COVID-19 vs the flu

Photo by Martin Sanchez on Unsplash

One of the most enduring points of disinformation about COVID-19 is that ‘it’s just a flu’ … NO, it’s not.

False information and conspiracy theories about COVID-19 keep comparing the new disease with the seasonal flu (influenza), claiming it’s not more deadly. Such claims are misleading.

The conspiracy theorists have been confidently pushing the ‘it’s just a flu’ lie online largely in response to restrictions placed on movement and the closure of businesses, and the imposition of social / physical distancing measures and lockdowns. These claims are not grounded in evidence and medical science.

To set the scene appropriately, here’s what is known about COVID-19:

  • It’s a new disease that is still being studied, with knowledge about it growing all the time;
  • There is no known cure or vaccine for COVID-19;
  • COVID-19 is caused by the SARS-CoV-2 virus (influenza is caused by a number of viruses).

These basic facts aside, here’s what is known so far about the differences between COVID-19 and seasonal flu (taken from this World Health Organisation (WHO) webpage):

Speed of transmission:

Influenza has a shorter median incubation period (the time from infection to appearance of symptoms) and a shorter serial interval (the time between successive cases) than COVID-19 virus. The serial interval for COVID-19 virus is estimated to be 5-6 days, while for influenza virus, the serial interval is 3 days. This means that influenza can spread faster than COVID-19.

Reproductive number:

The reproductive number – the number of secondary infections generated from one infected individual – is understood to be between 2 and 2.5 for COVID-19 virus, higher than for influenza.

Important drivers:

Children are important drivers of influenza virus transmission in the community. For COVID-19 virus, initial data indicates that children are less affected than adults and that clinical attack rates in the 0-19 age group are low.

Severe and critical infection:

For COVID-19, data to date suggest that 80% of infections are mild or asymptomatic, 15% are severe infection, requiring oxygen and 5% are critical infections, requiring ventilation. These fractions of severe and critical infection would be higher than what is observed for influenza infection.

Most in danger of severe infection:

Those most at risk for severe influenza infection are children, pregnant women, elderly, those with underlying chronic medical conditions and those who are immunosuppressed. For COVID-19, our current understanding is that older age and underlying conditions increase the risk for severe infection.

Death rate:

Mortality for COVID-19 appears higher than for influenza, especially seasonal influenza. While the true mortality of COVID-19 will take some time to fully understand, the data we have so far indicate that the crude mortality ratio (the number of reported deaths divided by the reported cases) is between 3-4%, the infection mortality rate (the number of reported deaths divided by the number of infections) will be lower. For seasonal influenza, mortality is usually well below 0.1%.


On the issue of the death rate, which has especially been singled out by conspiracy theorists and disinformation agents to lie about, in 2019 the WHO stated:

Every year across the globe, there are an estimated 1 billion cases, of which 3 to 5 million are severe cases, resulting in 290 000 to 650 000 influenza-related respiratory deaths.


Consider that as of 1 June 2020, since December 2019 when COVID-19 first appeared in China, there are over 375 000 deaths worldwide. And a study in the US found that the weekly death rate for COVID-19 is nearly 20 times that of the seasonal flu.

Also, according to Johns Hopkins Medicine the following:

COVID-19: There have been approximately 372,479 deaths reported worldwide. In the U.S, 104,383 people have died of COVID-19, as of June 1, 2020. In the U.S., from Oct. 1, 2019 – Apr. 4, 2020, the CDC estimates that 24,000 to 62,000 people died from the flu.

– Johns Hopkins Medicine

And Live Science recently reported:

Researchers from Columbia University recently estimated that only 1 in 12 cases of COVID-19 in the U.S. are documented, which they said would translate to an infection fatality rate of about 0.6%, according to The Washington Post. But even this lower estimate is still at least six times higher than that of the flu. (The case fatality rate in people who become sick with flu may be 0.1%, but when you account for people who become infected with flu but never show symptoms, the death rate will be half or even a quarter of that, the Post reported.)  

– Live Science

For more information on these issues, go to the articles linked to and referenced here, and here and here is some more interesting reading.

What all this is meant to underscore is that COVID-19 is not ‘just a flu’.