Coronavirus: The Basics

In late December of 2019, a disease-tracking system reported mysterious clusters of viral pneumonia in Wuhan, China [1]. Less than a month later, this outbreak of pneumonia became attributed to a complication of a novel virus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This virus leads to the disease that is currently taking a heavy toll on individuals all across the globe, known as coronavirus disease 2019 (COVID-19).

written & illustrated by emily sun July 24, 2020

what’s the difference between COVID-19 and SARS-CoV-2?

Although COVID-19 and SARS-CoV-2 are commonly thrown together in the media, they are not interchangeable. SARS-CoV-2 is the name of the specific virus which causes COVID-19. Wait, there’s a different name for the virus and the disease? It may sound baffling at first, but there is a rationale for this naming system.

Viruses refer specifically to the germs that hijack host cells in order to replicate within them, and they are only composed of two things: genetic material and an outer envelope formed by organic molecules [2]. Virus names inform scientists about the specific genetic structure of virus species, facilitating the development of drug treatment and vaccinations [3]. For example, SARS-CoV-2 is named after the SARSCoV virus due to their genetic similarities, but they cause distinct illnesses and should not be confused [3].

A germ’s capacity to cause infection in host cells is known as its pathogenicity, and the more pathogenic a virus is, the higher its ability to invade cells [4]. Most viruses, including SARS-CoV-2, are considered pathogenic in nature. Initially, when a virus enters the body, the immune system tries to fight it off; if a virus disrupts the normal bodily functions, however, the host may feel unwell— this condition is referred to as the “disease” caused by the virus. Disease names like “COVID-19” tend to be more familiar to the public than their virus counterparts and are typically used for classifying factors such as spread and transmissibility [3].

where did coronavirus get its name?

As it turns out, the term “coronavirus” did not come from a beer. Its title comes from the crown, or “corona,” which seems to surround the virus when viewed under a microscope [5]. This appearance is due to protein-based spikes, or peplomers, on the outer layer virus envelope, which bind to specific receptors in host cells [5]. “Coronavirus” is an umbrella term referring to a whole group of viruses with this unique feature, and the new SARS-CoV-2 is just one of the seven known human coronaviruses [6].

Coronaviruses are nothing new: in fact, they are found in animals frequently exposed to humans, including a variety of farm animals, domestic pets, and small rodents [7]. The first human case of infection by a coronavirus was reported in the mid-1960s after a respiratory sample was taken from a patient with the common cold [8]. Ultimately, scientists found that coronaviruses caused up to 15 percent of common cold cases at the time [8]. While these coronavirus strains seemed both mild and manageable, the first major human coronavirus outbreak from SARS-CoV in the early 2000s proved alarmingly fatal and is thought to have jumped into the population indirectly from bats [9]. These newer coronavirus outbreaks shed light on the alarming risks that these viruses are starting to pose for humans.

what does SARS-CoV-2 do to the body?

In the journey to develop treatment for the novel coronavirus, scientists discovered a protein crucial to virus entry, called angiotensin-converting enzyme 2 (ACE-2) [10]. This protein normally aids in circulatory system regulation, meaning it is present in most tissue throughout the body; however, it is most concentrated in areas including the lower respiratory tract, kidneys, heart, and gastrointestinal tract [10,11]. This is why infected patients may not only display respiratory illness, but they can also experience other complications regarding digestion, kidney, and heart function [11].

When SARS-CoV-2 infiltrates the human body, a sequence of steps takes place. First, spike proteins on the virus bind to ACE-2 receptors on the host cell membrane; second, the virus enters the host cell through an uptake process called endocytosis; third, the virus and host cell membranes fuse, allowing the release of viral genetic material (RNA) into the host cell; and fourth, RNA is replicated in different regions of the host cell to form fully-fledged viruses, which are then released from the host cell to continue the cycle (see figure) [9]. Better understanding of the interaction between the spike proteins and ACE2 binding site may allow for the development of neutralizing antibodies, or substances that bind to the virus particle and take away its ability to interact with other cells [9]. In SARS-CoV-2, for example, a neutralizing antibody that binds to the spike protein would successfully inhibit its ability to bind to and enter host cells. This knowledge may also help specialists quickly target SARS-CoV-2 mutant strains and other related viruses due to their genetic and structural similarities. COVID-19 is now the third major outbreak of coronaviruses in humans. Although the disease causes symptoms resembling the flu for the majority of the population, old age and underlying health conditions pose a risk for severe complications. The Centers of Disease Control and Prevention (CDC) recommends wearing a face covering, frequent hand-washing, and social distancing of at least six feet to suppress virus transmission [12]. It is crucial that these precautions are taken seriously, especially as scientists dig deeper into the nature of this disease and the virus which causes it.

references

[1] Li et al. (2020). Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus–Infected Pneumonia. New England Journal of Medicine, 382(13), 1199-1207. doi:10.1056/nejmoa2001316 [2] Virus (n.d.). In Merriam-Webster.com. Retrieved from https://www. merriam-webster.com/dictionary/virus [3] World Health Organization. (2020). Naming the coronavirus disease (COVID-19) and the virus that causes it. Retrieved from https:// www.who.int/emergencies/diseases/novel-coronavirus-2019/technical-guidance/naming-the-coronavirus-disease-(covid-2019)-and-thevirus-that-causes-it [4] Pathogenic (n.d.). In Vocabulary.com Online Dictionary. Retrieved from https://www.vocabulary.com/dictionary/pathogenic [5] Centers for Disease Control and Prevention. (2019). World MERSCoV Photos. Retrieved from https://www.cdc.gov/coronavirus/mers/ photos.html [6] National Center for Health Statistics, Centers for Disease Control and Prevention. (2020). Human Coronavirus Types. Retrieved July 15, 2020, from https://www.cdc.gov/coronavirus/types.html [7] Saif, L.J. (2004). Learning from SARS: Preparing for the Next Disease Outbreak: Workshop Summary. National Academies Press (US). Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK92442/ [8]Petersen et al. (2020). Comparing SARS-CoV-2 with SARS-CoV and influenza pandemics. The Lancet Infectious Diseases. doi:10.1016/ s1473-3099(20)30484-9 [9] Jiang, S., Hillyer, C., & Du, L. (2020). Neutralizing Antibodies against SARS-CoV-2 and Other Human Coronaviruses. Trends in Immunology, 41(5), 355-359. doi:10.1016/j.it.2020.03.007 [10] Tikellis, C., Thomas, M. C. (2012). Angiotensin-Converting Enzyme 2 (ACE2) Is a Key Modulator of the Renin Angiotensin System in Health and Disease. International Journal of Peptides, 2012, 1-8. doi:10.1155/2012/256294 [11] Astuti, I., Ysrafil. (2020). Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2): An overview of viral structure and host response. Diabetes & Metabolic Syndrome: Clinical Research & Reviews, 14(4), 407-412. doi:10.1016/j.dsx.2020.04.020 [12] World Health Organization. (2020).How to Protect Yourself & Others. Retrieved July 15, 2020, from https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/prevention.html