It’s Wisdom Wednesday!
Viral diseases pose a serious problem to our public health as they continue to emerge and develop throughout the world. Several epidemics such as the Middle East respiratory syndrome coronavirus (MERS-CoV), severe acute respiratory syndrome coronavirus (SARS-CoV), and H1N1 influenza have been recorded in the last two decades. The most recent viral disease that has been detected is due to a novel coronavirus in Wuhan, China last December 2019. The virus itself is called SARs-CoV-2, while the disease it brings is officially dubbed as the coronavirus disease 2019 (COVID-19).
Presently, the disease has now spread in over 100 locations globally with many countries under lockdown to combat its spread. With that, the World Health Organization (WHO) has declared COVID-19 a pandemic.
The coronavirus is a large family of viruses that causes illness such as respiratory infections to humans and animals. Transmission of this virus is usually between a human and an animal, but it can develop into a person-to-person transmitted disease.
Most viruses have three essential components: nucleic acid (DNA or RNA), proteins, and lipids. COVID-19 is a self-assembled RNA enveloped in glycoproteins, a lipid membrane, and a crown of protein spikes, hence the moniker ‘coronavirus’. The RNA, proteins, and lipids are held together by non-covalent interactions that stick strongly on surfaces. This makes it difficult to remove the virus by washing infected surfaces with water only. Our skin is actually an ideal substrate for viruses because it’s organic and has proteins and fatty acids where the virus can interact and thrive.
Common symptoms of COVID-19 include dry cough, fever, shortness of breath, and tiredness. It takes around 2-14 days from exposure before symptoms manifest. Although the disease is mild especially for young adults and children, severe complications such as pneumonia and multi-organ failure can develop for older people and persons with pre-existing medical conditions such as high blood pressure, heart disease, lung ailments, cancer or diabetes.
To protect yourself from the virus, WHO advises us to regularly wash your hands with soap or with alcohol-based sanitizers.
Soaps are surface-active agents, also known as surfactants, made by hydrolysis of oils and fats such as stearic, palmitic, and oleic acid with sodium or potassium salts (NaOH and KOH). A soap molecule is made of a nonpolar hydrophobic tail (hydrocarbon) and a polar hydrophilic head (-COO–Na+). The head is water-soluble while the tail is soluble in oil/grease.
The way soap cleans many surfaces and our bodies is because of its structure. In the presence of water, the nonpolar tail of the soap molecule attaches itself and dissolves the oil/grease that contains dirt and the polar head remains in the water layer surrounding the oil/grease. The soap molecules arrange themselves around the surface of dirt particles forming micelles. These micelles do not coalesce with each other due to the accumulated negative charge at the surface from the polar head of the soap molecule (-COO–). These micelles are then washed away with water, thus removing dirt from a surface.
Of course, soaps can also be used to remove bacteria and viruses which have lipid (fatty) membranes. The soap can disrupt and break the chemical bonds of those membranes and form micelles around the fragments of the virus or bacterium. In the case of COVID-19, soap is very effective in removing SARs-CoV-2 from our skin and other surfaces. Soap not only breaks the structure of the self-assembled virus but also loosens the strong attachment of the virus on our skin. The friction of washing with soap and water also works to reduce the dirt and other microbes on our skin and other infected surfaces.
Aside from its superior cleaning, antibacterial, and antiviral ability, soap is relatively cheap. It’s abundant and easily accessible; You can find it in supermarkets, drugstores, convenience stores, and even ‘sari-sari’ stores. However, soap is dependent on water to form the micelles and remove dirt and viruses, and not everyone has access to water. Another disadvantage of soap is that it is much less efficient with “hard water” which contains Ca2+ and Mg2+ ions. These ions form insoluble salts with soap (calcium and magnesium soap) which prevents the formation of micelles and are just eventually washed away.
Luckily, there’s another way to clean our hands and protect ourselves from the virus which is alcohol-based sanitizers. Alcohol is an organic compound containing one hydroxyl group (-OH) connected to a saturated carbon atom. The most common alcohols used in hand sanitizers and disinfectants are ethyl and isopropyl alcohols.
Ethyl alcohol (aka ethanol) is a simple, two-carbon alcohol with a hydroxyl group at its end. It is hydrophilic due to the terminal hydroxyl group but also has some nonpolar characteristics due to the hydrophobic carbon chain. On the other hand, isopropyl alcohol (aka isopropanol) is a three-carbon alcohol with a hydroxyl group bonded at the middle carbon atom.
Similar to soaps, the hydrophobic carbon chains in alcohols allow them to dissolve nonpolar compounds like oils; however, unlike soaps, they do not form micelles. Alcohols can denature proteins and dissolve lipids present in bacteria, fungi, and viruses. Moreover, alcohol-based hand sanitizers can be used as is, so there is no need for water! Unless, of course, it’s for the initial dilution.
Speaking of dilution, alcohol-based sanitizers are only effective above 60% concentration. Otherwise, not all the viruses and bacteria will be killed. Concentrations above 70% are also not advised due to the rapid evaporation of the alcohol and the proteins in the virus are not denatured easily in the absence of water. Another problem of alcohol-based sanitizers is that people may not be using enough volume of the sanitizer or they wipe it off before it has dried, reducing the effectiveness of the alcohol. These sanitizers are also not effective against heavily soiled or greasy hands. Moreover, alcohol-based sanitizers are much more expensive compared to soap, and their current supply is limited.
Although this pandemic is certainly scary, we can protect ourselves from it by just washing our hands and other affected surfaces with soap and water. In the case soap and water is unavailable, alcohol-based sanitizers are just as effective. Just remember to fully rub your hands with your choice of disinfectant for at least 20 seconds. Other preventive measures should also be taken such as distancing ourselves from people who are infected, staying at home when we are sick, wearing masks, practicing proper respiratory hygiene (covering our mouths when we cough and sneeze), and keeping up with the latest news regarding COVID-19.
Stay safe. Stay informed. Wash your hands!
References
[1] Charbonneau, D. L., J. M. Ponte, and B. A. Kochanowksi. “A Method of Assessing the Efficacy of Hand Sanitizers: Use of Real Soil Encountered in the Food Service Industry.” Journal of Food Protection 63, no. 4 (April 2000), 495-501. doi:10.4315/0362-028x-63.4.495.
[2] Gold, Nina A., and Usha Avva. Alcohol Sanitizer. Treasure Island (FL): StatPearls Publishing, 2020. https://www.ncbi.nlm.nih.gov/books/NBK513254/.
[3] Hui, David S., Esam I Azhar, Tariq A. Madani, Francine Ntoumi, Richard Kock, Osman Dar, Giuseppe Ippolito, et al. “The continuing 2019-nCoV epidemic threat of novel coronaviruses to global health — The latest 2019 novel coronavirus outbreak in Wuhan, China.” International Journal of Infectious Diseases 91 (2020), 264-266. doi:10.1016/j.ijid.2020.01.009.
[4] Jain, Mahendra. “Oils, Fats, Soaps, Detergents, and Waxes.” Competition Science Vision, November 2007.
[5] Kampf, G. “Efficacy of ethanol against viruses in hand disinfection.” Journal of Hospital Infection 98, no. 4 (2018), 331-338. doi:10.1016/j.jhin.2017.08.025.
[6] Lewis, Ricky. “COVID-19 Vaccine Will Close in on the Spikes.” PLOS Blogs Network | Diverse Perspectives on Science and Medicine. Last modified February 20, 2020. https://blogs.plos.org/dnascience/2020/02/20/covid-19-vaccine-will-close-in-on-the-spikes/.
[7] Mohammed, Manal. “Coronavirus: Not All Hand Sanitisers Work Against It – Here’s What You Should Use.” The Conversation. Last modified March 13, 2020. https://theconversation.com/coronavirus-not-all-hand-sanitisers-work-against-it-heres-what-you-should-use-133277.
[8] Pommerville, Jeffrey C. “A Variety of Chemical Methods can Control Microbial Growth.” In Fundamentals of Microbiology. Burlington: Jones & Bartlett Publishers, 2014.
[9] “Q&A on Coronaviruses (COVID-19).” WHO | World Health Organization. Last modified March 9, 2020. https://www.who.int/news-room/q-a-detail/q-a-coronaviruses.
[10] Stebbins, Samuel, Derek A. Cummings, James H. Stark, Chuck Vukotich, Kiren Mitruka, William Thompson, Charles Rinaldo, et al. “Reduction in the Incidence of Influenza A But Not Influenza B Associated With Use of Hand Sanitizer and Cough Hygiene in Schools.” The Pediatric Infectious Disease Journal 30, no. 11 (November 2011), 921-926. doi:10.1097/inf.0b013e3182218656.
[11] Thordarson, Palli. “Deadly Viruses Are No Match for Plain, Old Soap — Here’s the Science Behind It.” MarketWatch. Last modified March 14, 2020. https://www.marketwatch.com/story/deadly-viruses-are-no-match-for-plain-old-soap-heres-the-science-behind-it-2020-03-08
[12] Zhu, Na, Dingyu Zhang, Wenling Wang, and Xingwang Li. “A Novel Coronavirus from Patients with Pneumonia in China, 2019.” The New England Journal of Medicine, no. 382 (February 2020), 727-733. doi:10.1056/NEJMoa2001017.
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