Abstract:
RATIONALE : Transmission is driving the global tuberculosis epidemic,
especially in congregate settings. Worldwide, natural ventilation is
the most common means of air disinfection, but it is inherently
unreliable and of limited use in cold climates. Upper room germicidal
ultraviolet (UV) air disinfection with air mixing has been shown to be
highly effective, but improved evidence-based dosing guidelines are
needed.
OBJECTIVES : To test the efficacy of upper room germicidal
air disinfection with air mixing to reduce tuberculosis
transmission under real hospital conditions, and to define the
application parameters responsible as a basis for proposed new
dosing guidelines.
METHODS : Over an exposure period of 7 months, 90 guinea pigs
breathed only untreated exhaust ward air, and another 90 guinea pigs
breathed only air from the same six-bed tuberculosis ward on alternate days when upper room germicidal air disinfection was
turned on throughout the ward.
MEASUREMENTS AND MAIN RESULTS : The tuberculin skin test
conversion rates (.6 mm) of the two chambers were compared. The
hazard ratio for guinea pigs in the control chamber converting their
skin test to positive was 4.9 (95% confidence interval, 2.8–8.6), with
an efficacy of approximately 80%.
CONCLUSIONS : Upper room germicidal UV air disinfection with air
mixing was highly effective in reducing tuberculosis transmission
under hospital conditions. These data support using either a total
fixture output (rather than electrical or UV lamp wattage) of
15–20 mW/m3 total room volume, or an average whole-room UV
irradiance (fluence rate) of 5–7 mW/cm2, calculated by a lighting
computer-assisted design program modified for UV use.
