I’m assuming you are asking “How was Jenkins exposed to Ebola”?
My understanding was he spent 30 minutes unprotected in the apt shortly after Duncan was diagnosed with Ebola. He also claimed he gave the family the ride over to the secret place. If the family et al does not have Ebola, which it is looking like is the case, then he wasn’t “exposed” to it. Just sheer negligence on his part to take that risk, and then to go home to his family, to his job, etc.
Ebola can live outside the body on surfaces for around 12 hours. If he went into the apartment more than 12 hours after Duncan left, he would not have been exposed.