A “quick splash” of sanitiser on the hands between patients may not be enough to prevent spread of flu, as flu viruses may need to be exposed to ethanol based sanitizsrs for up to four minutes before they are fully deactivated, a study* published in mSphere suggests.
The influenza A virus (IAV) remains infectious in wet mucus from infected patients, even after being exposed to an ethanol-based disinfectant (EBD) for two full minutes, researchers at Kyoto Profectural University of Medicine, in Japan found.
Viruses in wet mucus were able to survive for longer because the thick hydrogel structure of sputum kept the ethanol from reaching and deactivating the IAV.
"The physical properties of mucus protect the virus from inactivation," said physician and molecular gastroenterologist Ryohei Hirose, who led the study. "Until the mucus has completely dried, infectious IAV can remain on the hands and fingers, even after appropriate antiseptic hand rubbing."
The study suggests that a splash of hand sanitiser, quickly applied, isn't sufficient to stop IAV. Health care providers should be particularly cautious: if they don't adequately inactivate the virus between patients, they could enable its spread, Hirose added.
For the study, the researchers first studied the physical properties of mucus and found that ethanol spreads more slowly through the viscous substance than it does through saline. Then, they analysed sputum that had been collected from IAV-infected patients and dabbed on human fingers (to simulate situations in which medical staff could transmit the virus.) After two minutes of exposure to EBD, the IAV virus remained active in the mucus on the fingertips. By four minutes, however, the virus had been deactivated.
Previous studies have suggested that ethanol-based disinfectants, or EBDs, are effective against IAV.
However, Hirose pointed out that most of these studies tested the disinfectants on mucus that had already dried. When he and his colleagues repeated their experiments using fully dried mucus, they found that hand rubbing inactivated the virus within 30 seconds.
For flu prevention, the World Health Organisation recommends hand hygiene practices that include using EBDs for 15-30 seconds. That's not enough rubbing to prevent IAV transmission, said Hirose.
The researchers found that washing hands with an antiseptic soap was much more effective, it deactivated the virus within 30 seconds, regardless of whether the mucus remained wet or had dried.
*Hirose R, Nakaya T, Naito Y, et al. Situations Leading to Reduced Effectiveness of Current Hand Hygiene against Infectious Mucus from Influenza Virus-Infected Patients. mSphere Sep 2019, 4 (5) e00474-19; DOI: 10.1128/mSphere.00474-19