You and your immunocompromised neighbor both consume undercooked meat containing a pathogenic strain of E. coli. Your neighbor becomes ill (but eventually recovers), whereas you never experience any symptoms. Which of the following is true?

A. Both you and your neighbor had a disease caused by the E. coli pathogen. B. You were never infected with the E. coli strain. C. The E. coli was an ectoparasite in your neighbor, but not on you. D. The E. coli strain ingested was an opportunistic pathogen.