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Covid-19

Understanding the facts

the bigger picture

What is covid-19?

The causative agent of the novel coronavirus disease 2019 (COVID-19) is a new strain of severe acute respiratory coronavirus-2 (SARS-CoV-2); a positive-sense single-stranded RNA with the largest known RNA genome.[5] Is an intracellular pathogen affecting susceptible hosts.[1] Its entry is mediated by a human host cell-surface receptor, angiotensin-converting enzyme-2 (ACE2), found in the lower respiratory tract human on which binds the SARS-CoV-2 spike (S) protein - triggering the host’s immunological response.[2] A hyperactive immune response is prevalent in severe cases of Covid-19 patients.[3]

Pandemics in the context of Climate change: Why we need to be aware of the greater risks of Pandemics in the future: COVID-19 and the bigger picture: 

Disturbances in ecosystems because of increased need for food production, extensive agricultural activities and re-distribution of disease reservoirs – all contributed to climate change and the pandemic the world is facing right now.[1] Moreover, the increase of globalisation and travel facilitated the ideal pathway for a zoonotic agent to transmit easier from its original host to others around the world. While many viruses may not cause any disease in their natural or intermediate hosts (e.g., allegedly bats, and pangolins, respectively) the severity of disease and mortality rate increased significantly once is transmitted to the human host. [1, 2] The shared genetic similarities of the bat-like derived SARS-CoV-2 and the novel virus, suggest its zoonotic origin.[5] 

What do we mean by a new variant of a virus?

The European Centre for Disease Prevention and Control defined a new variant as a new lineage of the virus. Mutations are genetic changes in the spike protein which are specific to each variant (See table below for the number of mutations per variant). https://www.ecdc.europa.eu/en/covid-19/variants-concern 

These changes can influence the properties of the virus in evading the host’s immunity and reduced sensitivity to neutralising antibodies, transmissibility and infection severity. New variants can also have an epidemiological influence – the incidence, distribution and the control of the disease. The table below shows some closely observed variants and their implications in terms of pathogenesis or the ability of the virus to cause disease, its infection severity and transmissibility from person to person. However, many more have been detected and are under investigation. 

How is Covid-19 similar to past viruses? 

 The causative viruses of previous epidemics such as SARS-CoV and MERS-CoV share a genomic (79.5%) and protein similarities (95-100%) with SARS-CoV-2.[2] 

  1. Slingenbergh J, Gilbert M, de Balogh K, Wint W. Ecological sources of zoonotic diseases. Rev. sci. tech. Off. int. Epiz., 2004; 23 (2): 467-484. https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.664.7668&rep=rep1&type=pdf 

  2. Amawi H, Deiab G A, Alijabali A A A, Dua K, Tambuwala M. COVID-19 pandemic: an overview of epidemiology, pathogenesis, diagnostics and potential vaccines and therapeutics. Future Science. 2020: 11(4). https://doi.org/10.4155/tde-2020-0035 

  3. Kumar A, Prasoon P, Kumari C, Pareek V, Faiq M A, Narayan R K, Kulandhasamy M, Kant K. SARS-CoV-2-specific virulence factors in Covid-19. J Med Virol. 2021; 93: 1343-1350. DOI: 10.1002/jmv.26615 

  4. Riley E M. COVID-19 vaccines: how did we do so well?. Trends in Urology & Men’s Health. 2021; 12 (3). 5. 

  5. Romano M, Ruggiero A, Squeglia F, Maga G, Berisio R. A Structural View of SARS-CoV-2 RNA Replication Machinery: RNA Synthesis, Proofreading and Final Capping. Cells. 2020; 9(5): 1267. https://dx.doi.org/10.3390%2Fcells9051267 

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