What is the difference between infected and infectious in epidemiology?
(The document you link to says "see Chap. 1 for distinction between infected and infectious individuals", but I'll assume you don't have access to that - I certainly don't.)

Infected individuals have been infected by a pathogen.
Infectious individuals have the potential to transmit a pathogen to 
others.

Note that the definition given for "infected" in the source you link to is actually wrong: hosts may have a subclinical infection, in which case they are not "now sick with it".