UV Light Cuts Spread Of TB

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Ultraviolet lights could reduce the spread of tuberculosis in hospital wards and waiting rooms by 70 per cent, according to a new study involving researchers from the University of Leeds.

The study, published in PLoS Medicine today, explores the transmission of tuberculosis (TB) from infected patients, and suggests that installing simple ultraviolet C (UVC) lights in hospitals could help reduce the transmission of even drug-resistant strains.

Every year, more than nine million people are infected with tuberculosis and approximately two 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.

When a tuberculosis patient coughs, bacteria are sprayed into the air in tiny droplets, floating around the room and infecting other patients, visitors and healthcare staff. These bacteria can be killed by hanging a shielded UVC light from the ceiling and ensuring an effective system to move and mix the air, say the researcher team, which includes the University of Leeds, Imperial College London, Hospital Nacional Dos de Mayo, Lima, Peru, and other international institutions.

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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.

The impact of UV lights is greatest when combined with careful management of the air flow on the wards, as Dr Cath Noakes from Leeds’ Faculty of Engineering explains: “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. 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.”

A specialist in hospital ventilation and air flow management, Dr Noakes is already building on the results of the Peruvian trial in new research aimed at developing practical guidelines for the installation of UV infection control systems. By creating computational models of UV lights in realistic environments such as hospitals and clinics, Dr Noakes will determine in which environments the UV is most beneficial and design systems to interact effectively with the air flow in the building.

“The trial showed that UV can work,” says Dr Noakes. “For hospitals and other institutions to be able to use it with minimum cost but maximum impact, we now need to know the details – where the UV lights need to be placed to work most effectively and safely and what changes to ventilation systems may be required.”

Lead researcher Dr Rod Escombe, from the Wellcome Trust Centre for Clinical Tropical Medicine at Imperial College London says: “Thankfully, the rate of tuberculosis infection in countries like the UK is relatively low and people who are infected can be treated using antibiotics, which are readily available here. People are more likely to die from the disease in developing countries like Peru, because there are limited resources for isolating patients, diagnosing them quickly and starting effective treatment. Also, the prevalence of drug-resistant TB is much higher in the developing world. Preventing infection is much easier and cheaper than treating a patient with tuberculosis.”

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.

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