Institutional tuberculosis transmission : controlled trial of upper room ultraviolet air disinfection : a basis for new dosing guidelines

摘要

RATIONALE : Transmission is driving the global tuberculosis epidemic,especially in congregate settings. Worldwide, natural ventilation isthe most common means of air disinfection, but it is inherentlyunreliable and of limited use in cold climates. Upper room germicidalultraviolet (UV) air disinfection with air mixing has been shown to behighly effective, but improved evidence-based dosing guidelines areneeded.OBJECTIVES : To test the efficacy of upper room germicidalair disinfection with air mixing to reduce tuberculosistransmission under real hospital conditions, and to define theapplication parameters responsible as a basis for proposed newdosing guidelines.METHODS : Over an exposure period of 7 months, 90 guinea pigsbreathed only untreated exhaust ward air, and another 90 guinea pigsbreathed only air from the same six-bed tuberculosis ward on alternate days when upper room germicidal air disinfection wasturned on throughout the ward.MEASUREMENTS AND MAIN RESULTS : The tuberculin skin testconversion rates (.6 mm) of the two chambers were compared. Thehazard ratio for guinea pigs in the control chamber converting theirskin test to positive was 4.9 (95% confidence interval, 2.8–8.6), withan efficacy of approximately 80%.CONCLUSIONS : Upper room germicidal UV air disinfection with airmixing was highly effective in reducing tuberculosis transmissionunder hospital conditions. These data support using either a totalfixture output (rather than electrical or UV lamp wattage) of15–20 mW/m3 total room volume, or an average whole-room UVirradiance (fluence rate) of 5–7 mW/cm2, calculated by a lightingcomputer-assisted design program modified for UV use.