Acute Respiratory Illness at the United States Air Force Academy Field Training Site: A Prospective Cohort Study

Introduction Basic cadets at the U.S. Air Force Academy's Jacks Valley training site historically experience a high burden of acute respiratory illness. While past investigations focused on identifying infectious etiologies, the potential contributions of environmental hazards and risk factors remain unexamined. This study aimed to describe the burden of respiratory pathogens and evaluate the impact of ambient air quality and aerobic fitness on the development of acute respiratory illness. Methods This prospective cohort study of basic cadets at Jacks Valley was conducted from 14–24 July 2025. Symptomatic cadets underwent nasopharyngeal swabbing for pathogen detection via multiplex polymerase chain reaction and subsequent pathogen-specific sequencing. Daily ambient particulate matter (PM) and ozone (O 3 ) levels were obtained from the Colorado Department of Public Health and Environment. Cox proportional hazards regression models evaluated associations of both acute respiratory illness and test-positive cases with demographic, environmental, and aerobic fitness factors. Results Among 1,112 basic cadets, 37.8% developed a confirmed acute respiratory illness, of whom 71.9% (303/421) tested positive for a respiratory pathogen. Rhinovirus/enterovirus predominated, accounting for 96.7% (293/303) of positive specimens with eighteen strains of rhinovirus identified. Elevated daily maximum air quality index values for O 3 (HR: 1.225, p<0.0001), PM 2.5 (HR: 1.081, p<0.0001), and PM 10 (HR: 1.013, p<0.0001) were associated with an increased hazard of acute respiratory illness. Higher fitness scores were associated with a slight reduction in acute respiratory illness hazard (HR: 0.995, p=0.0274). Exposure to higher PM 2.5 air quality index values was significantly associated with testing positive for a respiratory pathogen (HR: 1.03, p<0.001). Conclusions Basic cadets experience a high burden of viral-mediated acute respiratory illness during field training. Poor ambient air quality likely contributes to this burden and increases susceptibility to testing positive for a respiratory pathogen. Effective mitigation strategies must target both infectious transmission chains and environmental exposures.