Is it unusual for symptoms of a virus to vary this much?

[CrumpledCrumpet]

One thing that has struck me about covid is that the type and severity of symptoms that people experience are so very different.

Is it usual for viruses to do this? I mean everyone always says “if you’ve got the flu you’ll know about it, you won’t be able to get out of bed!”. Is that actually true or can you have asymptomatic/mild flu too?

Do other viruses cause gastric symptoms in some people but cold-like symptoms in another?

Basically, is covid really unusual or do other viruses have similarly varied effects?

I think they're varied but we never talk so much about one virus.

It's not the virus it's our immunity systems - which are all very varied.

I guess ordinarily we don't know we've got the same virus as we don't test. You and I could assume we have the same cold and remark that your symptoms are more severe / different to mine but we wouldn't definitely know it was the same virus.