Handwashing with soap and water reduces the numbers of germs in two primary ways:
Fat and water do not mix. Try to wash oil or grease off your hands with just water, and you get the picture. So, the mechanical removal is not our most effective option, and is likely only to work on microorganisms loosely adherent (hanging on) to the hands.
We want destruction, and old-fashioned soap is the solution.
Handwashing with soap (it does not have to be anti-bacterial) is able to destroy germs, especially viruses, and is the most effective way of reducing their spread.
How does soap destroy viruses?
Soap is made when a fat/oil is mixed with something alkaline, such as sodium hydroxide (for hard soaps) or potassium hydroxide (for soft, liquid soaps). If we could zoom in on the soap molecule, we would see it has a head and tail. The head is ‘hydrophilic,’ meaning it is attracted to water, while the tail is ‘hydrophobic,’ meaning it is attracted to oil, fat or grease, but repelled by water.
So, when soap is added to the oil and water, for example, the soap fat-loving tails pulls the fat from the oil into the water, helping it dissolve. Thanks to the soap, the oil becomes soluble in the water.
This is the key action used in destroying viruses off your hands.
Here is a common image of novel coronavirus, which can lead to severe acute respiratory syndrome (or SARS-CoV-2), specificually called the 'coronavirus disease 2019' or COVID-19. It has these little protein spikes, the RNA inside, and a fatty (or lipid) membrane – which is the Achilles heel of the virus. The fat-loving tails of the soap compete with the fat in the virus’ membrane, ripping the membrane apart, dissolving it, so that the virus contents can be washed down the drain of the sink.