Public Health Agencies worldwide, including the World Health Organization (WHO) and the Centers for Disease Prevention & Control (CDC), have advocated proper hand hygiene since the very beginning of the coronavirus disease 2019 (COVID-19) pandemic – and continue to do so to the present day.
Scientific evidence proves the benefits of washing hands with soap and water, preventing the dissemination of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. Soap and water induce inactivation of the microbial cell wall and eventual death of most pathogens, including enveloped viruses like the SARS-CoV-2.
Researchers in the United States have reviewed the different components of formulated soaps and their performance as cleansers and pathogen inactivators, the criticality of the time spent hand washing, the relationships between water temperature and pathogen inactivation. They also compared antimicrobial soaps against basic soaps, the effects of alcohol-based sanitizers for hand decontamination and the optimal amount. They also evaluated the limitations and advantages of different methods of drying hands after they have been washed.
This review has been published in a recent issue of the PeerJ journal.
The importance of handwashing in preventing microbial infection
Contaminated hands are the first routes for entry of many pathogens into a host’s system. In healthcare settings, non-compliance with hygiene practices makes healthcare workers vulnerable to the dissemination of nosocomial infections both for themselves and their patients.
Despite basic hand washing and hand hygiene being one of the primary levels of education among children, the larger implications of this simple technique had gained greater currency among the general population only recently during the COVID-19 outbreak. An extremely contagious, respiratory (and possibly enteric) virus, such as SARS-CoV-2, was observed to spread between people directly through contaminated droplets suspended in the air and/or contaminated high-touch environmental surfaces (HITES) and hands directly or indirectly.
The virus deposits on HITES and are then conveyed to susceptible tissues, such as mucous membranes (especially the eyes, nose, and mouth), through the hands. Similar patterns have been noted for other respiratory and enteric viruses, like influenza viruses, rhinoviruses, noroviruses, rotaviruses, and adenoviruses. SARS-CoV-2 can persist on various types of surfaces for minutes to days.
Proper hand hygiene can effectively reduce the number of people who get sick due to diarrhea by 23–40%, reduce diarrheal illness in people with weak or compromised immune systems, reduce respiratory illnesses, like colds, in the general population by 16–21% and reduce rates of absence from school in children by 29–57%.
The components of soap involved in the inactivation and death of microbes
Pathogens are removed from the hand (or any HITES) through thorough lathering and rinsing for appropriate times. The optimum time for handwashing, as recommended by CDC, is between 20-30 seconds. Though there is evidence of the SARS-CoV-2 being sensitive to excess heat, raising the water temperature is not a recommended method of either inactivating or killing the virus.
The components in soap and alcohol-based formulations help to inactivate and kill the virus in different ways. Basic soap mixed with water forms micelles. When one washes their hands with a mixture of soap and water, water dissolves polar (hydrophilic) portions of the dirt or soil load while the soap micelles dissolve the non-polar (hydrophobic) portions of the soil load and lipid-enveloped viruses.
Soap contains a mixture of detergents and surfactants that are capable of disrupting the continuity of the viral envelope by destabilizing the lipid bilayer. They dissolve the envelope within and among the soap micelles, leading to the inactivation of the virus. Once the viral envelope is disrupted, the host-cell receptor-binding ability of the virus is compromised, and the virus can no longer initiate an infection. Thus, enveloped viruses are most effectively removed by washing hands with soap and water. Additionally, chelators in soaps are used to absorb the metal ions which bind the components of the lipid envelopes, making them vulnerable to dissolution through continuous lathering and eventual rinsing. Soaps contain glycerin and pH balancers to ensure moisture retention in the skin.
Antimicrobial (bactericidal and virucidal) soaps contain additional ingredients, such as benzalkonium chloride, benzethonium chloride, chloroxylenol, citric acid, lactic acid, or salicylic acid, which are effective in removing coronaviruses, in general, along with other pathogenic bacteria. Alcoholic formulations like sanitizers, with 60-70% ethanol or isopropyl alcohol, and naturally derived phenols like salicylic acid and thymol have also demonstrated the ability to inactivate and kill enveloped viruses like the SARS-CoV-2.
Hand hygiene is the first and the most critical barrier to disseminating any pathogenic microbe, especially highly contagious viruses like the SARS-CoV-2. Practicing basic hand hygiene, washing hands with soap and water for a minimum of 20 seconds can do wonders in containing the spread of SARS-CoV-2, along with physical distancing and mask-wearing.
- Ijaz MK, Nims RW, Szalay S de, Rubino JR. Soap, water, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2): an ancient handwashing strategy for preventing dissemination of a novel virus. PeerJ. 2021 Sep 17;9:e12041. https://peerj.com/articles/12041/#p-25