Herpes Simplex Virus (HSV)

Neonatal herpes simplex virus (HSV) infection, sometimes referred to as “congenital HSV” when acquired in utero, is a serious viral disease that typically presents within the first 6 weeks of life. Transmission is most often peripartum, though a minority, < 5–10%, of cases may represent in utero (congenital) infection with transplacental spread. After exposure, the virus replicates and disseminates manifesting in one of three overlapping syndromes: SEM disease (skin, eye, mouth), CNS disease (encephalitis ± skin findings), or disseminated disease (multi-organ involvement).

The presentation of HSV In lighter‐skinned neonates, those falling into Fitzpatrick I–III and seen in Figures X and XI, often appears as clusters of erythematous vesicles on an inflamed base, sometimes evolving into superficial ulcerations or crusts. In Fitzpatrick types IV–VI and seen in Figure IX, the erythematous base may be muted or appear dusky or hyperpigmented, and the vesicles may blend into background pigmentation, making them harder to appreciate. Since textbook “redness” is less visible, early skin lesions can be subtle or misinterpreted as benign neonatal rashes or other cutaneous skin findings, such as bullous dermatoses. The diagnostic challenge is compounded by the fact that up to ~40% of infected neonates may never develop recognizable skin lesions at presentation. When skin findings are present, it is crucial for them to be appreciated. In case reports and small series, HSV lesions on darker-skinned infants have been misdiagnosed as insect bites or eczema, leading to inappropriate delay in antiviral therapy. 

The treatment for HSV in the infant population, must be prompt and aggressive. Empiric acyclovir is indicated as soon as neonatal HSV is suspected, even before test results confirm the diagnosis. Therapy duration can be upwards of 14-21 days. Following IV therapy, oral acyclovir for approximately 6 months is commonly given to reduce recurrences and improve neurologic outcome. Supportive care and multidisciplinary follow-up is essential.

Since neonatal HSV may present nonspecifically and because skin findings can be subtle, especially in darker skin, clinicians need to maintain a high index of suspicion for any neonate presenting with vesicles, unexplained sepsis, neurologic signs, or hepatic dysfunction. 

1. Kim, D., Lee, J., Park, H., & Cho, Y. (2025). A multicenter study on symptomatic neonatal herpes. Journal of Korean Medical Science, 40, e282. https://doi.org/10.3346/jkms.2025.40.e282

2. Canadian Paediatric Society. (2020). Prevention and management of neonatal herpes simplex virus infections. Canadian Paediatric Society Position Statement. https://cps.ca/en/documents/position/prevention-management-neonatal-herpes-simplex-virus-infections

3. Allen, U. D., Robinson, J. L., & Canadian Paediatric Society, Infectious Diseases and Immunization Committee (2014). Prevention and management of neonatal herpes simplex virus infections. Paediatrics & child health, 19(4), 201–212. https://doi.org/10.1093/pch/19.4.201

4. Johnson, J., Johnson, A.R., Andersen, C.A. et al. Skin Pigmentation Impacts the Clinical Diagnosis of Wound Infection: Imaging of Bacterial Burden to Overcome Diagnostic Limitations. J. Racial and Ethnic Health Disparities 11, 1045–1055 (2024). https://doi.org/10.1007/s40615-023-01584-8