UV light kills tuberculosis bacteria by damaging their DNA

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Using ultraviolet (UV) lights in hospital wards and waiting rooms could cut the spread of tuberculosis (TB) in hospitals by 70 per cent, scientists have found.

Researchers hung UV lights — shielded to protect patients — from the ceiling of a hospital ward in Lima, Peru, where 69 patients co-infected with HIV and TB were being treated.

For 18 months one group of guinea pigs received air from the ward on days when the UV lights were switched on and the other group received air from the ward when they were switched off.

When tested, 35 per cent of the control animals had been infected. This was reduced to ten per cent by UV lights. Just four per cent of the animals in the UV group actually developed the disease — compared to nine per cent of the control animals.

UV light kills tuberculosis bacteria — including drug resistant strains — by damaging their DNA. When patients cough they release the bacteria into the air and TB is often passed between hospital patients in crowded wards.

A fan was used to create a constant flow of treated air down to patient level and potentially infected air up towards the lights.

There is no need to replicate the study in humans, according to doctors Roderick Escombe from Imperial College, who led the research, and Eduardo Ticona, principal researcher from Hospital Nacional Dos de Mayo, the Lima hospital where the research was carried out.

"Because the guinea pigs breathed air directly coming from the ward, we can say that the 70 per cent reduction in guinea pig TB reflects a 70 per cent reduction in TB transmission risk in the ward," Escombe told SciDev.Net.

For Ticona, the main barrier to disseminating this technology is cost. Members of the team are working on low-cost lights, and the researchers hope that these units will cost around US$100 as compared with US$650–700 for imported lights. 

UV lamp fixtures are already made in South Africa and could easily be designed and mass-produced in low-income countries, Escombe adds. "Furthermore, once installed, the lights just need to be switched on."

But Raúl Salazar, head of the Internal Medicine-Infectology-HIV Service of the Guillermo AlmenaraGeneralHospital in Lima, is cautious. He told SciDev.Net that while the study is useful, more research is required into the long-term effects of exposure to UV lights.

Link to full article in PLoS Medicine