How the flu compares to COVID-19

Medical Watch

As we enter influenza season this fall, how can you tell the difference? Add the common cold to the equation and it’s a formula for confusion. We asked Dr. Khalilah Gates, a Northwestern Medicine pulmonary and critical care doctor to break it all down.

Do symptoms of the flu and COVID-19 overlap?

Gates: The common symptoms of both COVID-19 as well as influenza are fevers, cough, body aches, muscle pains, and so we will definitely have to take a very good history to try to distinguish between the two, but, more than likely, if a patient is to present with those symptoms, they will have a COVID swab as well as a flu swab.

Is fever a deciding factor?

Gates: Right now, there is no clear difference between a covid-19 fever and the flu fever. Just like flu we have majority of the patients who at some point have a fever, but there are patients who have no fever or very low grade. So, there is nothing about the fever itself to my knowledge that can distinguish covid from influenza this year.

Is cough a clue?

Gates: The major presentation for COVID-19 is cough. It’s typically a dry cough, not a lot of mucus production. Cough is not as much of a presentation for flu, although it can be there with flu as well. But, again, there are no clear distinctions with the quality of cough that would have us say this is COVID vs. influenza.

Symptoms: Rapid vs. slow onset?

Gates: Actually, flu symptoms are typically more rapid. So, you get exposed, you are pretty sick pretty quickly. People often describe flu as they were feeling well and then, all of a sudden, they felt like they got hit by a truck or a ton of bricks, whereas covid seems to be this more gradual, progressive build-up of symptoms.

The common cold

Gates: Typically, the symptoms are very mild, so runny nose, sneezing, sore throat is typically not associated with fevers and not associated with those body aches, so a little bit of a different presentation. So, I think the key factor is not trying to differentiate it yourself. If you are having symptoms, that’s fever, shortness of breath, cough, you contact the healthcare provider, contact the various covid hotlines at your nearest hospitals, and allow those people to help guide you through what the next steps are.

It’s possible to get the flu and COVID-19 at the same time — about 10% of patients had co-infections at the start of the pandemic last February and March, when it crossed over with flu season. If you do get sick with both, you may have a more severe illness and require closer monitoring. Bottom line, doctors say get your flu shot — it won’t help protect against COVID-19 — but it can help lessen the severity and length of influenza.

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