How soap kills coronavirus

During the current coronavirus pandemic, the most effective thing to do in order to keep yourself safe is frequently handwash using soap water. Naturally a question arises that if no drugs can kill this deadly virus then how the soap water can do that job.

Before continuing the discussion, let's get a brief on how the coronavirus spreads. When we cough, or specially sneeze, tiny droplets of water come out of our body and can fly for up to 10 metres. These droplets carry the viruses which then deposit on the surfaces of the objects around. The virus can survive on such surfaces for up to several days.  Then if we touch such surface, our hands get contaminated with the viruses and furthermore when we touch our eyes, nostrils or mouth with our hands, these organs get in touch with the virus.

Human skin is an ideal surface for a virus. As human skin is organic, the proteins and fatty acids in the dead cells on the skin surface link with the virus. This way our body gets infected. To curb the spread of the virus we need to either wash our hands with soap or sanitize our hands using alcohol-based solutions.

According to the opinion of Pall Thordarson, a professor of chemistry at the University of New South Wales, Sydney, published in The Guardian, most viruses consist of three key building blocks: ribonucleic acid (RNA), proteins and lipids. A virus-infected cell makes lots of these building blocks, which then spontaneously self-assemble to form the virus. There are no strong covalent bonds holding these units together, which means strong chemicals are not necessarily needed to split those units apart. When an infected cell dies, all these new viruses escape and go on to infect other cells. Some end up also in the airways of lungs.

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 is not enough to efficiently combat the virus.

Pall says, soapy water is completely different. Soap contains fat-like ingredients known as amphiphiles, some of which are structurally very close 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.

The soap not only loosens the "glue" between the virus and the skin but also the Velcro-like interactions that hold the proteins, lipids and RNA in the virus together. This way soap dissolves the fat membrane and the virus falls apart like a house of cards and dies. "Dies" means the virus becomes inactive.

The alcohol based solutions, best known as the disinfectants, can kill the virus in a similar manner. The most of the solutions contain 60 to 80% ethanol or isopropyl alcohol which is effective in killing the viruses. Between alcohol-based products and soap water, the soap water is more effective for only a little amount of soap water can do the work efficiently and it can kill most of the viruses as well as other germs from the hands. On the other hand, you need to dip viruses into alcohol for a significant amount of time to kill it. Also there is no guarantee that you can rub off all the viruses from every part of your hand using alcohol.

Nevertheless, do use alcohol based sanitizer if it is not possible to wash the hands with soap water as our ultimate goal is to stay germ free.

Md Mazharul Hasan Nur, a freelance blogger and a Mathematics Teacher at Mastermind English Medium School, Dhaka.