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Changing Climate May Expand Valley Fever’s Impact
Valley fever feeds on heat. And as the average temperature ticks up with each passing decade, experts are concerned that the fungus’ footprint and impact are expanding, as evidenced by a rise in cases in areas far outside the hot spots of the Central Valley of California.
Valley fever feeds on heat.
And as the average temperature ticks up with each passing decade, experts are concerned that the fungus’ footprint and impact are expanding, as evidenced by a rise in cases in areas far outside the hot spots of the Central Valley of California.
In the soil, the cocci fungus lives on dead organic matter. Less rainfall and higher temperatures reduce overall vegetation, diminishing soil competition for the hardy fungus, scientists say. Cocci spores survive—even thrive—when the environment is drier and hotter since other competitors die off.
Cal State Bakersfield scientists are using satellite images to map areas that could be friendly to the fungus’ growth. They’re looking for similar vegetation to what is found on Sharktooth Hill, a popular site with for digging up bones from more than 5 million years ago. Because of that digging, researchers often inhaled spores from the soil and came down with valley fever.
So when the Cal State Bakersfield team finds areas that have vegetation that mirrors Sharktooth Hill, they paint that part of the map yellow.
Their map shows large swaths of Central California bathed in yellow, mostly undeveloped areas such as those along the I-5 and Highway 99 corridors or areas that have been burned by wildfires. Areas of high vegetation or those paved over typically don’t harbor the fungus, explained Jorge Talamantes, a California State University Bakersfield physics professor.
“California is becoming dryer,” he said. “We have some climate changes. I think the environment where the fungus grows will expand.”
What Talamantes and other scientists are trying to figure out is whether the fungus itself is moving into new areas or whether it has long been there and is simply waiting for the right conditions to flourish.
Their computer mapping shows vegetation conducive to the fungus' growth farther north and east than valley fever cases normally occur. In theory, the soil near San Francisco would support the fungus’ growth, if it didn’t rain so much there. If rainfall or temperature patterns change, the reach of the fungus – and the illness – could expand farther, Cal State Bakersfield microbiologist Antje Lauer said.
Still, confirming these scientific theories would require more research funding and many more people working on the problem, she said.
The fever footprint grows
Paso Robles, a favorite spot among wine enthusiasts, tucked into the hills about 30 minutes from the Central California coast, doesn’t look like the typical valley fever zone. Bakersfield receives less than 6 inches of rain annually, making it one of the driest parts of the state. Paso Robles averaged 15 inches over the past decade and received more than 20 inches in each of the past two years.
Yet Paso Robles winemaker Todd Schaefer acquired a severe case of cocci in 2003 and has struggled since with a variety of health complications, including fungal meningitis. He was running a bulldozer through a vineyard when he breathed in the cocci spores in the dust, he believes. Over the past six months, Schaefer was only able to work two days.
"Doctors can't believe I'm still alive," he said. "They told me flat out, they can't believe it. But somehow I'm able to get by."
San Luis Obispo County, where Paso Robles is located, has seen a rise in the number of cases each year. It reported four cases of the disease in 1990, a year when only seven of 58 counties reported more than 10 cases. But by 2011, San Luis Obispo health officials reported 242 cases. Today, valley fever is rising in more than a third of the counties in California. The dramatic increase cannot be explained away as just as a sign of increasing awareness and better public health monitoring of the disease, health officials say.
Look at a map of valley fever cases over the years and it pops up in more states each year over the past decade. In 2001, nearly all cases were in the Southwest. By 2006, though, 13 states reported valley fever, including Michigan, Ohio, and Minnesota, which reported more cases than New Mexico and nearly as many cases as Nevada. Some of these cases are likely caused by travelers visiting the Southwest, but, as with everything related to valley fever, there has been very little funding of research into understanding the fungus’ reach.
Senior scientific advisor Thomas Mace is testing a theory about how weather patterns affect the fungus. His research builds on University of Arizona findings and work by Kern County health officials that show that spikes in rainfall foster the fungus’ growth – like the unusually heavy rains seen in the Central Valley in 2010. When a wet year is followed by a dry spell – like the one the Valley saw in 2011 – grasses and vegetation die off, leaving the more resilient fungus exposed and airborne.
Under that theory, a drier climate with occasional bouts of worsening storm patterns could spur more valley fever cases, turning a regional epidemic into a national one.