First such study in decades strengthens public health response, informs vaccine design
RESEARCH TO WATCH
What's the study: University of Michigan researchers will determine how much of the population still lacks immunity to valley fever, a fungal infection caused by inhalation of spores that can be carried through the air in the dust of dry soils.
Why it matters: Valley fever cases have climbed sharply across the arid West, and its range and case numbers are expanding. The number of valley fever cases in the U.S. has surged from about 2,800 cases in 2000 to more than 20,000 in 2023, with California reporting about 12,500 cases. The fungus that causes valley fever is expanding beyond its traditional geographic area in the Southwest, mainly Arizona and California, into New Mexico, Washington, Texas and Colorado. True infection numbers are estimated to be 10 to 18 times higher due to a lack of reporting and the fact that many infected individuals experience mild or no symptoms.
Known by the medical term coccidioidomycosis, valley fever is noncontagious and can cause fever and fatigue, cough and shortness of breath, headaches, night sweats, muscle or joint aches, skin rashes and in rare cases, serious complications. About 60% of people who breathe in the spores have mild or no symptoms and recover on their own. Because symptoms mimic typical pneumonia or flu, roughly 70% of patients initially receive unnecessary antibiotics instead of antifungals. About 5% to 10% of cases develop chronic lung infections, and roughly 1.5% experience spread to skin, bones, joints or central nervous system. Because valley fever is often misdiagnosed as pneumonia and disproportionately affects populations that may not be well connected to healthcare, the infection is vastly underdiagnosed. The CDC estimates that only 1 in 33 cases are diagnosed.
Individuals who directly disturb soil, including firefighters, farmers, farmworkers, construction workers and other outdoor professions are at highest risk of Valley fever. More cases are occurring in the general public as wet winters help the fungus grow in soils and dry summers exacerbate dispersion of the spores in dust and wind. Major soil-disruption events, including wildfires and construction to support growing energy demands, further disperse the spores.
Understanding who's immune is necessary for evaluating vaccine candidates. While there is presently no vaccine for any fungal disease, there are valley fever vaccines progressing toward phase I human trials. The human trials are expected to face planning and implementation challenges without data on population immunity.
How much and for how long: $3.4 million from the National Institutes of Health will fund a five-year study to conduct the largest assessment of Valley fever immunity in decades and track the number of people who have been infected with Valley fever and developed an immune response. The funding will help researchers design more reliable lab tests and reporting and gather data that guides vaccine research and development. The project is directly supported by the National Institute of Allergy and Infectious Disease's Strategic Plan for Research to Develop a Valley Fever Vaccine.
Who's involved: Jennifer Head, the John G. Searle Assistant Professor of Epidemiology at the School of Public Health.
"Information on population immunity is essential to identify the true burden of disease of valley fever, identify the population at risk as the geographic distribution of the disease expands, and to design vaccine trials," she said. "Despite rapid disease increase and geographic expansion, surveys of naval recruits and students in 1949-51 provide the most recent estimates of population immunity for most U.S. counties within the endemic region. This is, in part, because population immunity for valley fever is difficult to measure at scale. While natural immunity against many infectious pathogens can be assessed by examining presence of antibodies in blood samples, antibodies against valley fever wane. The only tests that measure lifelong immunity to valley fever are those that measure cell-mediated immunity, such as a skin test, and these are not practical to conduct at scale. We plan to overcome this limitation by generating novel methods for robustly establishing population immunity that are feasible to conduct at scale.
"Knowing who remains susceptible would help public health agencies anticipate outbreaks as wet and dry periods extend the fungus's range into new areas where existing immunity against the disease may be low. Data on population immunity are also critical to permit evaluation of the full extent of the disease's burden and address missed diagnoses. When compared to surveillance data, data on population immunity reveal missed diagnoses. Identifying the degree of and reasons for underreporting among specific populations can enable targeting of educational campaigns on symptoms and diagnostics for the public and physicians. Such interventions can result in early intervention with antifungals and better outcomes."
