Plain water is better than hand sanitiser for influenza A

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Simple handwashing, even without soap, is more effective than using many hand disinfectants for killing influenza A virus (IAV) in typical clinical situations, new data show.

The researchers say the key factor that determines the effectiveness of ethanol-based disinfectants (EBDs) is whether there is wet mucous surrounding the virus. Wet mucous prevents the disinfectant from reaching the virus, which means the virus remained active after 120 seconds of EBD exposure.

By contrast, washing hands under plain water for 30 seconds inactivated the virus, regardless of whether it was initially surrounded by wet or dry mucous.

"The physical properties of mucous protect the virus from inactivation," said lead researcher Dr. Ryohei Hirose, physician and molecular gastroenterologist at Kyoto Prefectural University of Medicine in Japan. "Until the mucous has completely dried, infectious IAV can remain on the hands and fingers, even after appropriate antiseptic hand rubbing."

Hirose and colleagues published their findings online in mSphere.

For the study, they first looked at the physical properties of mucous and found that ethanol travels more slowly through the thick, sticky substance than it does through saline, which has similar properties as plain water.

Next, the researchers attempted to simulate clinical situations in which healthcare professionals might transmit the virus: they collected sputum for IAV-infected patients and applied it to human fingers. After being exposed to an EBD for 2 minutes, the IAV was still active in the mucous on participants' fingertips. The virus was deactivated by 4 minutes.

If, however, the researchers allowed the mucous to fully dry on participants' hands before they used EBD, the hand sanitiser quickly inactivated the virus.

The Centers for Disease Control and Prevention and the World Health Organization recommend using disinfectants such as EBDs for 15 to 30 seconds. "However, our results suggest that this disinfection time is insufficient for the disinfection of infectious mucous of IAV-infected patients adhered to the fingers/hands and that current contact infection prevention and [antiseptic hand rubbing] regimens using EBDs are not sufficient to prevent IAV outbreaks," the researchers write.

The findings challenge those of previous studies, most of which have tested EBDs on dry mucous. Given their results, the authors recommend actually washing hands and not simply rubbing them with hand disinfectant.