Dark is related to Very. Very is related to Honest. Honest is related to Direct. Direct is the opposite of Shade. 
Infection is related to Disease. Abortion is a type of Disease. 
Dark <--RelatedTo--> Very <--RelatedTo--> Honest <--RelatedTo--> Direct <--Antonym--> Shade 
Infection <--RelatedTo--> Disease <--IsA-- Abortion 