Neonatal herpes: case series in two obstetric centres over a 10-year period (2013-2023), France

Neonatal herpes simplex virus (HSV) infection (HSV infection in infants less than 6 weeks of age) is rare but mortality and morbidity rates are high after disseminated disease and encephalitis. In France, the epidemiology is poorly described, and two decades ago, incidence was estimated to be 3 per 100,000 live births a year. We describe determinants, epidemiologic and clinical characteristics of neonatal HSV infection in a managed-care population attending in two major obstetric and paediatric centres, Paris, France, over a 10-year period. This retrospective case series study was conducted from 2013 to 2023, in infants less than 42 days of age who had virologically confirmed HSV infection. We report an overall rate of neonatal herpes of 5.5 per 100,000 live births a year and an incidence of symptomatic cases of 1.2 per 100,000 live births a year. HSV-1 was the major serotype involved (84.2%) and post-natal acquisition through the orolabial route reached 63.2%. All neonates who had neonatal HSV PCR screening (owing to clinical signs in parents) and who received prompt acyclovir treatment remained asymptomatic. Symptomatic forms accounted for 21.1% cases of the total and mortality was high (62.5% of symptomatic forms).   Conclusion: This case series confirms that neonates at risk for HSV disease and poor outcome are those born to HSV-seronegative mothers, preterm infants, and those who received acyclovir after onset of symptoms (mainly because mothers did not present evidence of acute HSV infection). Our study confirms the major role of HSV-1 and the frequency of its early post-natal acquisition. What is known: • Neonatal herpes simplex virus infection is rare but motality and morbidity rates are high after disseminted disease and encephalitis. National recommendations exist worldwide but mangement of this disease is not always easy. What is new: • As in France epidemiology of neonatal herpes is poorly described, our report is potentially an important addition to the existing literature. Moreover, we describe local practice that may be useful to physicians.