadly illness found in the soil and dusty winds of California’s Central Valley is on the rise, state health officials say.

Documented cases of Valley Fever rose 11 percent in 2018 — a preliminary total of 7,886 cases compared to 7,090 cases for the same period in 2017, according to the California Department of Public Health. Health officials said final data for 2018 will be available in March.

Valley Fever (coccidioidomycosis) is an illness caused by a fungus found in the soil and dirt in the Central Valley. The fungus thrives in areas of low rainfall, high summer temperatures and moderate winter temperatures. The spores are carried by the wind in dust particles when the desert soil is disturbed.

Simply passing through an area with Valley Fever and breathing in a small number of spores can lead to an infection of the lungs with flu-like symptoms. About half of the infections produce no symptoms, but in a few cases, the infection can spread from the lungs to the brain, bones, skin or eyes, causing blindness, skin abscesses, lung failure and, occasionally, death.

Kern County documented the lion’s share of California’s cases last year, with 2,771, up 17 percent from 2017 and 46 percent from 2016. In 2017, Kern County recorded nine deaths — the second-highest number since the county started keeping track of cases in 1992 and the highest number in over a decade. Kern County health officials told SFGATE they have yet to release death totals for 2018.

Other counties that recorded the most Valley Fever cases last year were Fresno (623), Tulare (425) and San Luis Obispo (340). Monterey, Contra Costa and Santa Clara counties have also seen their Valley Fever numbers more than double in recent years.

“We’ve seen a lot more cases recently,” said Michelle Rivera, a health education specialist for Fresno County. “Not all providers are testing for it so there might be more cases out there.”

Los Angeles County reported 973 cases of Valley Fever last year. Los Angeles County Public Health officials could not speculate as to the exact location of exposure, but based on environmental surveillance data and individual case reports, officials stated that the disease is also endemic to Los Angeles County soil.

Statewide, the number of reported cases quintupled from about 816 cases in 2000 to more than 4,000 cases in 2012. During that period, a total of 1,098 death records listed coccidioidomycosis as a cause, averaging 78 deaths annually, according to state public health data. Since then, Valley Fever cases have continued to trend up and state health officials have yet to pinpoint the exact cause.

Valley Fever made headlines in 2018 when, on Feb. 1, a U.S. appeals court threw out inmates’ lawsuits and ruled that California prison inmates cannot hold state officials liable for contracting Valley Fever. Ian Wallach, an attorney for some of the inmates, said the ruling was devastating.

“The families of over 40 inmates who died and 100 who got infected and require lifetime medical care are left to fend for themselves,” Wallach told the Associated Press.

Possible contributing factors include heavy rainfall after years of drought, as well as other climatic and environmental factors, increased number of susceptible people in areas where the fungus is present, and increased awareness, testing and diagnosis by health care providers.

Since the areas with the highest rates of Valley Fever are found along swaths of both Interstate 5 and Highway 101, drivers should be mindful of gusty conditions.

“While driving through these areas, drivers could keep car windows shut and use ‘recirculating’ air conditioning to reduce the risk of Valley Fever,” said Corey Egel, assistant deputy director of public affairs for the California Department of Public Health.

It’s unknown if or how the relatively dry 2017-18 winter in California will impact the number of Valley Fever cases this year, but researchers such Ian McHardy, co-director of the Center for Valley Fever at UC Davis, are cautious that the relatively wet winter California has experienced so far may portend higher numbers of incident cases — both human and animal — between the months of May and December 2019.

“There is concern that we’ll see another record number of cases in California this year,” McHardy said.