Introduction to COVID-19
On March 11th, 2020, the World Health Organization (WHO) declared COVID-19 a pandemic. Many people did not anticipate that, more than 22 months later, daily routines once considered standard would still be in upheaval. While widespread vaccination efforts have been a step in the right direction, much of the world still finds itself struggling to control COVID-19. There is still considerable uncertainty of what the post-pandemic world will look like, particularly in light of the emergence of new variants. By now, most people have been sufficiently bombarded by COVID-19 related news reporting the number of new cases, vaccine efficacy reports, percentage of vaccine coverage, and how overwhelmed healthcare systems are around the world. With so much information available on the internet, perhaps now is a good opportunity for us to take a step back and re-visit the basics of COVID-19.
COVID-19, short for coronavirus disease 2019, is an infectious disease caused by a novel coronavirus named SARS-CoV-2. SARS-CoV stands for “severe acute respiratory syndrome coronavirus.” This is already the third human coronavirus to emerge in the past two decades, the first being SARS-CoV-1, responsible for the 2002 SARS outbreak, and the second being Middle East Respiratory Syndrome-related Coronavirus (MERS-CoV). While a tremendous amount of new information is being published each week, four of the topics most relevant to the public are: 1) Current state of COVID-19, 2) Clinical presentation of COVID-19, 3) Differential impact of COVID-19 based on patient-specific factors, and 4) Prevention and treatment of COVID-19.
1) Current State of COVID-19
According to the WHO, there were 267,865,289 confirmed COVID-19 cases and 5,285,888 deaths globally as of December 10, 2021, converting to a death rate of 1.97%. The virus can be transmitted in several ways including close contact, airborne transmission, and contaminated surfaces. Therefore, public health experts have stressed the importance of physical distancing, mask wearing, and other general hygiene measures. The rapid and sustained global spread of the SARS-CoV-2 has also been facilitated by the emergence of several mutations of the virus. Currently, there are five key Variants of Concern (VOC) named Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2), and Omicron (B.1.1.529). These variants have different characteristics such as varying infection rates and disease severity, and are of particular concern when discussing their impact on the effectiveness of commercially available vaccines and therapies. Further details on variants and their impact will be discussed more in detail in a subsequent blog.
2) Clinical Presentation of COVID-19
As many will recall, one of the key issues raised at the beginning of the pandemic was that the many overlapping symptoms of COVID-19 were difficult to distinguish from other respiratory diseases such as the common cold or influenza. To help understand and distinguish between common respiratory diseases, a summary of symptoms of the common cold, influenza, and COVID-19 is shown below.
Source: ahs.ca/covid
3) Differential Impact of COVID-19 Based on Patient-Specific Factors
It has been well-described that certain groups of people are more likely than others to get severely ill from COVID-19. These groups include, but are not limited to:
· Older adults ≥65 years
· Adults with:
o Cancer
o Chronic kidney or lung disease
o Dementia or other neurological conditions
o Type 1 or 2 diabetes
o Down syndrome
o Heart conditions
o HIV infection
o Immunocompromised state (weakened immune system)
o Liver disease
o Overweight and obesity
o Pregnancy
o Sickle cell disease or thalassemia
o Smoking (current or former)
o Solid organ or blood stem cell transplant
o Stroke or cerebrovascular disease
o Substance use disorders
Importantly, people with such pre-existing conditions have been found to also have higher risk of death from COVID-19 compared to those with no pre-existing conditions. The risk of death also increases as the number of comorbid conditions increases.
Table adopted from the CDC
Additionally, age has also been consistently highlighted as an important differentiator in terms of risk of infection, hospitalization, and death.
Table adopted from the CDC comparing the rate of cases, hospitalizations and death to that of 18–29-year-olds (reference group). A rate of 1X indicates there is no difference compared to the 18-29 year-old category.
4) Prevention and Treatment Against COVID-19
Thanks to a global collaborative effort, several vaccines have been made to help reduce the symptoms and/or severity of COVID-19 and have been distributed to many countries across the globe, with over 7.7 billion doses administered globally as of November 29, 2021. While vaccines have seemed like the light at the end of the tunnel for many, there has also been a shadow of caution as variants of concern (mutated versions of SARS-CoV-2) have impacted the effectiveness of commercially available vaccines. So, what else do we need to control the pandemic? Stay tuned for the next blog with more discussions on variants, their impact on vaccines, and the next layer of protection and treatment needed to fight COVID-19.
References
1. Alberta Health Sciences. COVID-19 symptoms in comparison to the flu and the common cold. Accessed June 12, 2021. https://www.albertahealthservices.ca/assets/info/ppih/if-ppih-covid-19-flu-cold.pdf
2. Centers for Disease Control and Prevention. How COVID-19 Spreads. Updated May 13, 2021. Accessed June 23, 2021. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/how-covid-spreads.html
3. Centers for Disease Control and Prevention. People with certain medical conditions. Updated May 13, 2021. Accessed June 23, 2021. https://www.cdc.gov/coronavirus/2019-ncov/need-extra-precautions/people-with-medical-conditions.html
4. Centers for Disease Control and Prevention. Risk for COVID-19 infection, hospitalization, and death by age group. Updated November 22, 2021. Accessed December 12, 2021. https://www.cdc.gov/coronavirus/2019-ncov/covid-data/investigations-discovery/hospitalization-death-by-age.html
5. Centers for Disease Control and Prevention. Underlying Medical Conditions. Updated October 14th, 2021. Accessed December 12, 2021. https://www.cdc.gov/coronavirus/2019-ncov/hcp/clinical-care/underlyingconditions.html
6. Davies NG, Abbott S, Barnard RC, et al. Estimated transmissibility and impact of SARS-CoV-2 lineage B.1.1.7 in England. Science. 2021;372(6538):eabg3055.
7. Faria NR, Mellan TA, Whittaker C, et al. Genomics and epidemiology of a novel SARS-CoV-2 lineage in Manaus, Brazil. Preprint. medRxiv. 2021;2021.02.26.21252554.
8. Horby P, Huntley C, Davies N, et al. NERVTAG note on B.1.1.7 severity for SAGE77. Accessed June 23, 2021. https://app.box.com/s/3lkcbxepqixkg4mv640dpvvg978ixjtf/file/768458300892
9. Volz E, Mishra S, Chand M, et al. Transmission of SARS-CoV-2 Lineage B.1.1.7 in England: Insights from linking epidemiological and genetic data. Accessed June 23, 2021. https://www.imperial.ac.uk/media/imperial-college/medicine/mrc-gida/2020-12-31-COVID19-Report-42-Preprint-VOC.pdf
10. Pearson CAB, Russell TW, Davies N, et al. Estimates of severity and transmissibility of novel SARS-CoV-2 variant 501Y.V2 in South Africa. Published January 11, 2021. Accessed June 23, 2021. https://cmmid.github.io/topics/covid19/sa-novel-variant.html
11. World Health Organization. Listings of WHO’s response to COVID-19. Published June 29, 2020. Accessed June 23, 2021. https://www.who.int/news-room/detail/29-06-2020-covidtimeline.
12. World Health Organization. WHO issues its first emergency use validation for a COVID-19 vaccine and emphasizes need for equitable global access. Published December 31, 2020. Accessed June 23, 2021. https://www.who.int/news/item/31-12-2020-who-issues-its-first-emergency-use-validation-for-a-covid-19-vaccine-and-emphasizes-need-for-equitable-global-access..
13. World Health Organization. WHO Coronavirus (COVID-19) Dashboard. Updated December 10, 2021. Accessed December 12, 2021.
https://covid19.who.int/
14. World Health Organization. Weekly epidemiological update on COVID-19. Updated June 22, 2021. Accessed June 23, 2021. https://www.who.int/publications/m/item/weekly-epidemiological-update-on-covid-19---22-june-2021
15. World Health Organization. Tracking SARS-CoV-2 variants. Updated November 29, 2021. Accessed November 29, 2021. https://www.who.int/en/activities/tracking-SARS-CoV-2-variants/
16. Worldometer. Age, sex, existing conditions of COVID-19 cases and deaths. Updated May 13, 2021. Accessed June 23, 2021. https://www.worldometers.info/coronavirus/coronavirus-age-sex-demographics/
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