Germicidal ultraviolet to reduce transmission of respiratory infections indoors: a systematic review

BACKGROUND: Respiratory infections that transmit through air contribute substantially to global morbidity and mortality. Although preclinical data on germicidal ultraviolet (GUV) for air treatment are promising, its real-world effectiveness remains incompletely understood. PURPOSE: Review effectiveness and safety of GUV for preventing respiratory infection transmission. DATA SOURCES: Medline, Embase, Global Health, Cochrane Library, CINAHL, Engineering Village, Epistemonikos, Scopus, and Environmental Science Collection from inception through December 2025. STUDY SELECTION: Studies of GUV with a comparator, measuring human outcomes including respiratory infections, absenteeism, or adverse events. DATA EXTRACTION: At least two investigators extracted data. DATA SYNTHESIS: We identified 57 reports describing 40 studies published between 1940 and 2025: 30 non-randomized controlled trials, 4 randomized controlled trials (RCTs), 4 case series, 1 cohort study, and 1 cross-sectional study. Non-randomized studies indicated GUV reduces infections with high transmissibility through air (measles and chickenpox), although results were mixed for undifferentiated respiratory illnesses and absenteeism. Two RCTs were inconclusive or showed only modest effects. Safety monitoring in 16 studies identified no increased eye or skin irritation from properly installed GUV. All studies had at least one threat to validity; 89% were non-randomized, and 83% lacked statistical power calculations. LIMITATIONS: Heterogeneous study designs, interventions, and outcomes precluded meta-analysis. CONCLUSIONS: Several older clinical studies indicated that GUV reduces infections with high transmissibility through air, but its broader effectiveness against respiratory infection remains uncertain. Inconclusive results may reflect methodological and epidemiological limitations rather than true ineffectiveness. Adequately powered RCTs with robust clinical endpoints are needed. REGISTRATION: https://osf.io/fg6qx.