How the humble soap is the most effective against coronavirus | The Daily Star
08:07 PM, March 16, 2020 / LAST MODIFIED: 09:01 PM, March 16, 2020

How the humble soap is the most effective against coronavirus

At a time when hand sanitisers are being hoarded in the panic over the coronavirus outbreak, the most effective tool to combat the virus -- the soap -- should not be overlooked.

The everyday necessity, widely available and cheap, has proven to work best on most viruses, including the new COVID-19.

But why does it work so well? Here's the science behind it.

Prof Palli Thordarson of the School of Chemistry at the University of New South Wales in Sydney, recently offered an explanation in an article.


Viruses are self-assembled nanoparticles and their weakest link -- the lipid (fatty) bilayer -- gets dissolved in soapy water, making the virus fall apart and become inactive, Prof Thordarson, also an expert in supramolecular chemistry and the assembly of nanoparticles, said in the article.

Most viruses consist of three key building blocks: RNA (Ribonucleic acid), the viral genetic material similar to DNA (Deoxyribonucleic acid); proteins, and lipids, which self-assemble to form the virus.

Some viruses, including the coronavirus, interact differently on different surfaces -- skin, steel, timber, fabric, paint and porcelain, to name a few.

After a virus invades a cell, its RNA "hijacks" the cellular machinery and forces the cell to make fresh copies of its own RNA and the various proteins that make up the virus structure.

These new RNA and protein molecules then self-assemble with lipids already present in the cell to form new copies of the virus, which eventually overwhelm the cell, causing it to die or explode, releasing the viruses that then spread and infect more cells.


When you cough or sneeze, tiny droplets from the airways that can fly up to 30 feet carry the viruses with them. These end up on surfaces and dry out quickly.

Now, the surface where these land on matters in this case as the virus can remain active on organic surfaces of fibres or wood for hours, even a day.

Our skin, on the other hand, is an ideal surface for the viruses to thrive.

Besides being organic, our skin interacts with the viruses by providing proteins and fatty acids present in the dead cells on the surface.

So,if a person touches a steel surface with a virus particle on it, it will stick to their skin and, hence, get transferred on to the hands.

But the person is not"infected" until they touch certain parts such as the face, eyes or mouth,through which the virus can enter the body.

Also, if the virus is on one's hands, they can pass it on by shaking hands with someone else, or through other physical contact.

So, unless we wash off the active virus from the hands soon enough, we are at high risk since we are habituated to often touch our faces.

Washing with plain water is not very effective. The virus is sticky and may not budge, Prof Thordarson said.

Soap contains fat-like substances known as amphiphiles, which are somewhat structurally similar to and compete with the lipids in the virus membrane, and mixed with water it effectively dissolves the glue that holds the virus together.

The virus gets detached from the skin surface and falls apart, only to be carried away by the running water as we wash the hand.

Since the skin surface is rough and wrinkly, we need a fair amount of rubbing and soaking (for at least 20 seconds) to ensure the soap reaches every nook and cranny where the active viruses could be hiding.


Alcohol-based disinfectants, hand sanitisers and antibacterial products typically contain ethanol, sometimes with a bit of isopropanol, water and a bit of soap.

Ethanol and other types of alcohol do not only readily form hydrogen bonds with the virus material but, as a solvent, are more lipophilic than water. Hence, alcohol does dissolve the lipid membrane and disrupt other supramolecular interactions in the virus.

However, we need a fairly high concentration of alcohol solution, typically 60%-80% ethanol, to get a rapid dissolution of the virus.

Also, in general, alcohol is not as good as regular soap at this task.

Apart from alcohol and soap contents in disinfectants, or liquids, wipes, gels and creams, the antibacterial agents, such as Triclosan, present in these do not have much effect on the virus structure.

In fact, many antibacterial products are just an expensive version of soap in how they act on the viruses.

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