So it turns out that hand washing with soap is the best way to kill Covid-19. And alcohol, the active ingredient in most hand sanitisers, is almost as good. I was interested to read the nitty gritty on this by Palli Thordarson (1), an expert in supramolecular chemistry.
Understanding the virus
To understand how Covid-19 is destroyed, it’s helpful to visualise the structure of this virus. It consists of a central core of RNA, similar to DNA, that carries the virus’s genetic code. Outside are a few different types of proteins that give the virus its structure and also help the virus invade our cells. Encapsulating these is a lipid layer, a fatty membrane that protects the virus and also helps it attach to surfaces and invade our cells.
Why is soap so effective at killing Covid-19?
The coronavirus is quite ‘sticky’. Washing our hands with plain water is generally not sufficient to loosen the virus from the skin. Soap is made in a chemical reaction (called saponification) between fats and an alkaline sodium salt. Each soap molecule has a long hydrocarbon chain that is oil soluble, and a negatively charged end that is water-soluble.
When we wash our hands with soap, the oil-soluble end of the soap molecule competes with the lipids on the virus membrane, weakening the bonds that hold the virus together. The soap also competes with the bonds that hold the RNA and proteins within the virus, effectively breaking the virus apart. The water we wash our hands with binds the water-soluble end of the soap molecule, and the virus is dissolved and washed away.
However, at a microscopic level, our skin is rough, and it’s easy for a virus to evade soap with a cursory hand wash. That’s why we have to do a lot of scrubbing and soaking - at least 20 seconds with soap and water - to reach every little crevice in our skin that a virus could be hiding.
What about hand sanitiser?
Hand sanitisers containing alcohol can also disrupt the virus’s lipid membrane when present at high concentrations - at least 60% according to a range of sources. Most say that soap is more effective than alcohol at breaking up the virus. However, when soap is not available, an anti-viral hand sanitiser should be used, and rubbed over the hands for at least 20 seconds for best effect.
How to wash your hands properly
According to a World Health Organisation coronavirus hand hygiene guide, washing your hands properly takes 40-60 seconds. It includes lathering your fingertips and nail beds, the palms and between the fingers. Here is their hand-washing guide (taken from reference 3). Note that when you’ve finished washing you should turn off the tap with your elbow or a hand towel, and you should avoid touching the door handle with your freshly washed hands. And drying is almost as important - take at least as much time to dry thumbs, fingers, front and backs of hands.
Taking it seriously
According to an article by Tomas Pueyo published in Medium (4), taking strong and drastic steps early to prevent the spread of the infection will mean a much lower death rate. High death rates occur when the health system is overwhelmed - hospitals simply don’t have enough beds, equipment and health workers to cope with too many extremely ill people at once. Early strong action to slow down the spread of the virus will reduce the strain on our health sector, and result in far less disruption to our economy and society.
So let’s do our best to keep everyone safe. Wash your hands, maintain social distance, don’t go out if you’re sick, don’t panic, and be the first to help others when you can.