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HomeYour HealthConditionsViral IllnessesViral Variants And Strains ExplainedViral Variants And Strains Explained

Published on May 10, 2023

Authored by Dr Cassy Richmond

Since the start of the pandemic, we have all been exposed to a plethora of new words and concepts (think: rapid antigen testing, working from home (WFH), variants and variants of concern). Whilst COVID testing and 'WFH' are concepts that many of us are familiar with now, what are a 'variants' and 'variants of concern'?

What Is A Viral Variant?

Viruses may differ from one another in many ways, including how efficiently they spread and which parts of the body they attack. One thing most viruses have in common, though, is that they have resourceful ways to survive. As they infect and reproduce (or multiply) in living things, their genetic makeup can adapt. Some changes, or mutations, can cause a virus to be more contagious (i.e. move from host to host more efficiently) or make the host more sick. This mechanism helps many viruses with genetic variations (known as variants) to stick around in a population longer by helping them to evade the immune system, and may also affect the impact of available vaccines and treatments.1,2

The ongoing genetic change in viruses is one of the main reasons we need to get an adapted flu shot each year - and one of the factors that makes eradicating COVID-19 a challenge.1,3

What Causes Variants in Viruses?

Viruses constantly change through mutation, and, in some cases, these mutations result in the formation of a new variant of the virus.4 Think of this process as a bit like a photocopy: when you copy a document, there’s always a chance that errors happen - like when text gets cut off or becomes too faded to read. The more you copy the copies, the more significant these errors become.

Similarly, viruses can develop progressively more adaptations each time it replicates over and over again.

Some viruses are not successful at adapting and die off quickly. But others are quite effective at this - which help the virus to survive and infect more living beings so that it can continue to spread and mutate over time.1,2

When Do Viral Variants Become Concerning?

Sometimes a virus can mutate so drastically that it becomes a whole new strain of the virus. This happened when a new influenza A virus (called H1N1) appeared, causing the 2009 swine flu pandemic. At the time, the seasonal flu shot didn’t help curb the spread because it was not designed to protect people from that specific variant of the flu virus.5,6

The COVID-19 variants pose a similar problem. As the virus that causes COVID-19 spreads, its mutations have led to new variants, such as the Delta and Omicron variants.4,7 When a new variant is found to have increased transmissibility (i.e. it is more infectious), or it causes more severe illness, then it may be referred to as a variant of concern.8

Just like everything else with the pandemic, this is a constantly evolving situation and is being monitored closely.8


  1. Sanjuán R., Domingo-Calap P. Mechanisms of viral mutation. Cell Mol Life Sci. 2016;73(23):4433-4448. Accessed 9 May 2023. 

  2. How do virus mutations happen, and what do they mean? Ohio State University Wexner Medical Center. Accessed 9 May 2023. 

  3. Virus mutations aren’t slowing down. New omicron subvariant proves it. The Washington Post. Accessed 9 May 2023. 

  4. Variants of the virus. Centers for Disease Control and Prevention. Accessed 9 May 2023.

  5. Effectiveness of 2008–2009 Trivalent Influenza Vaccine Against 2009 Pandemic Influenza A (H1N1) – United States, May–June 2009. Centers for Disease Control and Prevention. MMWR. 2009;58(44):1241-1245. Accessed 9 May 2023. 

  6. H1N1 flu (swine flu). Mayo Clinic.,those%20of%20the%20seasonal%20flu. Accessed 9 May 2023. 

  7. SARS-CoV-2 Variant Classifications and Definitions. Centers for Disease Control and Prevention. Accessed 9 May 2023. 

  8. Tracking SARS-CoV-2 variants. World Health Organization. Accessed 9 May 2023. 

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