How long does a flu/cold virus linger in a body after the symptoms subside?

Does the body kill them all within a week or so, or do they linger for quite awhile afterwards while inducing no physical symptoms?

At least some of the flu symptoms we feel are a result of our immune system fighting the attack, however we don’t have to wipe out every single virus in order to feel better and no longer be contagious.

I suspect that some virus particles survive for quite a long time after we get better because there are no longer enough of them to make us sick or to trigger a massive immune response.

Don’t know if this is factual enough for GQ, but when I had H1N1 around an un-vaccinated pregnant coworker, my doctor told me to either stay home or wear a mask at work during symptoms and for 48 hours after symptoms subsided. I stayed home for two days and wore a mask for 2 days. No one else got sick with it.