Lady Macbeth is enjoying renewed popularity in light of the current coronavirus situation. Will these hands neer be clean she asks in the famous sleepwalking scene as she mimics washing her hands. She doesnt exactly exercise the right technique, but of course, the action is symbolic. The damned spot she is trying to rid herself of isnt physical, it is guilt.

Today, handwashing has a different kind of guilt associated with it. That guilt descends if we dont sing at least two stanzas of Happy Birthday as we lather with soap, scrub the backs and palms, twist a thumb as we grip it with the other hand or ensure that our nails have received enough attention. Although soap was well-known by 1606 when Shakespeare wrote his classic play, it was not commonly used. Sanitation was not a component of life. Any knowledge that invisible microbes could transmit disease would not emerge until the 19th century. However, even before Louis Pasteur laid the foundations for the germ theory of disease in the 1860s, a Hungarian physician hit upon the importance of washing hands to prevent disease transmission.

As a young doctor, Ignaz Semmelweiss was keenly aware of childbed fever. It was not unusual for a mother to die within a week of giving birth, but he did note that more women were dying after giving birth if they were attended by doctors than by nurses. Semmelweiss became obsessed with this conundrum. He performed numerous autopsies on the dead women in a search of some causative agent, but found none. Then in 1847 came a tragic breakthrough. One of his colleagues cut himself during an autopsy and soon died of symptoms that were remarkably similar to childbed fever. Semmelweiss surmised that some sort of cadaver particles must have gotten into his friends bloodstream and killed him. And perhaps these same cadaver particles were also killing the women! Now the difference between the two obstetrics wards became clear. The doctors who assisted in the births in the infamous death ward, and who performed internal exams on the women before and after birth, often came directly from the autopsy room where they were trying to solve the horrific problem of childbed fever. Could they be infecting their patients with some sort of cadaver particles? This now seemed possible. After all, doctors hands constantly smelled of cadavers.

The conclusion now seemed obvious. Semmelweiss urged all doctors and students to thoroughly wash their hands after performing autopsies. But even with thorough washing, a faint smell of the autopsy room persisted so he decreed that the hands should be rinsed in a hypochlorite solution. Hypochlorite bleach at the time was already known to eliminate smells, although why it did so was not understood.

The results of the hand washing bordered on the miraculous. Within a year, the death rate fell from a high of 30 per cent to 3 per cent. The notorious death ward was no more. Semmelweiss was elated by this result, but he was also troubled by it. He realized that he himself had probably been responsible for many deaths as he rushed back and forth between the obstetrics ward and the autopsy room. His feelings of guilt coupled with his conviction that he had made a major discovery converted Semmelweiss into a hand wash promoting zealot. Still, it took decades before the importance of handwashing took hold in the medical community.

Today, with our extensive knowledge of disease transmission by microbes it is clear why handwashing works. Bacteria and viruses are either inactivated or rinsed away. Soap molecules have one end that is soluble in water and another that dissolves in fatty substances, or lipids. Most dirt is of an oily or greasy nature and attracts the fat-soluble end, leaving the other end to be anchored in water. Rinsing then pulls the oily dirt off any surface to which it is attached. In the case of COVID-19, soap can actually destroy the virus responsible for the disease. Coronaviruses are composed of a core of nucleic acids, either RNA or DNA, surrounded by a protective coating made of proteins and fats. The fat-soluble end of the soap molecule embeds itself in the lipid layer and the virus is then literally pulled apart since the rinsing water is tugging the other end. The reason for the 20-30 second time period is to ensure that the soap makes contact with whatever microbes may be present.

Washing with soap and water is more effective than using an alcohol-based hand sanitizer. Alcohol can dissolve fats, so it is capable of stripping away the lipid layer of a virus and thereby inactivate it, but the problem is that unlike washing with soap it doesnt remove dirt and may not get at viruses that are stuck in the dirt. Of course, when soap and water are not available, hand sanitizers can step in as long as they contain at least 60 per cent alcohol.

Being urged to stay home because of this virus, why not make use of the opportunity find a version of Macbeth to watch? I dont think eye of newt, toe of frog, wool of bat or tongue of dog are the solution to COVID-19, although equally nonsensical regimens are being peddled by the charlatans who emerge out of the woodwork whenever a crisis such as this presents.

joe.schwarcz@mcgill.ca

Joe Schwarcz is director of McGill Universitys Office for Science & Society (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.

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The Right Chemistry: In hand washing, role of soap is key - Montreal Gazette