Flu Season Alert: Hand Sanitizer Not Very Effective Against Virus Strain, Study Warns

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Got four minutes? That’s how long researchers say it will take for a person to rub their hands together with sanitizer before Influenza-A is deactivated.


KYOTO, Japan — Flu season is fast approaching, which means millions will be using hand sanitizer more often in an effort to protect themselves from a flu infection. Most people, including medical professionals, believe that flu viruses are quickly neutralized after coming into contact with an ethanol-based sanitizer, but a new study finds that isn’t the case for at least one flu strain.

Researchers from Kyoto Profectural University of Medicine in Japan have discovered that the influenza A virus (IAV) remains active and infectious within infected wet mucus even after being exposed to an ethanol-based sanitizer — for two full minutes. According to their research, it took nearly four minutes of exposure to a sanitizer to completely deactivate the virus.

Needless to say, most people aren’t rubbing their hands together with sanitizer for four minutes.

The influenza A virus is able to survive so stubbornly thanks to the think consistency of sputum, a mixture of mucus and saliva commonly coughed up by flu patients, produced in infected individuals. The thick texture of the sputum impedes the ethanol in the sanitizer from reaching and neutralizing the influenza A virus.

So, imagine someone with the influenza A virus coughs on their hand and then shakes yours a few minutes later. You would have to rub your hands together with sanitizer for four minutes to deactivate the virus if even the slightest trace of wet, infected mucus were to make its way on to your hand.

“The physical properties of mucus protect the virus from inactivation,” says physician and molecular gastroenterologist Dr. Ryohei Hirose in a release by the American Society for Microbiology. “Until the mucus has completely dried, infectious IAV can remain on the hands and fingers, even after appropriate antiseptic hand rubbing.”

According to the study, a small splash of sanitizer quickly rubbed together for a few seconds just isn’t going to cut it against this particular flu virus. The research team say that doctors and other medical professionals should be especially careful; if they don’t properly deactivate the virus between seeing various patients they could quickly spread the flu to multiple people.

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First, the study’s authors analyzed the physical properties of mucus, and just as they expected, they noted that ethanol had a much harder time moving through mucus than it does through saline. Next, sputum collected from IAV patients was dabbed on human fingers and analyzed. The researchers goal during this phase was to try and simulate a situation in which medical personnel transmit the virus as best they could.

After being exposed to an ethanol hand sanitizer for two minutes, the IAV virus was still active within the mucus on the fingertips. After four minutes, the virus was completely deactivated.

This study is especially noteworthy because it challenges previous research that had found ethanol to be effective against IAV. Dr. Hirose, however, believes he knows why his study came to such different conclusions: prior research had analyzed mucus that was already dry, while this study analyzed mucus that was still wet. In fact, when Dr. Hirose and his team repeated their experiment using dry mucus, the virus was completely deactivated by the sanitizer within 30 seconds.

It’s also worth noting that the fingertip test used for this study may not exactly mimic typical hand rubbing motions, which may be a bit more effective at spreading hand sanitizer throughout the hand.

Right now, both the Centers for Disease Control and Prevention and the World Health Organization officially recommend using sanitizer regularly for 15-30 seconds to ensure optimal hand hygiene. Unfortunately, that just isn’t enough rubbing to stop IAV, according to Dr. Hirose.

On the bright side, researchers did identify a hand-cleaning strategy that is even more effective than sanitizers. Washing hands together with antibiotic soap was shown to deactivate the IAV virus within 30 seconds, even when mucus was still wet.

The study is published in the scientific journal mSphere.

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