Herpes simplex infection in children — branching viva

Opening question

Examiner: Take me through this infant. What is the diagnosis, and what is your frame for managing him? ^[2]

Candidate: The leading diagnosis is neonatal herpes simplex virus disease. A 12-day-old with fever, poor feeding and lethargy has bacterial sepsis on the differential, but this infant has the highest-risk HSV exposure: a maternal primary genital HSV at 38 weeks with vaginal delivery through active lesions, because a primary infection means the mother has not yet made antibody to transfer to the baby. The scalp vesicle clinches it. My frame is to treat this as neonatal HSV from the first minute — start high-dose intravenous aciclovir, run the full HSV workup, and treat empirically because outcome worsens with every hour of delay. ^{[2] [7]}

Examiner: Why is a primary maternal infection so much more dangerous than a recurrent one? ^[1]

Candidate: Because neonatal HSV transmission is far higher from a primary genital infection — around forty-four percent — than from a recurrent one, which is only a few percent. In a primary infection the mother lacks antibody, so the neonate receives neither transplacental antibody nor the cell-mediated advantage of maternal immunity. The baby meets a large viral inoculum unprotected, and the immature neonatal immune system cannot contain it. ^{[1] [7]}