Health
2:57 pm
Fri February 21, 2014

In California, Researchers Uncertain If Drought Will Increase Valley Fever Risk

This year, you’re likely to hear a lot of predictions about how the drought will impact our health, environment, and food.

But one thing you won’t hear is whether the dry conditions will – without a doubt - increase the risk of valley fever in California. Sure, it makes sense. Even microbiologist Antje Lauer expects that drought conditions, and drier soil, would increase the risk of valley fever.

“If we want to have less of the valley fever fungus in the soil, you would pray for more rain,” Lauer says. 

In a lab at Cal State Bakersfield, Lauer and her colleagues are studying what type of soil supports the valley fever fungus. They know this: When it’s hot and dry, the fungus makes a resilient spore, which can survive in the soil, and outlast other competitors.

“With an ongoing drought, you can hypothesize that you will have more and more areas where the valley fever fungus might occur, simply because its antagonists in the soil aren’t there anymore,” Lauer says. 

"With an ongoing drought, you can hypothesize that you will have more and more areas where the valley fever fungus might occur" - Antje Lauer

Her prediction continues: If a drought is followed up by just a little bit of rain, the valley fever fungus could start to grow in the soil, while other microbes struggle to re-establish themselves. Then, when the soil dries again, the spores can be blown into the air, and into our lungs.

Experts believe that, with the right ‘grow and blow’ conditions, valley fever may thrive after a drought.

“But this is also just hypothesis, which makes, from an ecological perspective, a lot of sense, but nobody has ever gotten any empirical data on this,” she says.

In Arizona, there’s stronger evidence of the ‘grow and blow’ hypothesis. Heidi Brown is an assistant professor of public health at The University of Arizona, who studies the effects of precipitation and temperature on valley fever.

“So you have a rain event that puts it in the soil and gets the fungus growing, then a period of drying out, and then you have this blowing and aerosolizing of spores,” Brown says. “That’s the system that we seem to see –pretty strong relationship that we’re seeing here in Arizona.”

That association doesn’t quite translate to California, and experts don’t know why. But they suspect it might have something to do with differences in soil, environment or even the susceptibility of people in the two regions.

“We’ve tried to come up with some models here in Kern County to see if some of environmental factors were predictive of increases in epidemics,” says Kirt Emery, a Kern County epidemiologist. “We have not been successful.”

In California, Emery says, the potential for a valley fever outbreak could hinge on when the rain comes after a dry spell, and when the fungus blooms.

“We really don’t know,” he says. “If the rainy season comes, in my opinion, at different times and different arenas, it will have a different effect.” 

"If the rainy season comes, in my opinion, at different times and different arenas, it will have a different effect" - Kirt Emery

For example, after a drought in the early 1990s, there was rain during the late winter and early spring, and then a big spike in cases followed. Emery thinks that season might be a critical time for watering, and then growing, the valley fever fungus.

But he can’t say for certain. That pattern doesn’t always hold up. And patient data from that outbreak is very limited.

Sometimes, other environmental factors make it hard to establish a trend. After a drought in 1976 and 1977, there was a spike of valley fever cases in 1978. That could’ve been connected to the drought or, as researchers have suggested, to a massive dust storm that was dubbed ‘The Tempest From Tehachapi.’

“Much of what I tell you are hypotheses,” he says. “They’re thoughts, they’re things we’ve pursued, and they’re ideas of scientists and researchers who have been looking at this for many years. When it comes right down to it, the answer is, what effect, we really don’t know at this point.”

Emery and other researchers say the current drought is an opportunity to learn more about the environment’s impact on valley fever. The information they glean won’t answer the question completely, but it will certainly help to unlock another piece of the puzzle.