You have had a fairly routine day in the pediatric clinic so far: several coughs and colds; a few cases of not-too-serious diarrhea; and an infant with poor weight gain.

You are roused from your desk by the clinic nurse, who asks you to urgently attend to Prisca Cabrini, a 6-hour old baby girl. You introduce yourself to her parents and ask them what the matter is.

"Doctor, Prisca keeps on coughing and bringing up milk whenever I try to feed her. She turned blue when I fed her just a short while ago. I'm really worried." Mrs. Cabrini says.