UV to C to TB

Researchers have found that altering the light fittings in a hospital could make a dramatic difference to the spread of infectious diseases like TB. Writing in the current edition of the journal PLoS Medicine, scientists in London and Peru explain how they set up a system of UVC (ultraviolet C emitting) lamps in the ceilings of four rooms at an isolation hospital in Lima, Peru, where 69 TB patients were being treated.

Ceiling fans were also positioned to drive air flow from the floor upwards towards the lamps. Over a 535 day period air extracted from the rooms was fed to enclosures housing guinea pigs. Imperial College physician Carlton Evans and his colleagues compared the numbers of animals that developed signs of TB infection when the UV lamps were on compared with a second group of animals exposed to air from the rooms when the lamps were off. The difference was dramatic - 35% of the animals developed TB infection in the lamp-off situation compared with 9.5% of animals exposed during the lamp-on period. The lamps were emitting UVC which is toxic to TB bacteria wafted close to the lamps by the air currents. Because the floor was shielded from the lamps there was no direct risk to staff or patients, none of whom reported any ill-effects. TB is a major world health problem with up to one third of the world poulation said to be infected and at least 9 million new cases and 2 million deaths from the disease occurring annually.

Consequently, say the researchers, this relatively cheap intervention, costing less than US$350 to install, could help to significantly reduce TB transmission in hospitals, clinics or other locations where infectious and susceptible individuals might mix.