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Viral variants and strains explained

Your Health / Conditions / COVID-19 / Viral variants and strains explained

Published on Jun 24, 2022
Authored by Dr Cassy Richmond

What is a viral variant?

Viruses are different 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 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 survival mechanism helps many of these viruses with genetic variations, known as variants, stick around in a population longer by helping them to evade the immune system, as well as the impact of available vaccines and treatment options.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 change.

Some viruses are bad at adapting and die off quickly. But others are good - really good. And the good ones create variants that help the virus 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 and quickly that it’s considered a whole new family of viruses, known as a strain. 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 could present similar problems. As the virus that causes COVID-19 spreads, its mutations have led to new variants, such as the Delta and Omicron variants, that could potentially be shown to make the disease more infectious, or even more deadly.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

Researchers are watching variants closely to make sure the vaccines we have remain effective and that scientists can adjust the vaccines as needed to keep up with the changing virus.8                                                                                                                                                                                                                                                     
Just like everything else with the pandemic, this is a constantly evolving situation.8

What you can do to prevent new virus variants from spreading

It is important to follow local health recommendations about vaccination – and speak to your doctor about your eligibility for the COVID-19 vaccine.

Vaccines are available for diseases such as influenza, polio, hepatitis and COVID-19.9 By following your doctor’s instructions about which shots to get, and when to protect yourself and your loved ones, you can play an important role in stopping not only the spread of variants but also their creation.


  1. Sanjuán R., Domingo-Calap P. Mechanisms of viral mutation. Cell Mol Life Sci. 2016;73(23):4433-4448. https://link.springer.com/article/10.1007/s00018-016-2299-6. Accessed 7 Jun 2022. 
  2. How do virus mutations happen, and what do they mean? Ohio State University Wexner Medical Center. https://wexnermedical.osu.edu/blog/virus-mutations-what-do-they-mean. Accessed 14 Jun 2022.
  3. Virus mutations aren’t slowing down. New omicron subvariant proves it. The Washington Post. https://www.washingtonpost.com/health/2022/05/01/coronavirus-more-mutations/. Accessed 14 Jun 2022.
  4. What You Need to Know About Variants. Centers for Disease Control and Prevention. https://www.cdc.gov/coronavirus/2019-ncov/variants/about-variants.html. Accessed 7 Jun 2022.
  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. https://www.cdc.gov/mmwr/pdf/wk/mm5844.pdf. Accessed 7 Jun 2022.
  6.  H1N1 flu (swine flu). Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/swine-flu/symptoms-causes/syc-20378103#:~:text=Overview,those%20of%20the%20seasonal%20flu. Accessed 14 Jun 2022.
  7. SARS-CoV-2 Variant Classifications and Definitions. Centers for Disease Control and Prevention. https://www.cdc.gov/coronavirus/2019-ncov/variants/variant-classifications.html#anchor_1632154493691. Accessed 7 Jun 2022.
  8. Tracking SARS-CoV-2 variants. World Health Organization. https://www.who.int/activities/tracking-SARS-CoV-2-variants. Accessed 14 Jun 2022.
  9. Immunization, Vaccines and Biologicals. World Health Organization. https://www.who.int/teams/immunization-vaccines-and-biologicals/diseases. Accessed 14 Jun 2022.

​​​​​​​External Resources

-Healthdirect: COVID-19
-Australian Government Department of Health: COVID-19 disease, symptoms and variants

PP-PAX-AUS-0170 06/2022

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