Most currently recommended interventions to control airborne infection have never been rigorously tested against human-generated infectious aerosols, in part because of an inability to quantitatively air sample for most airborne pathogens under real life conditions. We plan to study patients with infectious multi-drug resistant tuberculosis (MDR-TB) as a prototype airborne infection in a unique Airborne Infections Research (AIR) facility in South Africa designed to efficiently test the efficacy of infection control interventions through the use of quantitative guinea pig air sampling. Guinea pigs in one of two identical chambers are exposed on alternate days to the exhaust air from three 2-bed rooms and the common area of the AIR patient suite. The infection control intervention is applied in the patient rooms on alternate days. Guinea pig exposure chamber A receive air from the patient rooms only when the intervention is operative, while exposure chamber B receives air from the patient rooms only under control conditions. The difference in the infection rate of guinea pigs in the two chambers, as determined by tuberculin skin testing, is a measure of the efficacy of the intervention. The HYPOTHESES to be tested are that two rapid response interventions (face masks on infectious persons and portable room air cleaning machines), and one pre-planned preventive interventions (upper room UV air disinfection) can effectively reduce the risk of person to person airborne transmission.
SPECIFIC AIMS : (1) To determine if surgical masks on infectious individuals are at least 50% effective in reducing transmission. (2) To determine if commercial portable air disinfection units are at least 75% effective.
We aim to establish a relationship between clean air delivery rate and room air disinfection, independent of the specific device used. We will test both a conventional HEPA filter unit and novel low-maintenance electrostatic air decontamination technology developed for use in outer space. (3) To determine if upper room UVGI is at least 75% effective, and whether room air mixing and low humidity are critical efficacy factors. SIGNIFICANCE: Influenza, SARS, smallpox, and MDR-TB are among the emerging infectious airborne treats to workers. MDR-TB patients and quantitative guinea pig air sampling in the AIR facility provide a unique model for the efficient testing under conditions of controlled infectious source strength (the alternate day strategy), environment (the AIR facility), and host susceptibility (the guinea pigs), of both conventional and novel infection control interventions to protect workers and other building occupants. Test results obtained with MDR-TB may be applicable to other infections that are completely or partially airborne.
