10/19/2016 04:46 pm ET Updated Oct 20, 2017

Spreading Viruses in the Bath

By Drs. David Niesel and Norbert Herzog

You never know when you walk into a public restroom what you will be using to dry your hands. The options usually are standard or high speed air dryers or paper towels. The battle about which method is more hygienic has heated up again with a recent study showing that high speed dryers spread a virus 60 times more than standard air dryers and 1,300 times more than paper towels.

Anyone who has been to the doctor or been in a hospital has seen the ubiquitous hand sanitizer dispensers at strategic locations. Care givers and patients are highly encouraged to practice good hand hygiene at all times. The other method of hand hygiene is, of course,hand washing using soap and water. The method and completeness of hand drying is also important since incomplete drying is more likely to spread the remaining microbes.

Unfortunately, many people do not adequately wash their hands and are likely to still have microbes on them when they go to dry them. This becomes an issue when drying their hands launches the microbes into the air, which could transmit disease-causing microbes to others. Bacteria are spread further and more often by the high speed dryers than standard dryers and paper towels spread them even less. That is not surprising considering these high speed dryers produce air flows that exceed 400 mph. But what about viruses? Viruses can persist on hands for varying lengths of time. Influenza virus can survive for only 10-15 minutes, herpesviruses for up to 2 hours, the rhinovirus responsible for the common cold can survive a week while hepatitis A virus can survive for up to 2 months.

To test this, researchers applied a harmless virus, MS2, onto their wet gloved hands. The bacteriophage MS2 is a virus that only infects a bacterium called E. coli, a resident in healthy human intestinal tracts that is easy to quantify. Participants then simulated the process of hand washing followed by shaking their hands 3 times and then dried them using either paper towels, standard air dryer or high speed dryer. Petri plates with E. coli were affixed to a vertical board with the outlines of male, female and a child. If the virus hit the plates, the bacteria in the area die leaving a clear zone called a plaque to put a figure on viral spread. The target boards were placed at various distances from the drying device.

The jet air dryer spread the virus over 60 times more than the standard air dryer and over 1300 times more than paper towels. The height at which the maximum numbers of viruses were spread corresponded to the height of a child's head. Viruses spread to distances under 10 feet. These results are perhaps not all that surprising considering the differences in the paper towels absorbing the liquid and the air dryers spreading virus depending on the speed and volume of the air flow. The implications for the spread of viruses in restrooms are clear. Unless people effectively wash their hands, using the air dryer-especially the high speed ones-expose others in the facility to the viruses they carry.

Medical Discovery News is hosted by professors Norbert Herzog at Quinnipiac University, and David Niesel of the University of Texas Medical Branch. Learn more at