New York

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.

Influenza virus spreads from person to person mainly through fine liquid droplets, or aerosols, that become airborne when people with flu cough, sneeze, or talk.

The study, published in the journal Scientific Reports, was designed to test if far-UVC light could efficiently kill aerosolized influenza virus in the air, in a setting

similar to a public space.

In the study, aerosolized H1N1 virus—a common strain of flu virus—was released into a test chamber and exposed to very low doses of 222 nanometres far-

UVC light.

A control group of aerosolised 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.