Soap and Water Hand Washing Superior to Alcohol-Based Rubs in Reducing Presence of Influenza A

February 16, 2009

February 13, 2009 — Soap and water hand washing and alcohol-based rubs are effective reducing the presence of influenza A virus on human hands, according to the results of a study published in the February 1 issue of Clinical Infectious Diseases. Hand hygiene may play an important role in reducing the transmission of pandemic and avian influenza among healthcare workers, patients, and caregivers.

"Although person-to-person transmission of influenza virus is due primarily to aerosol spread, transmission on the hands of patients and their caregivers is also potentially important," write M. Lindsay Grayson, MBBS, MD, MSC, FRACP, FAFPHM, from the Infectious Diseases Department, Austin Health, the Department of Epidemiology and Preventive Medicine, Monash University, and the Department of Medicine, University of Melbourne, Australia, and colleagues. "Appropriate hand-hygiene practices should reduce transmission risk, but there are few in vivo data to confirm the antiviral efficacy of currently available HH protocols. Furthermore, the long-term viability of influenza virus on unwashed human hands remains unclear."

The researchers evaluated the use of 5 hand hygiene protocols on 20 healthcare workers who had previously undergone vaccination with the influenza virus. The hand hygiene protocols included 3 alcohol-based hand rubs (61.5% ethanol gel, 70% ethanol plus 0.5% chlorhexidine solution, and 70% isopropanol plus 0.5% chlorhexidine solution), soap and water hand washing, as well as a control protocol which contained no hand hygiene technique.

In an attempt to mimic a worse-case clinical scenario, a high contaminating concentration of live influenza A virus (H1N1 strain) was poured into the right palm of study participants and then allowed to air dry for 2 minutes. The concentration of H1N1 was evaluated by viral culture and real-time reverse-transcriptase polymerase chain reaction (PCR) both before and after the use of the hand hygiene protocols. In addition, a subset of the participants (n = 8) were assessed for the natural viability of the virus over time in their hands. Among these participants, hand hygiene techniques were not used and their hands remained contaminated for 60 minutes before being evaluated for the concentration of H1N1.

Interestingly, the results of the study revealed that the virus was undetectable in 30% of the participants following the 2-minute air drying period. Nevertheless, no further reductions in the viral concentration occurred following the additional 60-minute waiting period among the subset of participants used to assess the natural viability of H1N1. In the article, Dr. Grayson and colleagues explain that “human hands may be a naturally hostile environment for H1N1 and that the initial act of drying and possibly the presence of natural skin oils on the hands may also have an antiviral effect.”

Among those participants with detectable H1N1 after the 2-minute drying period, the 3 alcohol-based hand rubs as well as soap and water hand washing were effective in reducing the viral concentration on participants' hands. However, soap and water hand washing was shown to be statistically superior (P < .001) to the alcohol-based hand rubs. The actual difference, though, in viral concentration on the healthcare worker’s hands with soap and water hand washing vs the alcohol-based hand rubs was only 1-100 copies/µL.

"We believe that our findings have potentially important public health implications, because simple hand washing with unmedicated soap and water appears to be highly effective in removing influenza virus from hands and is, therefore, likely to be effective in preventing transmission of influenza, as long as [hand hygiene] is undertaken appropriately," the authors conclude. "For busy HCWs for whom the number of [hand hygiene] opportunities is likely to be very high, the use of [alcohol-based hand rubs] would seem to be a very suitable alternative."

Clin Infect Dis. 2009;48:285–291.

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