Sep 23, 2019

Washing hands can be more effective than hand sanitiser in preventing spread of flu


A new study has challenged the widely-held belief that rubbing your hands together with ethanol-based sanitiser is an effective defence against the flu.

The research, which was published in mSphere, found ethanol-based hand sanitiser would have to be in contact with the flu virus for nearly four minutes to deactivate it.

The flu virus remains infectious in wet mucous even after being exposed to ethanol-based disinfectant for two minutes, the study found.

Thick mucous protects flu virus

Researchers from Japan’s Kyoto Profectural University of Medicine say the reason the virus survives is the thick consistency of mucous. 

The substance’s thick structure prevents the ethanol from reaching and deactivating the flu virus, the researchers say.

“The physical properties of mucus protect the virus from inactivation,” said physician and molecular gastroenterologist, Dr Ryohei Hirose, who led the study with Takaaki Nakaya, an infectious disease researcher at the same university. 

“Until the mucus has completely dried, infectious flu virus can remain on the hands and fingers, even after appropriate antiseptic hand rubbing”, Mr Hirose said. 

Health care providers should take note, Dr Hirose says.

A splash of hand sanitiser, quickly applied, is not sufficient to stop the spread of flu virus. If the virus is not deactivated, health care providers could be enabling its spread, he said.

Research simulated ways virus could be spread

The researchers initially found that ethanol spreads more slowly through the mucous than it does through saline. Then they analyzed mucous collected collected from people infected with the flu virus and dabbed it on human fingers to simulate situations in which medical staff could transmit the virus. 

After two minutes of exposure to an ethanol-based hand sanitiser, the virus remained active. After four minutes the virus had been deactivated.

The research challenges earlier studies that suggest ethanol-based hand sanitiser is effective against fighting the flu virus, the researchers say. 

Dr Hirose suspects earlier studies have been on dry mucous, ub which ethanol-based hand sanitiser can deactivate the flu virus within 30 seconds. 

Dr Hirose did admit that the “fingertip test” used in his study used may not exactly replicate the effects of hand rubbing, which could be more effective.

Current guidelines under question

Both the Centers for Disease Control and Prevention and the World Health Organization recommend using ethanol-based hand sanitiser for 15-30 seconds to prevent the spread of the flu virus. 

But Dr Hirose says that recommendation is not long enough to prevent the spread of flu.

“We want readers to know that there is room for improvement in current hand hygiene regimen, due to the presence of situations where the disinfection effect is reduced,” Dr Hirose said in an interview with the US health news website, Healthline.

Washing hands with soap more effective than hand sanitiser

The good news is, the study found a more effective way to prevent the spread of flu: simple hand washing.

The study found that washing hands with an antiseptic soap killed the flu virus within 30 seconds, regardless of whether the mucous was wet or dry.

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