Population-based Surveillance of Neonatal Herpes Simplex Virus Infection in Australia, 1997-2011

Background: Neonatal herpes simplex virus (HSV) infection is uncommon, but mortality after disseminated disease and morbidity after encephalitis are high. For the last decade, increased dose and duration of acyclovir has been advised to prevent disease progression and recurrence. We sought to determine prospectively the epidemiologic, clinical, and secular trends of this condition in Australia.

Methods: This was prospective national active surveillance for neonatal HSV disease through the Australian Paediatric Surveillance Unit from 1997 to 2011. Case notification triggered a questionnaire requesting de-identified data from the pediatric clinician.

Results: We identified 131 confirmed cases of neonatal HSV disease in 15 years from 261 notifications (95% response). The reported incidence (3.27 cases per 100 000 live births overall; 95% confidence interval [CI], 2.73-3.86) was stable. Overall mortality was 18.8% (95% CI, 12.1-25.5); the mortality rate was significantly lower in the latter part of the study period, 2005-2011, compared with 1997-2004 (P = .04). There were significantly more young mothers (<20 years of age) compared with Australian birth record data (18.5% vs 4.8%; P < .001). HSV-1 infection was more common than HSV-2 (62.7% vs 37.3%; P < .001), and the rate of HSV-1 infections increased significantly over the surveillance period (P < .05). From 2002, most infants received high-dose acyclovir. The time from symptom onset to initiation of therapy in survivors did not change over time.

Conclusions: Mortality from neonatal HSV infection has fallen but remains high. HSV-1 is the major serotype causing neonatal disease in Australia. Young mothers represent an important target group for prevention.