Colloquially people talk about the flu as if its like a cold but a little worse. But the flu can be very serious: https://www.cdc.gov/flu/symptoms/symptoms.htm

Fevers of 5+ degrees F (lasting 3-5 days), chills, aches, chest pain, etc. And complications (eg pneumonia) are fairly common and can be deadly.

I would wager that most "flu" cases people self-report aren't actually the flu.

People that talk this way about the flu most likely have not had the flu, or at least not a “full flu”. I came down with it in a year when the flu shot was particularly ineffective and that was enough to end any deliberation with the flu shot for me ever again.

How about paralysis?

https://www.cdc.gov/vaccinesafety/concerns/guillain-barre-sy...

Not directly caused by the flu but correlated, fortunately quite rare.

Interesting. I has heard the link between GBS and the flu vaccination before (since all the flu vaccine questionnaires mention it), but that article suggests there's evidence that the flu is more likely to cause it than the vaccination, which is supported by this article:

https://www.ncbi.nlm.nih.gov/pubmed/19025491

"the flu", i.e. influenza, is definitely not "you have a sniffle, get over it"

more like feeling like you've been hit by a truck for 2 weeks while you shiver in bed with a fever, coughing your lungs out, unable to function

That was always my impression of the flu, until this year. My husband, infant daughter, and myself all came down with the flu within 3 days of each other. The infant had been vaccinated, while my husband and I were not. The infant and husband were confirmed via a nose swab to have the flu, while we just inferred that I got it since we all had classic flu symptoms.

Despite not being vaccinated, my husband was feeling 80% better within three days and fully recovered within four days. He was miserable for the first two days, but still not the level of ‘got hit by a truck’ that I remember from previous cases. I took five days to recover and also had relatively mild symptoms - it was undeniably different from a common cold (muscle soreness, chills and night sweats, fatigue) but I wouldn’t have thought it was the flu if the rest of my family wasn’t infected. My daughter seemed to be recovered within 48 hours, though she later contracted pneumonia. Even that was managed within 24 hours of starting amoxicillin and a nebulizer.

This post has gotten pretty long, but my point is that, for whatever reason, we came down with a flu that wasn’t nearly as bad as the norm. Even the doctors were skeptical until the test results came back.

And you may not 'feel better again' for a month, or two, or more.

My anecdata from a few influenza events is that it is truly awful. A week of slowly worsening fever. I got close to admitting myself to hospital before my fever broke and I recovered. Symptoms dissapear very quickly once it's over, but it took me months to recover my fitness.

Some people may have only mild fever and some are even asymptomatic.

As others have alluded to, I think you are confusing flu with cold.

I agree with the others, but I think we should note that these sorts of illness are not divided neatly into two categories, cold and flu. Besides the many different viruses grouped under "the common cold", there is a whole spectrum of bacterial infections whose symptoms look similar to, and interpolate between, the cold and flu. So there are other things someone could get that are like less severe version of the flu, but are worse than a common cold, and it's hard to distinguish without a formal test.

I believe pneumonia can be caused by a number of bacteria. These used to be very deadly before the advance of antibiotics, much worse than the flu or cold.

Influenza is a serious disease that kills tens of thousands of people every year.

https://www.cdc.gov/flu/about/burden/index.html

The overwhelming majority of deaths are elderly people though. Then most of the rest are above middle aged. Only a tiny percentage of young healthy people die from the flu. One thing that's very different about some of these strains.

EDIT: not to minimize the flu though. Comparing a flu to a cold is like comparing a migraine to a tension headache.

The flu can be very serious.