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.