SALLY BLOOMFIELD
The government’s advice on coronavirus asks the public to wash their hands more often. But how could hand-washing protect us from the virus?
Can washing our hands really protect us against coronavirus? Sally Bloomfield, honorary professor at the London School of Hygiene and Tropical Medicine, explains the science of stopping the spread.
WHY ARE WE BEING ADVISED TO WASH OUR HANDS? Coronavirus is a respiratory illness, meaning it is mostly spread through virus-laden droplets from coughs and sneezes. If you don’t catch coughs and sneezes in a tissue and dispose of it, the virus can end up on surfaces. If someone touches that contaminated surface, the virus can transfer onto their hand. If you have the virus on your hands, you can infect yourself by touching your eyes, mouth or nose. You might think that you don’t touch your face very often, but a 2015 study found that people touch their faces an average of 23 times an hour.
While washing your hands is useful in preventing yourself from getting infected, this is not the main reason the government recommends it. “It’s all about stopping the spread,” says Sally Bloomfield, honorary professor at the London School of Hygiene and Tropical Medicine. “When it comes to stopping the spread of the serious infection in this country, the public have a huge role to play.”
DOES SOAP KILL CORONAVIRUS?
Coronavirus is an ‘enveloped virus’. This means it has a protective outer layer known as a ‘lipid bilayer’. Each molecule making up this layer is shaped like a tadpole, with a water-loving (hydrophilic) head and a waterhating (hydrophobic) tail. These molecules arrange themselves into a ‘bilayer’: two layers piled on top of each other into a sheet, with tails pointing inwards and heads pointing outwards. The molecules are pulled closely into each other to protect the hydrophobic tails from the water in your respiratory droplets when you cough or sneeze. The hydrophilic heads are ‘sticky’, meaning the virus is effective at adhering to your hands – perfect for a microbe that’s trying hard to infect you.
Soap molecules also have this tadpole structure, which is what makes it so useful. Because the soap molecules are so similar to the ones making up the outer layer of the virus, the molecules in the lipid bilayer are as strongly attracted to soap molecules as they are to each other. This disrupts the neatly-ordered shell around the virus, dissolving it in the running water and killing the virus.
DOES ANTIBACTERIAL HAND SANITISER KILL VIRUSES?
Yes. Alcohol-based hand sanitiser will kill viruses if soap and water are not available. Alcohol is an antiseptic and can kill enveloped viruses such as coronavirus, but make sure it contains 60 to 95 per cent alcohol. However, if your hands are visibly dirty, you need to use soap and running water to clean the dirt off.
WILL HAND-WASHING STOP ME FROM CATCHING THE VIRUS? It’s impossible to know whether any particular case of coronavirus could have been prevented by better handwashing. While it is possible to contract coronavirus from touching your face with virus-contaminated hands, you can also catch it directly from the coughs or sneezes of an infected person. So, while washing your hands won’t eliminate your risk of infection, it’s a sensible and powerful safety measure. “It’s a little bit, I think, like wearing a car seatbelt, in that it’s unlikely you’ll get infected at the present time, in the same way as you’re unlikely to have a crash when you go out in your car,” says Bloomfield. “You still go out in your car, but you always belt up your seatbelt.”
We do, however, know that hygiene measures – handwashing, self-isolating when ill, disposing of tissues, etc. – do prevent the spread of respiratory diseases. Following the 2003 outbreak of SARS-CoV in Hong Kong, the Department of Health in China wanted to know how effective the government’s efforts at containing the disease were. Since
SARS-CoV (also a type of coronavirus) was a new strain, there was no benchmark for how far it was likely to spread. What they could measure was the incidence of seasonal respiratory illnesses such as the flu. Compared to the average numbers over the previous five years, the incidence of these seasonal illnesses dropped. The difference was particularly clear in the months of April to June, when the public were the most stringent with their hygiene practices.
HOW SHOULD I WASH MY HANDS?
1. Start by wetting your hands with water. It doesn’t matter whether it’s hot or cold: a 2017 study from Rutgers University in the US found that cold water was just as effective as hot at removing E. coli.
2. Next, apply either bar soap or liquid handwash. Although some studies have shown that bacteria can live on the surface of a bar of soap, others have found that sharing a bar does not transmit disease. 3. Thoroughly rub the soap all over your hands, making sure not to miss your thumbs, or between your fingers and your fingertips. This part of the process should take 20 seconds. The NHS recommends singing Happy Birthday through twice to count out 20 seconds, but you could choose any song with a 20-second chorus, such as Dolly Parton’s Jolene, or Staying Alive by the Bee Gees.
4. Rinse your hands well to remove the soap. Dry them thoroughly, preferably with paper towels.
What you do after you’ve washed your hands is important, too, says Bloomfield. “If you are, say, on an aeroplane or a train, you can wash your hands in the toilet, but you’ve then got to walk back to your seat,” she says. “On an aeroplane, you’re going to be grabbing all the seatbacks that have been grabbed by other people. So, wash your hands, then use a hand sanitiser when you get back to your ‘safe place’, so for example, when you get back to your train seat or plane seat and you’re then not going to move around.”
CAN I WASH MY HANDS TOO MUCH?
All of this extra washing could dry out the skin, so make sure you moisturise your hands too. “If the skin is breaking down or raw, then the soap and alcohol disinfectants do not work as well,” Dr Craig Shapiro, a specialist in paediatric infectious diseases in Delaware, US, told the Washington Post. “Also, when the skin is chapped and broken, it’s uncomfortable, and people can be less likely to wash their hands to prevent transmission of germs and infection.”