Alcohol-based hand sanitizers are thought to provide pretty decent protection from pathogens that spread in saliva and mucus. But is that true? New work reported in mSphere has shown that hand sanitizers aren’t enough to protect us against one type of the flu - the influenza A virus (IAV). It sticks around in the mucus of patients, and stays infectious in wet mucus, even when it’s subjected to an ethanol-based disinfectant (EBD) for two minutes. The thick phlegm protects the virus from the sanitizer’s effects and the study indicated it isn’t deactivated until it's exposed to an EBD for four minutes.
"The physical properties of mucus protect the virus from inactivation," said the study co-leader Ryohei Hirose, Ph.D., MD., a physician and molecular gastroenterologist. "Until the mucus has completely dried, infectious IAV can remain on the hands and fingers, even after appropriate antiseptic hand rubbing."
If a bit of hand sanitizer is quickly rubbed onto the hands, it likely wouldn’t be strong enough to kill IAV that is sitting in a bit of mucus. Clinicians that are treating infected individuals may end up spreading the virus if they’re only using hand sanitizer between patients, noted Hirose.
In this work, the researchers assessed the characteristics of mucus and found, unsurprisingly, that ethanol moves through the thick stuff more slowly than it would through a thin substance like saline. They were able to obtain clinical samples of sputum from patients infected with IAV, which were dabbed onto people’s fingers. The researchers wanted to see whether medical providers might transmit the virus. Again, the IAV stayed active on fingertips even when it was exposed to an EBD for two minutes. It took four minutes of EBD exposure to deactivate the pathogen.
This research challenges other reports that have indicated that EBDs work effectively against IAV. Hirose, who co-led the study with infectious disease researcher Takaaki Nakaya, Ph.D., suggested that such EBD tests demonstrating efficacy are usually conducted with dry mucus. When the researchers repeated their work using mucus that had dried out, the virus was inactivated by EBDs within thirty seconds, confirming their hypothesis.
The video above from the Centers for Disease Control and Prevention discusses effective hand-washing, which should be done for at least fifteen seconds, even in the case of sanitizers. Hirose said that may not be enough to stop IAV, however.