UV light cuts spread of TB

Published: 31-Mar-2009

Ultraviolet lights could reduce the spread of tuberculosis (TB) in hospital wards and waiting rooms by 70%, according to a new study, published in PLoS Medicine.1


The study, which explored the transmission of TB from infected patients to guinea pigs, suggests that installing simple ultraviolet C (UVC) lights in hospitals could help reduce the transmission of TB, including drug-resistant strains.

Every year, more than 9 million people are infected with tuberculosis and nearly 2 million people die from the disease, according to the World Health Organisation. Infection rates are particularly high in places where vulnerable people are crowded together, such as hospitals, homeless shelters and prisons.

Spread by droplet infection, the bacteria can be killed by hanging a shielded UVC light from the ceiling with a fan to mix the air, say the researchers, from Imperial College London, the University of Leeds, Hospital Nacional Dos de Mayo, Lima, Perú and other international institutions.

UVC light kills tuberculosis bacteria, including drug-resistant strains, by damaging their DNA so they cannot infect people, grow or divide. It is already used at high intensity to disinfect empty ambulances and operating theatres.

Plans are already underway to install upper room UV lights in the chest clinic at St Mary's Hospital, London, which will be the first hospital to have them in the UK. Introducing UVC lights could be a relatively low-cost measure, say the researchers. Currently, a typical UVC ceiling light costs around US$350 (€263)and replacement bulbs cost from US$25 (€19). The researchers are now working to develop more affordable US$100 (€75) units.

The impact of UV lights is greatest when combined with careful management of the air flow on the wards. "The lights must be set high enough to ensure patients and health workers are not overexposed, but if the lights only treat air at that level, there will be little benefit,” explained Dr Cath Noakes from the University of Leeds' Faculty of Engineering. “To be most effective, ventilation systems need to create a constant flow of treated air down to patient level, and potentially infected air up towards the lights." The research was funded by the Wellcome Trust, Sir Halley Stewart Trust and the Sir Samuel Scott of Yews Trust, Proyecto Vigia (USAID) and the charity Innovation for Health and Development (IFHAD).

www.imperial.ac.uk

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