Erica J. Sison has dealt with sick and dead dogs and cats, 40 dead lab rats in bags, trophy animals, cooked monkey meat on sticks, human skulls from Indonesia and a live Asian bat that flew out of an airplane cargo hold.

Now she is poised for Ebola, and has seen three false alarms in the last two weeks.

Ms. Sison, the quarantine officer in charge at Newark Liberty International Airport, is on the front lines of a complex system developed to protect United States borders from a “Contagion”-like invasion of rare foreign diseases. It is, she says, a bit anxiety provoking.

“I’ve learned pretty quick that I can never predict what someone is going to tell me when that phone rings,” she said on Friday. “These last two weeks we’ve been on adrenaline.”

The job is a largely unseen and unknown part of the border security system at 18 airports (including Kennedy International Airport) and two border crossings.