Transmission and prevention of COVID-19
By Alfred Sibanda T.
Way before the proposition of the germ theory of disease by Louis Pasteur, infectious diseases were known and people did all that they could to try and prevent themselves from getting them. Many of us are familiar with how the Biblical lepers were isolated from society because everyone feared getting the disease. Well, today we know that leprosy is not as infectious as it was thought to be but nonetheless, the point remains, people tried as much as they could to prevent infection by leprosy. Over the years, we have learnt and we continue to learn the various ways in which infectious diseases are transmitted from one individual to another. In this process of learning, many lives have been lost. It is our duty as humans to make it a point to learn the various ways in which disease is passed from one individual to the next for protection of both ourselves and others. In this period of time when the world is experiencing a devastating outbreak of COVID-19, learn how you can protect yourself and others from getting infected. In this article, we discuss the modes of transmission of COVID-19 and how we can protect ourselves from getting the disease.
The entire spectrum of the ways in which COVID-19 is transmitted from one person to another is yet to be confirmed but we now have a reasonable amount of information as to the measures we can put in place to prevent getting the disease and these have been proven to be effective. The SARS-CoV-2 has been shown to be transmissible via respiratory droplets. These can be released from an infected person to an uninfected person through coughing, breathing, sneezing, laughing, singing etc. Naïve exchanges of body secretions like saliva and mucus is also a big risk factor for transmission of the virus. The currently accepted definition of a droplet is a secretion that is mostly water but with various inclusions like electrolytes, cells and infectious agents such as viruses, bacteria and fungi. These are transmissible over short distances since they are heavy and thus quickly succumb to the earth’s gravitational pull. It is thus advised to physically distance yourself by at least one meter from other people in order to avoid being infected. If physical distancing is not possible, it is advised to always wear a fabric mask in order to prevent any droplets from reaching one’s mucosal surfaces.
The virus can also be transmitted directly from one person to another if the infected person touches their infected respiratory secretions and passes these on to another person via common practices like handshaking and playful touching etc. if peradventure the recipient then also touches their face, they can then inoculate themselves with the virus when they touch their eyes, mouth or nose.
A study by Yen Lee Angela Kwok et al. showed that on average, people touch their face approximately 23 times per hour. Of these touches, approximately 44% involves contact with a mucosal membrane. This is a frighteningly high statistic especially in these times when the world is facing a respiratory virus pandemic and also considering how unlikely it is that people wash their hands this often in the hour. It has been recommended that we wash our hands at least six times a day in order to effectively reduce our chances of catching the coronavirus. This should also be coupled with a reduction in the number of times we touch our face. Experts suggest that wearing gloves can reduce the number of times you touch your face as you will be more aware of your hand’s movements towards the face.
Another way in which COVID-19 is transmitted is through fomites. Fomites are contaminated surfaces, say touched, sneezed or coughed on by an infected person. If another person touches this surface, they take the infection and can inoculate themselves with the infected respiratory secretions if they are careless enough to then touch their face afterwards without having washed their hands with soap or alcohol. In this light, it is advised that we regularly clean surfaces that are exposed to our secretions or hands, such surfaces as door handles, laptops, television remote controllers, pens, tables, chairs etc.
Handwashing and cleaning of surfaces should be done with soap or alcohol and here is why:
Viruses can either be enveloped or non-enveloped. Non-enveloped viruses are designed to survive outside the body and may be difficult to kill, whereas enveloped viruses, such as coronaviruses, have a phospholipid envelope covering. This envelope, being made up of phospholipids, has hydrophobic (water-hating) and hydrophilic (water loving) components. These two opposite components are normally arranged in a manner such that the hydrophilic ends are facing a water environment whereas the hydrophobic parts are in their own non-aqueous environment. This creates an arrangement that is referred to as the bilayer arrangement. Now, if soap or alcohol is used to wash off the virus, it essentially distorts the structure of the virus envelope and remember we said that the envelope protects the contents of the virus so if the envelope is destructed, the rest follows as it is now exposed. This is much like how we often use soap to wash our hands when we have just had a fatty meal such as potato chips, beef and chicken etc. If you wash your hands without any soap, you are unlikely to remove all the annoying fat from your hands.
Alcohol is an organic solvent and it interacts with long chain carbon molecules such as those in the coronavirus’ lipid envelope and this dissolves the membrane leading to similar effects. The proper handwashing procedure should also be used to ensure that all the virus particles are effectively removed.
With many infectious diseases, a critical area of research is always whether a disease can be transmitted from a mother to her child through either the trans-placental route or in breast milk. Although studies have shown that breast milk from an infected mother indeed contains SARS-CoV -2 RNA, this hasn’t been shown to be viable. A few studies however suggest that it is possible for the virus to be transmitted trans-placentally.
Transmission in the hospital
The hospital is an environment for the sick and this means that extra caution has to be taken in order to prevent transmission of the coronavirus between patients. Patients should be adequately distanced from one another and not crowded as this increases their risk of catching the disease. The rooms should be adequately ventilated as well and all COVID-19 prevention protocol observed.
In all the infectious disease outbreaks that have occurred and in any to come, if any, health workers are constantly exposed to the disease, they are always in direct contact with the disease as they provide care for those who are unfortunate enough to have caught the disease. Even though the work of medical and research personnel is to provide solutions for the sick, we have none to a few people like Jesse William Lazear, the epidemiologist who in an attempt to study the transmission of yellow fever and malaria, allowed himself to be bit by an infected mosquito in order to observe the effects. Lazear died of yellow fever at just 34 years of age as a result of this feat. We could say he took one for science, he died for the cause of science and today we have valuable knowledge of these diseases partly because of him. But again, this is not how science normally works today, the people who are trying to figure out how to deal with coronaviruses are advised to take necessary precaution when handling patients in order to protect themselves and others around them. In this light, medical personnel should always wear Personal Protective Equipment (PPE) when working with patients. This includes a gown, goggles, a mask and face shield etc. this is especially important when performing Aerosol Generating Procedures. These are mainly surgical procedures which often cause release of aerosols from the patient into the environment and hence, without PPE, medical personnel can inhale these and catch the disease. Aerosol Generating procedures (AGPs) include: intubation, extubation, nebulisation, chest compressions, sputum induction, bronchoscopy, dental procedures, endoscopy etc.
Quarantine and isolation have been used for over 500 years now as a way to control the spread of infectious disease. In the years 1347-1352, the world witnessed a pandemic of plague, caused by Yesinia Pestis. This disease was being spread by sailors as they moved from one area to another. It spread through Italy, to France and Spain, then through to Central Europe. There was no medicine that could treat the plague and so the only hope to control this pandemic was to restrict human interactions. This began being implemented in some states where strangers were prevented from entering their cities. There was also separation of healthy and infected individuals. Quarantine was first introduced in the year 1377 in Croatia and the first permanent plague hospital opened by the republic of Venice in 1423 on the small island of Santa Maria di Nazareth (Eugenia Tognotti, 2013). Sailors coming from affected areas were first subjected to a forty day quarantine and isolation. This effectively reduced the spread of the disease. All through the subsequent outbreaks of the dreaded Cholera and influenza, quarantine has become an effective way to control the spread of infection and today is no exception.
It is of utmost importance during this pandemic for everyone to minimise movement to crowded places and to stay at home. Places where it is risky to travel to include bars, churches, weddings, gyms and sporting events. For example, in churches, practices such as singing and shouting can mean prolonged exposure to respiratory droplets and hence more chances of catching the coronavirus. Many governments the world over have indeed put in place measures to minimize movement, allowing only the essential workers to continue going to work and everyone else to work from home if possible.
WHO Guidelines for prevention of COVID-19
The World Health Organisation has published some guidelines that can be used in order to prevent oneself from catching the coronavirus or transmitting it to others and these include:
- Staying at home if feeling unwell and contacting your doctor (from home) for help
- Health workers should use Personal Protective equipment
- Make sure there is good ventilation in your home and work offices.
- Limit your contact with other people, distance yourself by at least a meter.
- Identify anyone who is infected so that they can be quickly isolated and prevented from spreading the disease.
Who transmits the disease?
The SARS-CoV-2 is transmitted from an infected person to a second person. Asymptomatic and presymptomatic individuals can transmit the disease. A presymptomatic individual is one who has not yet developed symptoms but has already been infected. An asymptomatic individual is one who does not develop any symptoms of disease even though they have been infected. The importance of this fact is to highlight that we should still observe precautionary measures even if we are around people who seem to be well and unaffected. It has been shown however that a presymptomatic individual has a higher chance of transmitting the disease as compared to an asymptomatic individual although this should make no difference in the way we interact with people during this pandemic.
Tognotti E. Lessons from the history of quarantine, from plague to influenza A. Emerg Infect Dis [Internet]. 2013 Feb (accessed on 28 July 2020). http://dx.doi.org/10.3201/eid1902. 120312
World Health Organisation. Q&A: How is COVID-19 transmitted? 9 July2020. https://www.who.int/news-room/q-a-detail/q-a-how-is-covid-19-transmitted (accessed 28 July 2020)
European Centre for Disease Prevention and Control, Transmission of COVID-19. 16 July 2020. https://www.ecdc.europa.eu/en/covid-19/latest-evidence/transmission (accessed 28 July 2020)
World Health Organisation. Transmission of SARS-CoV-2: implications for infection prevention precautions. 9 July 2020. https://www.who.int/news-room/commentaries/detail/transmission-of-sars-cov-2-implications-for-infection-prevention-precautions (accessed 28 July 2020).
Khai Tran et al. Aerosol Generating Procedures and Risk of Transmission of Acute Respiratory Infections to Healthcare Workers: A Systematic Review. Published online 2012 Apr 26. doi: 10.1371/journal.pone.0035797.PMCID: PMC3338532.PMID: 22563403.
Davies A, Thomson G, Walker J, Bennett A. A review of the risks and disease transmission associated with aerosol generating medical procedures. Journal of Infection Prevention. 2009;10:122–126.
Gamage B, Moore D, Copes R, Yassi A, Bryce E, et al. Protecting health care workers from SARS and other respiratory pathogens: a review of the infection control literature. Am J Infect Control. 2005;33:114–121
Centers for Disease Control and Prevention. Public health guidance for community-level preparedness and response to severe acute respiratory syndrome (SARS). Supplement I: infection control in healthcare, home, and community settings. Atlanta (GA): CDC. 2005;18 Available: http://www.cdc.gov/ncidod/sars/guidance/I/index.htm
https://www.health.nsw.gov.au/Infectious/tuberculosis/Pages/tb-sputum-induction-guidelines.aspx (accessed 29 July 2020)
Caroline A O’Neil et al. Characterization of Aerosols Generated During Patient Care Activities. Clin Infect Dis. 2017 Oct 15; 65(8): 1342–1348. Published online 2017 Jul 31. doi: 10.1093/cid/cix535. PMCID: PMC6248660.PMID: 29017249.
World Health Organization. Infection prevention and control of epidemic-and pandemic-prone acute respiratory infections in health care: WHO guidelines. Geneva, Switzerland: WHO, 2014.
Siegel JD, Rhinehart E, Jackson M, Chiarello L; Health Care Infection Control Practices Advisory Committee 2007 guideline for isolation precautions: preventing transmission of infectious agents in health care settings. Am J Infect Control 2007; 35:S65–164
Booth TF, Kournikakis B, Bastien N, et al. Detection of airborne severe acute respiratory syndrome (SARS) coronavirus and environmental contamination in SARS outbreak units. J Infect Dis 2005; 191:1472–7.
Panzac D. Quarantines and lazarettos: Europe and the plague of the East, XVII–XX centuries [in French]. Aix-en-Provence (France): Éditions Édisud; 1986. p. 173–6.
https://www.historyofvaccines.org/index.php/content/jesse-lazear (accessed 29 July 2020)
Mafart B, Perret JL. History of the concept of quarantine [in French] Med Trop (Mars). 1998;58(Suppl):14–20
Bowsky WM. The impact of the Black Death upon Sienese government and society. Speculum. 1964;39:1–34 10.2307/2850126
Municipality of Venice, editor. Venice and plague 1348/1797 [in Italian]. Venice (Italy): Marsilio; 1979
https://www.who.int/medical_devices/meddev_ppe/en/ (accessed 29 July 2020)
Kiona N. Smith. The Epidemiologist Who Killed Himself For Science. Forbes 2017.
https://www.ncbi.nlm.nih.gov/books/NBK143281/ (accessed 28 July 2020)
Kwok YL, Gralton J, McLaws ML. Face touching: a frequent habit that has implications for hand hygiene. Am J Infect Control. 2015;43(2):112-114. doi:10.1016/j.ajic.2014.10.015
https://www.bbc.com/news/health-52720089 (accessed 29 July 2020)
Vivanti, A.J., Vauloup-Fellous, C., Prevot, S. et al. Transplacental transmission of SARS-CoV-2 infection. Nat Commun 11, 3572 (2020). https://doi.org/10.1038/s41467-020-17436-6.
https://www.clinicaladvisor.com/home/topics/infectious-diseases-information-center/combating-covid-19-best-practices-that-clinicians-need-to-know/ (accessed on 14 August 2020)