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A conference abstract, press released from the European Congress on Clinical Microbiology and Infectious Diseases (ECCMID) conference, reports on paper towels and jet air dryers and removing viruses from hands that hadn’t been washed.
Dr Graham Wheeler, Medical Statistician, UCL, said:
“Previous studies suggest that drying your hands with paper towels after washing may reduce bacterial contamination and transmission risk compared to air dryers. However, there are few studies available to assess which hand-drying approach best reduces viral transmission risk.
“This is an exceptionally small study, with only four people recruited. No firm conclusions on the benefit of using paper towels or jet air dryers can be made from such a small study.
“In this study, all four volunteers were asked not to wash their hands after contamination, to “simulate poor hand-washing practices”. But how many people dry their hands without having washed them first?
“The authors’ conclusions that people should use paper towels after washing their hands can’t be made from this study because that’s not what the investigators tested; they looked at which drying method reduced cross-contamination from unwashed hands.
“A better study would recruit more participants, ask some to wash their hands thoroughly, others to wash them briefly (or without soap), and then dry them using either paper towels or a jet air dryer. You could then measure the benefit of each drying method within and between each hand-washing approach, and also compare the findings to an unhygienic control group who do not wash or dry their hands at all.
“This study has not been peer-reviewed, so all findings should be interpreted with caution.”
Dr Baptiste Leurent, Assistant Professor in Medical Statistics, London School of Hygiene & Tropical Medicine, said:
“This study is an interesting experiment in the current context, but is too small to provide relevant evidence.
“It compared four people who dried their hands using paper towels or hand drier, and looked at the amount of virus on their hands and various surfaces in a real hospital setting. It found a lower amount of virus in those using paper towels.
“This publication is a short conference abstract and it is very difficult to assess the quality of the research, or the value of the results. A clear limitation is that the study was only conducted in four volunteers. It was also not randomised, and it is not clear how comparable the two groups were. Numerous other factors could explain the differences seen. Statistically, it is actually surprising to find “significant” differences with only four volunteers.
“An important point is that in this experiment the volunteers effectively “washed their hands” only using a hair drier or towels, which is clearly different to what happens in practice. It is not clear how these results apply to hand drying after hand-washing, and the relevance for the current recommendations on hand washing. If anything, this study reminds the importance of appropriate hand-washing.”
Prof Kevin McConway, Emeritus Professor of Applied Statistics, The Open University, said:
“It’s pretty difficult to assess the quality of this research, and its implications. All we have is a brief press release, and a brief abstract of the paper that would have been presented at the conference, if it had been able to take place. Some of the details of what was done are far from clear. The research has not yet been peer reviewed by other scientists. And there are several other reasons to be cautious about the results. Overall, I don’t think this piece of research does any more than indicate something that might possibly be worthy of a more comprehensive research study later.
“On the face of it, the results may look fairly clear-cut, but there are many potential reasons for doubt about what the findings mean. Only four volunteers carried out the hand contamination and drying – that’s very few. We aren’t told anything about them. Were they hospital workers who might have learned about the right way to dry one’s hands with paper towels, or members of the general public, or what? In any case it might matter that they knew which hand-drying method they were using – it’s not out of the question that conscious or unconscious biases about paper towels or jet dryers might have affected how they dried their hands. And did each of the four people just do the experiment once, with just one kind of hand drying, or did each of them use both hand drying methods on different occasions – or indeed did they repeat the experiment so that each person’s result was the average of more than one hand-drying occasion? That could very well matter to the interpretation of the statistical results – but we just aren’t told any of these details. There’s really not enough to go on here.”
Dr Simon Clarke, Associate Professor in Cellular Microbiology, University of Reading, said:
“This very small study looks at the effect of paper towels versus hand dryers on unwashed hands – no soap has been used. It’s important to remember that it’s the soap which removes viruses and bacteria from our hands when we wash them, the water is merely there to mix the soap allowing it to be applied to skin and then to wash it off afterwards. These results are neither surprising, nor particularly useful in the battle to control CoViD-19.”
Prof Paul Hunter, Professor in Medicine, UEA, said:
“Whilst the study by Wilcox and colleagues is small, concerns about jet air driers spreading infection are not new. In 2015 Kimmitt Redway from the University of Westminster reported a study showing that such driers were associated with “significantly greater and further dispersal of MS2 bacteriophage from artificially contaminated hands” when compared to warm air driers or paper towels. What both studies have shown is that jet air dryers may lead to greater dispersion of virus onto surrounding surfaces and the persons body compared to paper towels.
“I am not aware of any epidemiological study that has shown that the type of hand drier used has been implicated in the transmission of infection in the real world. Although it would be actually quite difficult to get such evidence even if such transmission was occurring.
“Clearly how much virus remains on peoples’ hands after washing depends to a large extent on how efficiently people are at washing their own hands. If people do not wash their hands properly then other people may be at risk if standing close to someone using such a jet dryer. This study reinforces the need to wash hands properly so as much virus is removed as possible before drying, and the importance of maintaining a two meter distance from other people during the current COVID-19 pandemic even when visiting toilets and washrooms.”
The abstract ‘Dispersal of microbes to hospital surfaces following two hand drying methods: paper towels or a jet air dryer’ by Ines B. Moura et al. has been press released from the European Congress on Clinical Microbiology and Infectious Diseases (ECCMID) conference. There is no paper and this is not peer-reviewed.
Declared interests
None received.