COVID – 19 [Corona Virus]
Coronaviruses (CoV) are a large family of viruses that cause illness ranging from the common cold to more severe diseases such as Middle East Respiratory Syndrome (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS-CoV). A novel coronavirus (nCoV) is a new strain that has not been previously identified in humans. *WHO
At first, COVID-19 was known as ‘novel coronavirus’, which means a new strain of coronavirus. Once scientists discovered what this strain of coronavirus was and how to identify it in tests, they gave it the name: SARS-CoV-2.3 When someone gets sick with this virus the illness is called COVID-19. For simplicity, the virus and the disease are being referred to by the same name, COVID-19.4
Novel coronavirus (COVID-19) was discovered in 2019 when an unusually high number of people in Wuhan, China, became ill with pneumonia after having an illness similar to the flu. When doctors tested them, they found these people had a type of coronavirus they hadn’t seen before.
The reason COVID-19 is spreading so quickly is simply that it is a new virus the body does not recognise, and as such has little defence against. To explain this further, viruses are proposed to evolve via two mechanisms:
- Antigenic drift: Occurs when small changes (or mutations) in viral genes lead to changes in the surface proteins of the virus, known as hemagglutinin (HA) and neuraminidase (NA).
- Antigenic shift: Occurs when a major change in viral genes creates new HA and/or new NA proteins, resulting in a new virus subtype. Antigenic shift is theorised to occur when a virus from an animal population gains the ability to infect humans — a proposed mechanism behind the origin of COVID-19, which has been linked to a live animal market.6
As a result of this antigenic shift, the body’s immune system may not recognise the surface proteins of the evolved virus, resulting in increased susceptibility to infection. This viral evolution may account for COVID-19’s increased virulence, as this novel virus represents a newly identified pathogen with no known pre-existing immunity in humans.