Anything that triggers the parasympathetic nervous system will tend to cause nausea. Part of the reason is that parasympathetic stimulation tends to cause gastropareisis, or paralysis of the stomach. When it just sits there, with all its contents sloshing around, vomiting is often not far behind.
Infections, fevers, sudden releases of cellular immune modulators into the bloodstream, abnormal sensory input (like dizziness, visual changes), all tend to trigger parasympathetic activity, as does stress and sudden pain.
One hypothesis says the body is wired this way because ingestion of toxins may be responsible for any sudden change in body status; so the body is wired to stop eating, and even purge the stomach contents when system dysfunction arises, as to cease ingesting/expel said toxin. (Said explanation smacks a bit too much of creationism for my taste, but it is an interesting discussion point.)
More could be said on this topic, but not by me at this moment, as I’m feeling just a little queasy.