Efficacy of Hand Sanitizers Against Influenza

Ethanol-based disinfectants (EBDs), commonly known as hand sanitizers, are a good defense against flu viruses, though there is room for improvement with this disinfection method, according to a report published in mSphere.

Investigators from Japan examined the effectiveness of EBDs against seasonal influenza A virus (IAV) in order to determine the actual efficacy of these hand sanitizers against pathogens in mucus. Recent literature on the subject suggests mucosal proteins may decrease the effectiveness of EBDs, the study authors explained. The team had previously established that effectiveness of EBDs against IAV in mucus may depend on physical factors such as viscoelasticity and not chemical factors, such as organic matter.

“From the viewpoint of mass transfer theory, we had predicted that the virus in mucus would be somewhat resistant to alcohol disinfectants,” study co-leader Ryohei Hirose, MD, PhD, a physician and molecular gastroenterologist, explained to Contagion®.

Ryohei Hirose, MD, PhD

“However, we found that the protective effect of mucus is stronger than expected and there may be room for improvement in current hand hygiene guidelines.”

The investigators evaluated IAV inactivation in antiseptic hand rubbing (AHR) with EBDs and antiseptic handwashing (AHW) methods among the mucus that adhered to the hands and fingers of 10 volunteers. While IAV in saline was completely inactivated by AHR using EBD after 30 seconds, IAV in all mucus samples remained active even after AHR for a full 2 minutes. It was not completely inactivated by AHR until 4 minutes of hand rubbing with EBDs, the investigators found. IAV was quickly inactivated by AHR (within 30 seconds) in both dried mucus samples and dried saline samples. IAV was quickly inactivated by AHW within 30 seconds in all conditions, including dried/undried mucus and saline samples.

“The finger pad test conducted in this study is a test that hardly considered hand rubbing,” Hirose further explained. “Hand rubbing is expected to contribute significantly to the increase in the rate of ethanol concentration in infectious mucus due to an increase in convection. Since actual AHR actively rubs hands, the effect of AHR on infectious mucus may be higher than the results of our study. The primary purpose of hand rubbing is to spread liquid disinfectant throughout the hands/fingers. However, hand rubbing can greatly contribute to overcoming situations where the effectiveness of AHR is diminished. We are verifying the scientific significance of the act of hand rubbing in order to propose the best AHR regimen including hand-rubbing methods.”

The study authors noted that current US Centers for Disease Control and Prevention and World Health Organization guidelines suggest the use of disinfectants such as EBDs for between 15 and 30 seconds; however, these findings seem to suggest that this time is insufficient for the disinfection of mucus of IAV. Additionally, these findings indicate that current contact infection prevention and AHR regimens that use EBD are not sufficient to prevent IAV outbreaks.

But the investigators also highlighted that AHW completely inactivated IAV in infectious mucus within 30 seconds, which led them to think AHW regimens are more suitable than AHR regimens for the inactivation of infectious mucus such as IAV.

“Readers should be aware that the effectiveness of liquid disinfectants can be reduced against infectious mucus, and should not overestimate the disinfecting effectiveness,” Hirose concluded. “We want the 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.”