Weakened or stressed out fish will die from ick, especially if it invades their gills & causes them respiratory distress (ie. hard time breathing). I found that if fish survive the first ick episodes, their natural immunity will usually protect them from later, lighter infestations.
& Yes, I have also lost several fish to ick, but usually because I wasn't there to treat it right away or did something stupid in the first place. Buying fish from certain LFS will almost guarantee that you get ick
so learn from your's & other's experiences about which place seems to have healthier stock to begin with.
JME
Anthony