Hand-washing six to 10 times a day is linked to a lower risk of seasonal coronavirus, supporting public health guidance around measures for the COVID-19 outbreak, research suggests.


Regular hand-washing can reduce personal risk of getting an infection, a study, which has not been peer-reviewed, indicates. Moderate-frequency hand-washing was associated with a 36 per cent reduction in the risk of coronavirus infection compared to those who washed their hands zero to five times per day.

There were no additional benefits to hand-washing more than 10 times a day, the researchers say.

The paper is currently a ‘pre-print’, meaning it hasn’t been vetted by a group of scientists who will assess if the science – the method, the analysis and the inferences drawn from the data – stands up.

The peer review process is designed to weed out errors, misinterpretation or flawed research methods. But in order to speed up the distribution of research (as the peer review process takes time) scientists do post papers to pre-print archives first.

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Dr Sarah Beale from University College London’s (UCL) Institute of Health Informatics, and first author on the study, said: “Given that COVID-19 appears to demonstrate similar transmission mechanisms to seasonal coronaviruses, these findings support clear public health messaging around the protective effects of hand-washing during the pandemic.

“It’s important to highlight that frequency of hand-washing is only one aspect of hand hygiene. We also know that both longer duration of hand-washing and the context of hand-washing e.g. upon returning home or before eating – have been associated with lower overall risk of influenza or influenza-like-illness.

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“Good hand hygiene should be practised at all times regardless of whether you show symptoms or not. This will help protect yourself and prevent unwittingly spreading the virus to others around you.”

Something as simple as washing our hands regularly can help us to keep the infection rate low and reduce transmissions
Ellen Fragaszy

The research, published in Wellcome Open Research draws on data from three successive winter cohorts (2006 to 2009) of the England-wide Flu Watch study.

For the study, 1,633 participants provided baseline estimates of hand hygiene behaviour and coronavirus infections were identified from nasal swabs. Almost 80 per cent of participants were aged over 16.

At the start of each season, participants were asked to estimate how many times they had washed their hands the previous day. Frequency of daily hand-washing was subsequently categorised as low, zero to five times daily, moderate, six to 10 times daily, or high, more than 10 times daily.

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Ellen Fragaszy, UCL Institute of Health Informatics and the London School of Hygiene and Tropical Medicine, said: “Something as simple as washing our hands regularly can help us to keep the infection rate low and reduce transmissions.”

The authors write: “This is the first empirical evidence that regular hand-washing can reduce personal risk of acquiring seasonal coronavirus infection. These findings support clear public health messaging around the protective effects of hand-washing in the context of the current COVID-19 pandemic.”


The research was funded by The Medical Research Council and Wellcome Trust.

What is the R number, and why is it relevant to coronavirus?

The reproduction number – often called the R value or R number – is a measure of a disease’s ability to spread. It tells us how many people a single infected person will pass on the disease to.

The R number for COVID-19 that’s being quoted in the media and government briefings is what’s known as the ‘effective’ reproduction number. This value can go up and down.

We can reduce R by making it harder for the disease to spread, by implementing measures such as social distancing, closing restaurants and non-essential shops, and encouraging people to stay at home.

Every disease also has what’s called a ‘basic’ reproduction number, R0, which is the fixed value of R if no measures are put in place. For example, measles is highly contagious, with a R0 as high as 18, while COVID-19 has a R0 of around three.

So if COVID-19 was allowed to spread through the population, an infected person would, on average, give the disease to three other people.

But if all these people are practising physical distancing, then the virus can’t spread so easily and the effective R value goes down.

The crucial thing is to keep R below 1. If we can do this, then the number of new cases dwindles and the outbreak will eventually come to a halt.

Conversely, if R rises above 1, then we run the risk of rapidly escalating case numbers that would require stronger measures to keep the virus under control.

Because of this, R is used by governments to assess how we are doing in our efforts to stop the spread of COVID-19, and to adjust our actions, if needed.

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Sara RigbyOnline staff writer, BBC Science Focus

Sara is the online staff writer at BBC Science Focus. She has an MPhys in mathematical physics and loves all things space, dinosaurs and dogs.