In In the past few weeks we have been reminded, like a prayer wheel, to wash our hands thoroughly and frequently, to protect against infection with the SARS-CoV-2 coronavirus. Leading global health authorities, including the Robert Koch Institute in Germany, backed by a wealth of scientific evidence, make the case that hand washing with soap is one of the most effective means of reducing the spread of SARS-Cov-2. But why is this so important right now and why is washing hands with soap even more effective in everyday life than rubbing in with a conventional hand disinfectant?
The SARS-CoV-2 coronavirus is responsible for the disease COVID-19, and belongs to the species of Severe Acute Respiratory Syndrome (SARS)-associated coronaviruses. These are pure RNA viruses, consisting of a single-stranded RNA (ssRNA) genome that encodes four major structural protein genes: The nucleocapsid (N) protein, the spike (S) protein, the membrane (M) protein, and the envelope (E) protein. The S, M and E proteins penetrate the lipid bilayer that forms the virus envelope, or “outer skin” of the coronavirus. This lipid membrane consists of a phospholipid double layer. The virus envelope makes the virus more adaptable to the host's immune system and therefore more dangerous.
In the absence of a vaccine, an important target in the fight against SARS-Cov-2 remains the lipid bilayer of the virus envelope, which soap has the ability to disrupt effectively. The surfactants contained in soap (and also detergents) are amphiphilic, i.e. they consist of a hydrophilic (Greek: "water-loving") and a hydrophobic (Greek: "water-avoiding") part, also called lipophilic ("fat-loving"). The surfactants form micelles in aqueous solution: These are spherically arranged molecules in which the hydrophilic portion is oriented towards the water, but the lipophilic portion is directed towards the inside. This lipophilic part of the micelles absorbs fat components. In the case of enveloped viruses, the micelles encapsulate and dissolve the lipid-containing virus envelope. The outer, water-soluble portion of the micelles assists removal of virus remnants when rinsed thoroughly under tap water
Disruption of the virus envelope exposes the RNA, and renders the virus non-infectious. The RNA is rapidly cleaved by ribonucleaeses, which are abundant on human skin.
To clean the skin thoroughly, care should be taken to foam the soap and to maintain a hand washing time of at least 20 seconds and to thoroughly rinse off virus remnants.
The alcohol contained in hand disinfectants also destroys the lipid layer. However, the alcohol content should be at least 60% and the exposure time of the disinfectant should not be less than 30 seconds. Sufficient disinfectant must be put in the palm of the hand, the hollow hand should be completely filled with it and fingernails and skin folds should be well coated with the disinfectant. Because the disinfectant is allowed to air-dry on the skin, instead of being rinsed off afterwards, it is essential to ensure correct use and exposure time. Washing hands with soap and water seems to be the easier and more practical option in everyday life.
SARS-Cov-2 coronavirus and soap: Why washing your hands really makes sense