As the climate warms, the southwestern United States is experiencing increasingly severe weather whiplash, swinging from drought to flood and then back to drought. As a result, the public is hearing more about lesser-known infectious diseases, such as Valley fever.
Approximately 20,000 people attended a music festival held in Lake Buena Vista, California in May 2024. In the months that followed, at least 19 people developed Valley fever and eight were hospitalized with the infection.
The outbreak followed a dramatic increase of more than 800% in Valley fever infections in California between 2000 and 2018.
In 2023, California had the second-highest number of Valley fever infections on record, with more than 9,000 cases reported across the state. And from April 2023 to March 2024, California tentatively reported 10,593 cases, a 40 percent increase from the same period a year ago.
The Conversation US asked researchers Jennifer Head, Simon Camponuri and Alexandra Heaney, who specialize in Valley fever epidemiology, to explain what Valley fever is and what might explain its rise in recent years. did.
What is Valley fever? How is it transmitted?
Valley fever is the common name for a disease called coccidioidomycosis, an infection caused by pathogenic fungi of the genus Coccidioides. This fungus is found primarily in the dry soils of the southwestern United States and parts of Central and South America.
Once the fungi have access to water and nutrients, long, branching chains of fungi grow throughout the soil. When the soil dries, these chains fragment and form fungal spores, which become airborne when the soil is disturbed, such as by wind or digging. Inhaling airborne spores can cause respiratory infections.
Valley fever cases are typically highest in the southern San Joaquin Valley of southern California and southern Arizona, but cases are increasing outside of these regions.
Between 2000 and 2018, Valley fever case rates increased 15 times in the northern San Joaquin Valley and 8 times along the Southern California coast. And between 2014 and 2018, incidence increased more than eightfold along the central coast.
Because of this trend and the high virulence of the pathogen that causes Valley fever, Valley fever is listed as a priority pathogen by the World Health Organization. Historically, fungal infections have received little attention or resources. By creating the list, WHO hopes to stimulate activity around the pathogens on the list, including gaining more resources for research and the development of new treatments.
What are the symptoms and what should people check for?
After inhaling fungal spores from the environment, Coccidioides first infects the lungs, causing symptoms such as mild to severe cough, fever, difficulty breathing, chest pain, and fatigue.
Symptoms of Valley fever can be similar to other common respiratory infections, so it’s important to seek medical attention if symptoms persist, especially if antibiotics don’t help. is.
In California and Arizona, Valley fever causes an estimated one-third of community-acquired pneumonia, or pneumonia acquired outside a hospital setting. However, because only a small proportion of community-acquired pneumonia cases are tested, the number of Valley fever cases is likely much higher. Of the diagnosed cases, half had experienced symptoms for more than two months before being diagnosed.
In 5 to 10 percent of cases, the fungus spreads from the lungs to other parts of the body, such as the central nervous system, liver, and bones, where it can cause symptoms like meningitis and arthritis. These cases can be serious and in some cases fatal.
Antifungal treatments are available, and early diagnosis and treatment are important for a better outcome.
When should you be most worried about the year?
Valley fever cases can occur year-round, but in California, cases reported through the surveillance system increase starting in August and September, peaking in November, and increasing in January and February. tends to return to background levels.
Researchers believe patients are likely exposed to the fungus in the summer and early fall, typically one to three months before diagnosis. This delay takes into account the time between a patient being exposed, developing symptoms, and being diagnosed with the disease. On average, infections peak in the fall, but seasonal intensity and timing vary by region.
Our research shows that this seasonal surge in autumn is particularly strong following a wet winter, and that alternations of dry and wet conditions are associated with increased incidence during the autumn months. I found out that it is.
Valley fever cases in California nearly doubled after wet winters that occurred one and two years after the 2007-2009 and 2012-2015 droughts.
In 2023, a similar shift occurred in California, with an extreme drought from 2020 to 2022 followed by heavy rain in the winter of 2022 to 2023.
This transition was followed by a near-record spike in infections in 2023. The state experienced another wet winter in the 2023-2024 rainy season, further raising concerns that the high risk of Valley fever will continue into 2024.
Our research team recently developed a model to predict Valley fever cases expected to occur in California between April 2024 and March 2025. The state predicts that it will likely see another surge in cases in the fall and winter of 2024, similar to the surge in 2023.
During periods of high risk, clinicians should consider Valley fever as a potential diagnosis. This is especially true when evaluating patients presenting with Valley fever symptoms and respiratory illness who have lived, worked, or traveled to endemic or emerging regions.
We are currently working to characterize seasonal disease patterns in Arizona, which is distinct from California. This is probably because Arizona has two rainy seasons.
Are some people at greater risk than others?
People who spend time or work outdoors in areas where Valley fever is common, especially those who may be exposed to dirt and dust, are more likely to contract Valley fever.
Although healthy people are still at risk of infection, certain factors can increase the likelihood of developing severe illness from Valley fever. These include adults over the age of 60, have diabetes, HIV, or other diseases that weaken the immune system, or are pregnant.
It has also been noted that people who are Black or Filipino are at higher risk for severe disease, which may be due to increased exposure to fungal spores, underlying health conditions, inequalities in access to care, or other possible predisposing factors. may be related to.
How can I avoid getting valley fever?
People living and working in areas where the fungus has been found should avoid exposure to dust as much as possible. When it’s windy and dusty outdoors, stay indoors and close your windows and doors.
When driving in dusty areas, limit your vehicle speed, close your car windows, and allow air to circulate if possible. When working outdoors, use dust-suppression techniques, such as wetting the soil before digging to prevent dust from kicking up, and installing fencing, windbreaks, and vegetation where possible.
If you have to stir soil directly or be in a dusty environment, such as construction or gardening work, consider using an N95 mask to limit inhalation of dust.
Jennifer Head, assistant professor of epidemiology at the University of Michigan. Alexandra K. Heaney, assistant professor of climate and health epidemiology, University of California, San Diego, and Simon Camponuri, doctoral candidate in environmental health sciences, University of California, Berkeley.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
