Rising Tide of Dust in the US Could Mean Public Health Menace

Blowing dust and fungal spores are creating a public health problem that could be just a slice of what's to come with climate change.

Spurring regional expansion of ticks, and mosquitoes, warming temperatures are also rising ocean temperatures that stir up atmospheric turbulence. Put together drought, dust, and a fungus named Coccidioides, and there could be a lot more respiratory disease in areas where dust levels are high or increasing.

Why Be Concerned About Coccidioides?

Coccidioides is a fungus with spores that reside in the soil. The fungi cause a pneumonia-type illness called "valley fever" or "cocci."

Valley fever is caused by a soil-borne fungus, Coccidioides, native to parts of the west, and southwest, including California, Utah, Nevada, New Mexico, Arizona, and Texas. Researchers recently found the fungus in the state of Washington. California is hard hit by the fungal disease, especially in the past for migrant farmworkers who make their living in the soil and its dust.

Rising Tide of Dust in the US Could Mean Public Health Menace — *Image via CDC*

Here are some things to know about valley fever:

Valley fever is not contagious, you cannot catch it from someone else. People are infected when they breathe in fungal spores of Coccidioides. Of those infected with it, only about half will experience symptoms.
Symptoms are flu-like, and include headache, sweats, cough, fever, fatigue, rash, aches, and difficulty breathing. The symptoms are similar to other common infections, which causes many people suffering valley fever to delay getting diagnosed.
Treatment of valley fever involves anti-fungal medications, but the infection may clear on its own over several weeks or months of time.
While most recover, about five to 10% of people suffer lifelong respiratory damage. About 1% of those infected experience serious fungal infections in other parts of the body, including their bones, brain, and spinal cord. Meningitis is a possible complication and can be fatal.

According to the Centers for Disease Control and Prevention, 3,089 people died from valley fever between 1990 and 2008. The agency notes, on average, less than 200 die each year as a result of the infection, at present. Overall, about 10,000 people each year are diagnosed with valley fever. About 40% of those require hospitalization, at an average cost of about $50,000 each.

In areas of community or industrial growth, increased construction displaces more soil, and makes more dust, spreading the spore among housing and other commercial developments. In an article in The Atlantic, the head of the division of preventative medicine and public health at the University of California, noted, "you just have to inhale one spore. The risks of getting a face full of this stuff all depends on where you are, what the climate is."

Dust, Microbes, and Disease

No one knows exactly why valley fever is on the rise, but it could partially be climate related.

In a study published in the journal Geophysical Research Letters, researchers from the National Oceanic and Atmospheric Administration showed a parallel increase in dust storms and in the diagnosis of valley fever. The study found data-driven evidence, between 1988 and 2011, that dust storms are increasing in frequency and intensity over the American southwest. The number of dust storms each year rose from an about 20 per year in the 1990s to about 48 in the 2000s.

The study looked at the rise in ocean temperatures caused by climate change as background for the increased ferocity of dust storms in the American southwest. Increasing ocean surface temperatures push drier winds into already dry areas in the region, and block the warmer, moisture-laden tropical air flows, factors that dry soil and speed wind.

With the increased frequency of dust storms that darken the landscape, reduce visibility to zero, and deposit spores wherever the wind takes them, valley fever could be as close as a drive through a new neighborhood with the windows down or getting caught in a dust storm. The authors suggest a mix of microbes and dust are driving transmission of valley fever.

Using a climate model specifically tuned to anticipated climb in greenhouse gases, a recent study published in Scientific Reports delivers gloomy news of how the future of dry regions of the US could look. The study defines factors that suggest the second half of the 21st century could see greater dust activity by using satellite, optical, and historical data:

Surface wind, landscape bareness, and precipitation combine to increase the likelihood and variability of dust storm events.
Changes in land use can also impact the intensity and frequency of dust events.
Increased frequency of dust events in the southern Great Plains during the late summer seasons may amplify dry, dusty conditions such as those experienced during the Dust Bowl.
The model projects "an overall dustier future," with a "worst-case scenario of severe droughts and resultant dust activities."

For people working and living in regions prone to dryness and drought, valley fever is a concern. As with many diseases, some people are more vulnerable to valley fever than others, including:

People who are over age 60.
Individuals who are chronically ill, or those who are immune-compromised, including pregnant women (especially those in their third trimester).
African Americans and Filipinos are also more susceptible to valley fever. It is unclear why there are racial differences in infectious vulnerability, but genetics are thought to be at the bottom of it.

For more susceptible individuals, avoiding activities that involve excavation and disruption of surface soil could be helpful. Still, many types of people remain exposed to the potentially serious respiratory disease — farmworkers, border patrols, military personnel, and anyone routinely moving earth, including archaeologists and backhoe drivers.

Recently, the US Food and Drug Administration fast-tracked a new anti-fungal medication expected to have higher potency than existing medications for those infected by valley fever.

While there is no vaccine, awareness of the disease could lead to earlier testing and treatment if symptoms occur. Airborne particulate is always a respiratory irritant. When the dusty particulate carries spores of valley fever, it might go beyond irritation — to infection.