Study: Regular Handwashing Reduces Personal Risk of Acquiring Seasonal Coronavirus Infection

In a new study looking at 1,633 participants of the England-wide Flu Watch project, a team of researchers found that moderate-frequency handwashing (6-10 times per day) was associated with a reduced overall risk of seasonal coronavirus infection.

The expanding global outbreak of COVID-19 demands an evidence-based public health response.

Seasonal human coronavirus strains (NL63, OC43, 229E, and HKU1) as well as SARS-CoV-2, a novel coronavirus that causes the COVID-19 disease, appear to be transmitted via droplets, direct and indirect contact with infected secretions and, to an unknown extent by aerosol.

Hand hygiene measures are recommended by health authorities and public health experts worldwide to interrupt these transmission mechanisms by preventing viral transfer via contact with infected people and surfaces.

While hand hygiene recommendations are acceptable in a variety of community settings worldwide and are widely recommended by health authorities, evaluation of their effects on the risk of illness in the general population is limited.

“It’s important to highlight that frequency of handwashing is only one aspect of hand hygiene,” said first author Sarah Beale, a researcher in the Public Health Data Science Research Group of the Institute of Health Informatics at University College London (UCL) and the UCL Institute of Epidemiology and Health Care.

“We also know that both longer duration of handwashing and the context of handwashing e.g. upon returning home or before eating — have been associated with lower overall risk of influenza or influenza-like-illness.”

“Good hand hygiene should be practiced 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.”

For the study, Beale and colleagues used data from three successive winter cohorts (2006 to 2009) of the Flu Watch study, a national household-level prospective cohort study investigating transmission, burden and risk factors associated with influenza and other acute respiratory infections across England.

The majority of participants (almost 80%) were adults over sixteen years of age. They provided baseline estimates of hand hygiene behavior. Coronavirus infections were identified from nasal swabs using RT-PCR.

To assess overall handwashing frequency, participants were asked at baseline of each season to ‘Estimate how many times you washed your hands yesterday.’

Frequency of daily handwashing was subsequently categorized as low (≤5 times daily), moderate (6–10 times daily), or high (>10 times daily) guided by literature around influenza-like illness in Western community settings.

The outcome of interest was whether participants contracted any PCR-confirmed coronavirus infection in a season.

Detected coronavirus strains (NL63, OC43, and 229E) were combined into a binary outcome (yes/no coronavirus) as the effect of hand hygiene is believed to be consistent across these strains.

Moderate-frequency handwashing was associated with significantly reduced overall risk of contracting coronavirus (36% reduction in the risk of infection compared to those who washed their hands 0-5 times per day).

For higher intensity handwashing there was no significant dose-response effect.

“Something as simple as washing our hands regularly can help us to keep the infection rate low and reduce transmissions,” said senior author Ellen Fragaszy, a researcher in the Public Health Data Science Research Group at the UCL Institute of Health Informatics and the Department of Infectious Disease Epidemiology at London School of Hygiene & Tropical Medicine.

“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 handwashing during the pandemic,” Beale added.

The findings appear in the journal Wellcome Open Research.