ICAAC: Rhinovirus on Hands Blocked By Solution for Hours

SAN FRANCISCO, Oct. 2 -- One trouble with washing hands is that they won't stay virus-free. But a combination of ethanol and organic acids can transform a pair of hands into a rhinovirus-killing machine for up to four hours.

Standard soap and water or alcohol sanitizers kill the virus at the time of application, but the effect quickly wears off, said Ronald Turner, M.D., of the University of Virginia in Charlottesville.

But the experimental solution he discussed at the Interscience Conference on Antimicrobial Agents and Chemotherapy "provides a persistent barrier."

He reported on a randomized controlled trial comparing 2% malic and 2% citric acid in a standard ethanol hand-sanitizing solution to the ethanol solution alone. The researchers enrolled 197 healthy volunteers who were seronegative for rhinovirus type 39 and randomized them to a control group and two active treatment groups.

The control group and one active group put 1.8 mL of either ethanol or the experimental solution on the thumbs and first two fingers of each hand, and waited two hours without touching anything.

The second active group put 5 mL of the experimental solution into their palms and spread it on both hands. They then waited four hours without using their hands.

At the end of the waiting period, the volunteers' hands were contaminated with rhinovirus type 39.

After allowing the virus solution to dry, the researchers tested the volunteers' left hands to recover any virus that remained alive. With the right hands, the volunteers were instructed to intentionally inoculate their nasal and conjunctival mucosa.

The study found:

• Of the control group, 57 of 61 volunteers (or 93%) were positive for rhinovirus after two hours, while in the two-hour active group, only one of 60 had the virus on the left hand.
• In the four-hour active group, no virus was recovered.
• Nearly half of the control group -- 26 of 61, or 43% -- became infected with the virus, compared to one of the 60 volunteers in the two-hour active group and two of the 60 in the four-hour active group.
• The differences between the active groups and the controls were statistically significant at P<0.0001.

The study shows that in experimental conditions the organic acid solution can kills rhinovirus for up to four hours, Dr. Turner said.

But to mimic real-world conditions, the researchers conducted a smaller substudy, in which volunteers put either three or four milliliters of the solution on their hands and then used their hands normally for pre-defined periods of time before being challenged with a high titer of rhinovirus.

Nine volunteers used 3 mL of the solution and then waited one, two, or three hours before the virus challenge. When their hands were sampled 10 minutes after the challenge, only two of the volunteers had recoverable virus.

Six volunteers used four milliliters of the solution and then went about their business for four hours before the virus challenge. None of them later tested positive, Dr. Turner said.

These "preliminary data suggest that the virucidal activity associated with this hand treatment may persist for up to three hours under conditions of normal use," he said, adding the effect in a completely natural setting "remains to be established."