Valley Fever is Surging: Why Every Californian Needs to Know This Now!
California’s Valley Fever Crisis
Valley Fever in California: Essential Facts You Should Know
Cases of Valley fever tend to surge between September and November, with drought conditions temporarily dampening these peaks.
However, larger outbreaks tend to occur once rainfall returns. Valley fever, a fungal infection prevalent in the western U.S., usually manifests as flu-like symptoms but can escalate into severe or fatal complications.
Researchers at the University of California San Diego and UC Berkeley examined reported cases in California, revealing a significant rise over the past two decades.
Their findings highlight seasonal trends that could enable both individuals and public health authorities to better prepare for upcoming outbreaks.
The study sheds light on the role of climate change in amplifying the risk of infectious diseases. Published in The Lancet Regional Health – Americas, the research emphasizes the potential for changing weather patterns to worsen the spread of Valley fever.
In collaboration with the California Department of Public Health (CDPH), the researchers analyzed all reported Valley fever cases in California from 2000 to 2021.
By correlating the data with seasonal climate patterns, they uncovered the cyclical nature of the disease in different counties and noted the influence of droughts on these cycles. While most cases occur in the fall months, patterns varied across counties and years.
Public Health Implications
“We were intrigued to find that certain years showed no seasonal peak in Valley fever cases across many counties,” said lead author Alexandra Heaney, Ph.D., assistant professor at UC San Diego’s Herbert Wertheim School of Public Health. “The timing led us to hypothesize that drought could be a factor affecting these seasonal variations.”
The study revealed that counties in the San Joaquin Valley and Central Coast regions experienced the most pronounced seasonal peaks, although the San Joaquin Valley saw earlier increases. “This is critical for timing public health efforts to inform residents about Valley fever symptoms and preventive measures,” Heaney added.
Valley fever is caused by the soil-dwelling fungus Coccidioides. The disease spreads when people inhale infectious spores that become airborne through wind or human activity.
Those most at risk are individuals frequently exposed to dust, particularly outdoor workers. Valley fever, however, is not contagious.
While the disease has long been an issue in the American Southwest, case numbers have soared in recent years—tripling between 2014 and 2018, and again from 2018 to 2022, according to CDPH.
Despite this rise, the disease is often misdiagnosed due to its rarity and symptom similarity to other respiratory infections, including COVID-19. Left untreated, Valley fever can cause severe respiratory damage and may spread to the skin, bones, and brain, which can be fatal.
California’s Valley Fever Crisis: Research Insights on Drought and Disease Dynamics
“Knowing the timing and intensity of Valley fever outbreaks can alert healthcare providers to heightened risk periods,” said corresponding author Justin Remais, Ph.D., professor at UC Berkeley’s School of Public Health.
“This is the first study to pinpoint the peak risk periods across all of California’s endemic counties and regions where the disease is newly emerging.”
The research found that during drought periods, Valley fever cases tend to be less severe. However, when rains return, the peaks are particularly sharp.
One hypothesis is that droughts allow heat-resistant Coccidioides spores to outlast their competitors. Once moisture returns, the fungus thrives with fewer rivals for water and nutrients.
Another theory suggests that the relationship between Valley fever and drought stems from the impact of drought on rodent populations, which harbor the fungus.
As rodent numbers decrease during droughts, dead rodents might provide a key nutrient source for the fungus, aiding its survival and spread.
“This research illustrates how infectious diseases are intricately linked to climate conditions,” Heaney explained. “Although droughts seem to suppress Valley fever cases in the short term, over time, they contribute to a net increase, especially as climate change brings more frequent and severe droughts.”
Individuals can protect themselves by limiting outdoor exposure during dry, dusty periods and wearing masks to block airborne particles. The researchers stress the importance of better monitoring of Coccidioides, which can be difficult to detect.
The team plans to expand their research to include other U.S. regions where Valley fever is prevalent.
“Arizona’s climate is dustier than California’s and has different climate dynamics. With two-thirds of U.S. cases occurring in Arizona, our next focus will be there,” said Heaney. “Understanding the conditions that foster Valley fever outbreaks is crucial for public health officials, physicians, and communities to take necessary precautions during high-risk periods.”
Reference
“Coccidioidomycosis seasonality in California: a longitudinal surveillance study of the climate determinants and spatiotemporal variability of seasonal dynamics, 2000–2021” by Alexandra K. Heaney, Simon K. Camponuri, Jennifer R. Head, et al., 19 August 2024, The Lancet Regional Health – Americas.
DOI: 10.1016/j.lana.2024.100864
This study was funded by the National Institutes of Health (grant R01AI148336).
California’s Valley Fever Crisis
