Existence is related to Being. Being is related to Disease. Disease is related to Epidemic. Stress can be Epidemic. 
Detective is a type of Worker. Detective is related to Case. Case is related to Carrier. 
Existence <--RelatedTo--> Being <--RelatedTo--> Disease <--RelatedTo--> Epidemic <--HasProperty-- Stress 
Worker <--IsA-- Detective <--RelatedTo--> Case <--RelatedTo--> Carrier 