Chapter 55: Herpes Simplex Virus

INTRODUCTION

Neonatal herpes simplex virus (HSV) infection refers to any HSV infection occurring in infants within the first 28 days of life. Most infants present with symptoms within the first 2–3 weeks of life, and some cases are recognized as late as 4–6 weeks of age (rare cases recognized up until 8 weeks of age). Both HSV-1 and HSV-2 cause serious infection in the neonate. If infection is unrecognized and untreated, 50% of infants with central nervous system (CNS) HSV disease and 85% of infants with disseminated HSV infection die by 1 year of age.¹ Advances in the diagnosis and treatment of neonatal HSV infection since the mid-1980s have improved the outcomes of infected infants.² Despite advances in care, there is no evidence that the incidence of infection has decreased. Delay in diagnosis persists, and some infants who survive infection suffer devastating long-term sequelae.²

EPIDEMIOLOGY

Neonatal HSV infection is an uncommon disease, but early recognition and treatment are crucial in preventing mortality and long-term morbidity. Most neonatal HSV infections are in infants born to mothers with genital HSV-1 or HSV-2 infection. The remaining cases occur in infants exposed shortly after birth to a family member or health care worker with mouth or skin HSV-1 lesions. Based on serologic data from the National Health and Nutrition Examination Survey (NHANES), it is estimated that 22% of pregnant women in the United States are HSV-2 positive, 63% are HSV-1 positive, and 13% are seropositive for both viruses.³ Non-Hispanic white women were more likely to be seronegative for HSV compared to other racial and ethnic groups. HSV-2 causes most cases of genital herpes in the United States; however, genital infections with HSV-1 are increasing, and recent studies suggested that HSV-1 has now surpassed HSV-2 as a cause of genital herpes in college-age individuals.⁴ Women infected with HSV-2 are more likely to have recurrent symptomatic and asymptomatic shedding of virus compared to those with HSV-1.⁵

Most persons (70%–80%) with genital HSV have no symptoms; therefore, a history of no lesions during pregnancy does not rule out risk for neonatal HSV infection (Table 55-1). Some women with primary infection or recurrent disease have only nonspecific symptoms, such as fever or genital burning with urination that is mistaken for a urinary tract infection. Recurrence of genital herpes during pregnancy is common. Asymptomatic reactivation of genital HSV associated with short episodes of viral shedding and rapid clearance of virus likely occurs more frequently than previously thought.⁶