Low doses of ultraviolet light can kill airborne flu viruses without harming human tissues, and could be used in hospitals, schools and other public spaces to check the spread of the infection, a study has found.
Scientists have known for decades that broad-spectrum ultraviolet C (UVC) light, which has a wavelength of between 200 to 400 nanometres, is highly effective at killing bacteria and viruses by destroying the molecular bonds that hold their DNA together.
This conventional UV light is routinely used to decontaminate surgical equipment.
"Unfortunately, conventional germicidal UV light is also a human health hazard and can lead to skin cancer and cataracts, which prevents its use in public spaces," said David J Brenner, professor at Columbia University Irving Medical Center (CUIMC) in the US.
Researchers had earlier hypothesised that a narrow spectrum of ultraviolet light called far-UVC could kill microbes without damaging healthy tissue.
"Far-UVC light has a very limited range and cannot penetrate through the outer dead-cell layer of human skin or the tear layer in the eye, so it's not a human health hazard," said Brenner.
"But because viruses and bacteria are much smaller than human cells, far-UVC light can reach their DNA and kill them," he said.
In their earlier studies, researchers demonstrated that far-UVC light was effective at killing MRSA (methicillin- resistant S aureus) bacteria, a common cause of surgical wound infections, but without harming human or mouse skin.
A control group of aerosolized virus was not exposed to the UVC light. The far-UVC light efficiently inactivated the flu viruses, with about the same efficiency as conventional germicidal UV light.
"If our results are confirmed in other settings, it follows that the use of overhead low-level far-UVC light in public locations would be a safe and efficient method for limiting the transmission and spread of airborne-mediated microbial diseases, such as influenza and tuberculosis," said Brenner.
"Far-UVC is likely to be effective against all airborne microbes, even newly emerging strains," he said.