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COVID-19 is an infectious respiratory disease caused by the SARS-CoV-2 coronavirus ^(1)(2)(3). Contrary to rumours circulating, this disease is not the same as the flu – it’s caused by a different virus⁽¹⁾⁽³⁾.

Join us to learn more about coronaviruses, flu viruses and their diseases.

Understanding coronaviruses, including SARS-CoV-2

SARS-CoV-2 is a virus belonging to the Coronaviridae family ⁽¹⁾⁽⁴⁾. Coronaviruses are relatively simple structures: spherical and coated with spikes of protein that help the virus bind to and infect healthy cells ⁽²⁾. When seen under a powerful microscope, the spikes look like a crown, hence their name since corona is Latin for ‘crown’ ⁽²⁾. There are four different types of coronavirus: alphacoronaviruses, betacoronaviruses, gammacoronaviruses and deltacoronaviruses. SARS-CoV-2 is a betacoronavirus ⁽⁵⁾.

Coronaviruses are known to cause respiratory and intestinal infections in both animals and humans ⁽¹⁾. To date, seven coronaviruses have been found to cause infections in humans ⁽⁴⁾. SARS-CoV-2 was not found in humans before the current COVID-19 outbreak ⁽¹⁾. It is believed that SARS-CoV-2 was introduced to human populations during November or December 2019, with the first cases of COVID-19 appearing around the end of December ⁽⁶⁾.

Although there have been previous outbreaks of coronavirus diseases in humans, there were no effective vaccines or drugs available to prevent or cure COVID-19 when the novel coronavirus SARS-CoV-2 outbreak first occurred ⁽⁵⁾.

Understanding flu viruses

Flu viruses belong to the Orthomyxoviridae family ⁽⁴⁾. There are four different types: A to D. Only type A and type B flu viruses are of any real concern for human health, although type C can also cause mild disease in humans ⁽⁴⁾. Type D primarily causes infections in cattle. While type B flu viruses are restricted to humans ⁽⁴⁾, type A flu viruses can also be found in many different animals, including ducks, chickens, pigs, whales, horses, seals and cats ⁽⁷⁾.

Type A flu viruses are the primary cause of annual flu epidemics and all occasional flu pandemics ⁽⁴⁾. There have been five pandemics since 1889, the most severe of which was in 1918 and the most recent of which was in 2009 ⁽⁴⁾.

Flu viruses were first ‘isolated’ in the 1930s, and the first vaccines developed in the 1940s ⁽⁸⁾. In 1960, the US Surgeon General recommended annual flu vaccination for people with chronic debilitating disease, people aged 65 years or older and pregnant women in response to a flu pandemic ⁽⁸⁾.

COVID-19 and the flu: Disease similarities

Signs and symptoms of a SARS-CoV-2 infection include a cough, a fever and shortness of breath. Additional symptoms may include muscle aches, lethargy, runny nose and tiredness ⁽¹⁾. The signs and symptoms of the flu also include a cough, a fever, shortness of breath and muscle aches ⁽¹⁾. The fact that both viruses infect the respiratory tract and show similar symptoms may account for why they are often mistaken for and compared to each other ⁽¹⁾.

COVID-19 and the flu are, however, different.

Sources
(1) https://www.magonlinelibrary.com/doi/full/10.12968/jpar.2020.12.4.136
(2) https://coronavirusexplained.ukri.org/en/article/cad0003/
(3) https://www.reuters.com/article/uk-factcheck-covid-flu-idUSKBN2613BS
(4) https://www.nature.com/articles/s41579-021-00542-7
(5) https://www.sciencedirect.com/science/article/pii/S006535272030021X
(6) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7396141/
(7) https://www.cdc.gov/flu/other/index.html
(8) https://pubmed.ncbi.nlm.nih.gov/33064680/