Infection with the influenza virus (flu) varies considerably from year to year, depending on the strain of the virus, the effectiveness of the vaccine and the number of people who have been vaccinated. Currently, the effectiveness of the vaccine is variable and ranges from 40 to 60% depending on the year. But year after year, the influenza virus is a major cause of death worldwide, estimated by the WHO at around 10/100,000 inhabitants. In Quebec more specifically, it is 5.2/100,000, affects between 3 to 7% of adults during a season, and causes 3,500 deaths per year in Canada.

In addition, the influenza virus displays a high rate of genetic mutation, which explains the lack of persistent immunity and the requirement to be revaccinated each year. In fact, due to certain mutations, our immune system no longer recognizes the virus from year to year.

Influenza and SARS-CoV2

Although we currently only have it for the COVID-19 pandemic, the seasonal influenza virus should not be underestimated. Moreover, co-infection with influenza viruses and SARS-CoV-2 (Covid-19) is possible.

The diagnosis of influenza virus as well as that of COVID-19 can only be confirmed by laboratory tests only, but a practitioner can also make a valid diagnosis based on the patient’s signs and symptoms. It is the sudden onset of high fever (≥ 38.5 °), myalgia or arthralgia, headache, severe fatigue, sore throat, or others.

Whether it’s one or the other, Influenza and Covid-19 have a lot in common, such as:

1. They have the same three (3) modes of transmission:

  • Airborne (coughing, sneezing) or by inhaling airborne droplets (the risk via aerosolized microdroplets has not been 100% demonstrated)
  • Direct contact (with secretions from an infected person)
  • Indirect contact (by touching contaminated areas, and knowing that the virus can survive a certain number of hours depending on the porosity of the surface).

2. The same preventive social and health hygiene measures apply in both cases:

  • Wash one’s hands
  • Wear a mask
  • Cough in elbow
  • Physical distancing

3. And finally, the same non-pharmacological measures apply in terms of treatment, namely:

  • Rest
  • Hydration
  • Home care and other containment measures to limit transmission

But are there any distinctive symptoms and signs that could differentiate one from the other? Indeed, the Ordre des Pharmaciens du Québec has drawn up such a list in order to help the professionals concerned with trying to distinguish one from the other. The main differences are in the following symptoms:

Symptoms - Influenza vs Covid

Given the current pandemic situation, it is all the more recommended that everyone be vaccinated for influenza since it is the most effective treatment to prevent influenza. Considering the current congestion in our health system by the pandemic, the relevance of vaccination for influenza is all the more valid as the NNT (Number needed to treat: number of patients to be treated to have a case saved according to the facet considered) of the influenza vaccine in adults is 71 (i.e., with each vaccination of 71 people, we save 1 hospitalization). Who says a decrease in hospitalizations, also means decrease in mortality?


When we think of all the possible complications of the 2 diseases, whether on the nervous, cardiac, respiratory, musculoskeletal system, complications in pregnancy, and even death, it becomes obvious that the population as well as the professionals must take them seriously. And there is at least one of the two diseases for which prevention is possible…

We can therefore never stress enough the relevance that everyone can be vaccinated for the flu, every year, but especially in 2020 and 2021.


André Perreault, Pharmacist




  • Gouvernement du Canada. Maladies et affections. Grippe – Surveillance ÉpiGrippe
  • Boivin, G., Hardy, I., Tellier, G., Maziade, J. (2000). Predicting influenza infections during epidemics with use of a clinical case definition. Clinical infectious diseases, 31(5): 1166-1169
  • Protocole d’immunisation du Québec du MSSS
  • Québec Pharmacie 66(6) :45-61
  • Guide de l’INESS sur la Covid-19
  • Lignes directrices de l’IDSA (Infectious Disease Society of America) – “Clinical Infections Diseases”
  • Formation de l’OPQ (Ordre des Pharmaciens du Québec): « La grippe en pharmacie: le pharmacien à l’écoute de ses patients ».