Herpes or Bacterial Infection? Testing and Treating Young Infants

William T. Basco, Jr., MD, MS


July 12, 2018

Evaluating Infants for Herpes Infection

It can be difficult to identify young infants with herpes simplex virus (HSV) infection of the central nervous system (CNS), given that the symptoms often mimic those of bacterial infection.[1] Therefore, young symptomatic infants are often evaluated for both HSV and bacterial CNS infection and started on empiric therapy while awaiting results of testing.

To assess this approach, a recent study[1] sought to determine the frequency of HSV infection in infants evaluated for CNS infections in emergency departments (EDs). The data were drawn from 23 pediatric EDs in the United States and Canada. Children younger than 2 months who were treated in the ED at one of the participating facilities from 2005 through 2013 were identified, focusing on those from whom cerebrospinal fluid (CSF) bacterial cultures were obtained. Clinical data collected through chart review included demographic data, vital signs, types of testing done, and whether the children received empiric antiviral therapy. The main outcome of interest was the proportion of ED encounters in which HSV infection was confirmed through polymerase chain reaction (PCR) testing or viral culture of CSF, blood, mucosa/skin surfaces, or other body fluids.

Study Findings

Approximately 35% of all children from whom CNS bacterial cultures were taken in the ED also underwent HSV testing by PCR (33.6% using CSF and 4.5% using blood). Empiric treatment with acyclovir was administered to 23.4% of all children tested for HSV infection in the ED, and 90.8% were admitted to the hospital. Ultimately, 112 children were diagnosed with HSV infection (0.42%; 95% confidence interval, 0.35% - 0.51%). Thus, HSV infection was identified in 1.2% of the children who were tested for HSV, and was almost equally distributed between skin-eye-mouth, CNS, and disseminated disease. The peak incidence of HSV infection was during the second week of life, and only 0.17% of the children aged 29-60 days at the time of evaluation had HSV infection.

The number needed to treat (NNT) empirically with acyclovir to treat one true case of HSV infection was 237 infants. However, among children who were tested for HSV, the NNT was 82. The investigators concluded that 0.42% of children aged ? 60 days who were tested with CSF culture had HSV infection, peaking in the second week of life.


It's always helpful for clinical decision-making to see updated epidemiologic data, especially when it comes from such a wide representation of the United States and Canada. The data suggest that the most important window of HSV identification is the first 28 days of life, but cases will still be identified in the 9- 12-week age range. The NNT of 82 among those tested for HSV doesn't seem too unreasonable, given the potential lethality of HSV infection. However, as the investigators suggest, it would be desirable to obtain additional clinical research data to help us refine evaluation to a smaller group of young infants.


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