Corona Virus from a Genetic Perspective
Corona Virus from a Genetic Perspective
COVID-19, or coronavirus is a respiratory virus, meaning it primarily affects the lungs. There has been some confusing terminology used to describe it, which we will clarify. COVID-19 is short for ‘Corona, VIrus, Disease, 2019’ as it started in 2019. The full name is ‘Severe Acute Respiratory Syndrome Coronavirus 2’, which is shortened to ‘SARS-COV-2’.
It is a virus, meaning it cannot reproduce itself on its own, and thus requires a ‘host’ to replicate. It is an RNA virus, so in essence, its genetic code is held on a single strand of RNA. The length of this genetic code is only 30,000 letters long, compared with billions of letters in the human genetic code. In viral terms, it is a strain of the SARS-COV virus family, hence the naming ‘SARS-COV-2’. The original SARS-COV-1 virus, also known simply as ‘SARS’, caused an outbreak of infection in 2003 but was not as severe in its spread. There are in fact seven ‘Coronaviruses’ known to be infectious to humans, four are relatively benign, then there is SARS-COV-1 (2003), MERS-COV (Middle East Respiratory Syndrome) which caused an outbreak in 2012, and now SARS-COV-2 (current outbreak, 2019-2020).
COVID-19 is believed to be ‘zoonotic’ which means it appears to have jumped from a non-human species to cause disease in humans. This zoonotic origin is proposed because it is genetically highly similar to the SARS-COV-2 virus found to infect bats and also pangolins (small anteater mammals). Of particular note, is the slight genetic changes in COVID-19 compared with other SARS-COV viruses that appear to make it very effective in binding to a protein in the lung called ACE2 (Angiotensin Converting Enzyme-2). This high affinity is one of the reasons it seems to be so highly contagious, reflected by its basic reproduction number (amount of new cases caused by a single case) of around three (i.e. one case of infection leads to three more cases of infection).
Finally, some good news is that this current strain of SARS-COV does not appear to be as severe, in general, as the SARS virus of 2003 (in which 20-30% of infected people required assisted ventilation, and the mortality rate was ~10%) [1]. That being said it is now a global pandemic, which has already taken thousands of lives and needs a coordinated world response to ensure the best resolution possible.
References
Centers for Disease Control (CDC), Morbidity and Mortality Weekly Report (MMWR), 2003, https://www.cdc.gov/mmwr/preview/mmwrhtml/mm5228a4.htm
