see issue 59 of HIV This Week

Using the guinea pig air sampling model of the 1950s to advance further their DNA fingerprinting study which showed that 8.5% of 118 TB patients were responsible for 98.9% of the guinea pig infections (see issue 59 of HIV This Week), these authors turned their attention to preventing TB transmission. This is the first controlled evaluation assessing the effects on airborne TB transmission in a clinical setting of upper-room ultraviolet (UV) light that kills M. tuberculosis and negative ionization which gives airborne particles a charge that makes them stick to surfaces. Despite the high humidity of Lima (70 to 90%) which would affect UV germicidal efficacy, upper-room UV light had a marked effect reducing both TB infection (70%) and disease (54%). Although these are guinea pig studies, the evidence for this environmental control measure is strong. Upper-room UV lighting is relatively low cost compared to mechanical ventilation and should be expertly installed now in all waiting rooms, out-patient and emergency departments, and antiretroviral treatment facilities where undiagnosed and untreated TB patients are likely to be found. Designing simple UV fixtures for low-resource settings will facilitate scale-up further.