Dusty Fungal Threat: Valley Fever Spreads as Conditions Change

George Thompson, MD, professor of infectious disease at UC Davis Medical Center, has been tracking the increase in coccidioidomycosis (Valley fever) and discussing the current trends and contributing factors. "We've seen a big increase in the number of cocci cases over the last two to three years. The central valley looks like there may even be a 200% increase in cases over the last year in some areas," he said. "And then we're really concerned that it's become more virulent. And what I mean by that is some of the patients really appear to have more aggressive disease."

Thompson noted that not only are there more cases, but there is also a higher incidence of severe cases. “We haven't typically had this many patients with valley fever in the ICU at one time. And we've talked with other sites in Northern California, and they're seeing the same thing. So we're concerned that not only are there more cases, but there's more severe cases,” he said.

Valley fever primarily affects the respiratory system, but in some cases, it can cause meningitis or spread to other organs. "The majority of people with valley fever have some type of respiratory illness. So some of those most severe manifestations are really bad pneumonia,” Thompson explained.

“Those are even people on the ventilator or that need assistance to oxygenate their blood. And so that's sort of the most severe pulmonary manifestation. In about 1% of people, valley fever will leave the lungs and go to some other site, skin, bone or brain and cause meningitis. And we've, we've seen more meningitis cases over the last few years as well," Thompson said.

For some patients, antifungal treatments are not effective, making treatment more difficult. "Some of those patients don't respond to any agent, and that's really a challenge for” how are we going to improve these patients?" Thompson said. In such cases, immunotherapy may be used to try to enhance the immune response.

Thompson also discussed the role of weather conditions in the spread of Valley fever, “In the soil, Coccidioides exists as sort of a mold form. And during periods of heavy precipitation, when we get a good amount of rainfall, we think it grows into a higher quantity within the soil,” Thompson said. “And then during drought conditions, every other cell dies and spores are formed. And those spores are what we breathe in for the infectious form of coccidioidomycosis.”

The increasing number of wildfires in California is another factor that may contribute to the spread of Valley fever. "Long droughts are associated with fires, of course, too. So we’re still sort of working on, are those fires related to valley fever or just coincident?” Thompson said. “But fire can create its own weather. It kind of updrafts air, and we’re concerned that those that large updraft might throw valley fever into the air and really facilitate spread into the surrounding region."