system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do colds/flu/bugs seem to end with an annoying cough that lasts for ages?
gpt
This is partially due to the fact the airways are still irritated from the effects of the illness, and partially because the flu weakens the immune system and allows additional infections.

It is, in fact, relatively common for more vulnerable people to develop bronchitis or pneumonia after a flu. This is why almost every source you ask about flu symptoms will tell you to see a doctor if your cough lasts too long, or if your fever disappears for a day or two and then comes back.