Explaining neonatal HSV and the exposed-neonate pathway — OSCE

Candidate instructions (8-minute station)

You are the paediatric registrar in the postnatal ward. A mother developed a first episode of genital herpes at 38 weeks gestation and delivered vaginally 18 hours ago. Her baby boy is currently well — feeding, afebrile, no rash — but is recognised as a high-risk HSV exposure because this was a primary maternal infection near delivery. The parents are anxious and confused: the mother had never had genital herpes before, the baby looks perfectly well, and they cannot understand why the team is talking about tests, isolation and possibly an antiviral drip. [7]

Your tasks are: [2]

1. Explain in plain language why a primary maternal genital HSV near delivery is a high-risk exposure for the baby, and why the baby needs close observation, surface swabs and a low threshold for treatment. [1] [7]
2. Explain what neonatal HSV is, its three disease classes, and why the team would start an antiviral (aciclovir) promptly if the baby became unwell — including that early treatment changes the outcome. [2]
3. Address the parents' worry that the team is "over-treating" a well baby, and set out what the parents should watch for at home after discharge. [7]
4. Explain how a future pregnancy would be protected — suppressive aciclovir and caesarean delivery. [1] [5]

You are not expected to give exact aciclovir doses to the parents; explain the plan in plain language and flag that any decision to start treatment is made by the neonatal team with the parents' consent. [2]

Examiner prompt to the actor (father)

"She's never had this before — we've been together for years — so where has it come from? And the baby's absolutely fine, he's feeding, he's perfect. Why are you talking about an infection and a drip and keeping him in? Surely if he was going to be sick he'd be sick by now? And are you saying she'll have this forever?" [7]

Marking domains

• Frame and explanation (3): explains in plain, non-judgemental language that a first-ever genital herpes near delivery is the highest-risk scenario because the mother's body has not yet made protective antibody to pass to the baby; names that the baby may have met the virus during the birth without showing it yet; sets the expectation that the baby is well now but is being watched and tested precisely because the signs can take days to appear. [1] [7]
• Neonatal HSV and the treatment rationale (3): explains what neonatal HSV is and its three forms (skin-eye-mouth, the brain, and widespread or disseminated disease); explains that the team would start an antiviral drip (aciclovir) promptly if the baby became unwell because early treatment changes the outcome and prevents long-term harm to the brain; acknowledges that a well-appearing baby does not need the drip immediately but does need the swabs and the watch. [2] [5]
• Reassurance and safety-net (2): addresses the father's confusion without defensiveness, avoids blame or speculation about the source of the infection, and gives a clear safety-net — fever, poor feeding, lethargy, a rash or blisters, or anything "not right" means returning immediately. [7]
• Future pregnancy prevention (2): explains that suppressive antiviral tablets from late pregnancy and a caesarean if there are active lesions at delivery dramatically reduce the risk for a future baby, and that the team and the obstetric service will plan this together. [1] [5]

Model answer — the explanatory script

"Thank you for coming in, and I can see how worrying this is, especially when your son looks so well. Let me explain what's happening and why we're being careful, because the two things are connected." [7]

"First, the herpes simplex virus. It's a very common virus — most adults carry it. It can appear as a cold sore, or, as in your partner's case, as a genital sore. When someone has it for the first time, their body hasn't yet made the antibodies — the natural defence — to pass on. Because your partner's first episode happened so close to the birth, your son met the virus during the delivery, and because it was her first infection, he didn't get those protective antibodies from her. That's why, even though he looks well now, he's what we call a high-risk exposure. We're not saying he's infected — we're saying he met the virus, and we want to watch him and do some swabs to be sure." [1] [7]

"Now, what is neonatal herpes? It's when the virus affects a newborn in one of three ways. The mildest is on the skin, in the eye or in the mouth — blisters or a sore. The more serious is in the brain, which can cause drowsiness, poor feeding or fits. And the most serious is when it spreads through the body — what we call disseminated disease. The really important point is this: if a baby does start to show signs, starting an antiviral medicine called aciclovir through a drip early — straight away — makes a huge difference to the outcome. It can prevent long-term harm to the brain. That's why we have a low threshold to start it. Your son is well now, so he doesn't need the drip this minute, but he does need the swabs and close watching, and if anything changes we start the medicine promptly." [2] [5]

"I can hear your worry that we're over-treating a perfectly well baby, and that's a fair thing to ask. The truth is the signs of neonatal herpes can take a few days to appear — the baby can look entirely well and then become unwell. So we watch for the warning signs: a fever, not feeding well, being sleepier or floppier than usual, a rash or little blisters, or just anything that isn't right. While you're here, we check him regularly; when you go home, those are the signs to bring him straight back for. We'd rather watch a hundred well babies closely than miss one who becomes unwell." [7]

"And for a future pregnancy — because I know you'll be thinking about this — there is a clear pathway to protect the next baby. If your partner takes an antiviral tablet from about 36 weeks of pregnancy, it suppresses the virus and reduces the chance of a sore at delivery. And if there is a sore when labour starts, we'd recommend a caesarean so the baby doesn't pass through the virus. Together those two things dramatically lower the risk. Your obstetric team will plan all of this with you for next time." [1] [5]