Valley fever is an emerging fungal disease within the western United States that usually causes flu-like symptoms, but also can cause serious or life-threatening complications. Analyzing data on reported cases of valley fever in California, which have increased dramatically over the past 20 years, researchers on the University of California, San Diego and the University of California, Berkeley identified seasonal patterns. that will help individuals and public health officials higher prepare. For future increase in valley fever cases. The findings even have vital implications for the way a changing climate may increase the danger of infectious diseases. The results are published.
Researchers in collaboration with the California Department of Health (CDPH) analyzed all reported cases of valley fever in California from 2000 to 2021. By comparing these to seasonal climate data, they found and identified how the disease moved seasonally in several California counties. Cycles are influenced by periods of drought. The researchers found that while most cases occurred between September and November, there have been differences in weather patterns and timing between counties and years.
“Most seasonal infectious diseases show a peak in cases each year, so we were surprised to find that there were some years during which few or no counties had a seasonal peak in valley fever cases,” said first creator Alexandra Heaney. , said Ph.D. Assistant Professor on the UC San Diego Herbert Wertheim School of Public Health and Human Longevity Science. “It made us wonder what was driving these differences in climate between years, and based on the time we looked at, we hypothesized that drought was playing a role.”
The researchers found that, on average, counties within the San Joaquin Valley and Central Coast regions had essentially the most pronounced seasonal peaks, although the peaks began within the San Joaquin Valley.
“This is valuable information for the timing of public health messaging aimed at educating the public about the symptoms of valley fever and how to protect themselves,” Haney added.
Valley fever is attributable to the spores of a soil-dwelling fungus. People contract valley fever by inhaling infectious spores which can be aerosolized when soil is disturbed by wind or human activity. Valley fever affects people who find themselves continuously exposed to airborne dust, including those that work outdoors. However, the disease isn’t contagious.
Valley fever has long been an issue within the American Southwest, however the variety of cases has skyrocketed lately, tripling from 2014-2018 and again from 2018-2022, in response to the CDPH. However, since it continues to be relatively rare, and since it causes symptoms just like other respiratory infections, including COVID-19, valley fever is usually misdiagnosed. When left untreated, the fungus may cause severe damage to the respiratory system and spread to other parts of the body resembling the skin, bones and even the brain, the latter of which could be fatal.
“Knowing when the valley fever season starts and how severe it will be can help health care practitioners know when to be on high alert for new cases,” corresponding creator Justin Remais, P. H.D., a professor on the UC Berkeley School of Public Health. “This is the first study to precisely pinpoint when the disease is most at risk in all of California's local counties, as well as places where the disease is re-emerging.”
The researchers observed that in droughts, seasonal peaks in valley fever cases are less severe. However, when the rains return, these peaks are particularly high. One hypothesis to clarify this pattern is that drought allows heat-tolerant spores to outcompete their less hardy competitors. When the rains return, the fungus is in a position to spread widely with less competition for moisture and nutrients.
Another hypothesis suggests that the links between valley fever and drought could also be on account of the consequences of drought on rodents that host the fungus. Since rodent populations decline during droughts, and since dead rodents are considered a very important source of nutrients for the fungus, it might give you the chance to survive and spread more easily under drought conditions. .
“This work is an important example of how infectious diseases are affected by climate conditions,” Heaney said. “Although drought appears to reduce valley fever cases in the short term, the net effect is an increase in cases over time, especially as we face more frequent and severe droughts due to climate change. “
People will help protect themselves from valley fever during dry and dusty periods by minimizing time outdoors and wearing face coverings that block dust. The researchers also emphasize the necessity for more thorough surveillance of the valley fever fungus, which could be difficult to detect.
The team is now expanding the scope of their evaluation to incorporate other Valley Fever hotspots within the United States.
“Arizona is a lot dustier than California and has very different climate dynamics, and about two-thirds of the cases in the United States are in Arizona, so that's where we're looking,” Haney said. Heaney said. “Understanding where, when, and under what conditions Valley fever is most common is important for public health officials, clinicians, and the public to take precautions during times of increased risk.”