Alcohol-based disinfectants are effective in the battle against COVID, but one other substance stands taller, according to Pall Thordarson, a chemistry professor at the University of New South Wales in Sydney.

Prof. Thordarson explains in The Guardian why soap works so well. "The virus is a self-assembled nanoparticle in which the weakest link is the lipid (fatty) bilayer. Soap dissolves the fat membrane and the virus falls apart like a house of cards and dies - or rather, we should say it becomes inactive as viruses aren’t really alive.

"Washing the virus off with water alone might work. But water is not good at competing with the strong, glue-like interactions between the skin and the virus. Water isn’t enough.

"Soapy water is totally different. Soap contains fat-like substances known as amphiphiles, some of which are structurally very similar to the lipids in the virus membrane. The soap molecules 'compete' with the lipids in the virus membrane. This is more or less how soap also removes normal dirt from the skin."

Prof. Thordarson says alcohol-based products, which pretty much includes all 'disinfectant' products, contain a high-percentage alcohol solution (typically 60-80 per cent ethanol) and kill viruses in a similar fashion. But soap is better because you only need a fairly small amount of soapy water, which, with rubbing, covers your entire hand easily.

"Wipes or rubbing a gel on the hands does not guarantee that you soak every corner of the skin on your hands effectively enough," he said. However, he added this warning: "So, soap is the best, but do please use alcohol-based sanitiser when soap is not handy or practical."