you would Study because Interested. Study is related to Literature. Literature can be used for Learning. you would Learning because Growth. 
Infection is a type of Disease. Infection is a type of Illness. 
Interested <--MotivatedByGoal-- Study <--RelatedTo--> Literature --UsedFor--> Learning --MotivatedByGoal--> Growth 
Disease <--IsA-- Infection --IsA--> Illness 