Just remember, effect is a result (remember the 'E' in result) and affect is an action (rememeber the 'A' in action).
If something has an effect, it affects things.
EXAMPLES: Bob's infection had an effect on his wife. Bob's infection affected his wife. Bob's wife knew the fact that the infection was from an infestation. Bob's wife was, in fact, infected yourself. He faxed the fact that she was infected to her and the effect affected her.
FYI, infect is something you get from from 'punching the midget' just after you clean fish.