Infant HSV Occurs Much Later Than We Thought

Spoon Feed
HSV was rare in infants under 60 days, <1%.  However, 9% occurred in weeks 5-6 and 11% in weeks 7-9, which was a much later onset than previously thought.

Why does this matter?
HSV infection in infants presents as either disseminated disease, skin/eye/mouth (SEM) disease, or CNS disease.  Based on a prior study, we understood that, on average, disseminated and SEM presented by day 10-11; CNS disease by day 17, out to day 35.  Many, like CHOP, consider HSV testing out to day 40 to be cautious.  This study examined the presence of HSV disease in infants under 60 days and found reason for concern if testing is halted at day 40.

HSV in Infants
This was a retrospective study of infants under 60 days who had undergone HSV testing by PCR or viral culture including CSF at 1 of 23 centers in N. America.  Out of 26,533 encounters, 112 infants (0.42%) had confirmed HSV disease of some kind.  80% occurred in weeks 1-4; 9% in weeks 5-6; 11% in weeks 7-9.  Over half (68/112) had disseminated or CNS disease.  One take-home from this study is that HSV occurred later than we previously thought.

The study is limited because empiric testing and treatment for HSV was widely variable across sites, 34% and 23%, respectively.  But overall, the prevalence of HSV in infants under 60 days was quite low.  The authors noted, "the number needed to treat with empirical acyclovir to ensure all cases of HSV were treated initially for potential infection was 237."  Empiric treatment with acyclovir is known to be associated with increased cost, increased length of stay, and possible adverse effects such as nephrotoxicity, myelosuppression, or electrolyte abnormalities.  The other take-home point from this article is that empiric treatment is not an easy decision.  For example, CHOP will start acyclovir if: </= 21 days, or 22-40 days and ill-appearing, abnormal neurologic status, seizure, vesicular rash, hepatitis, or mother known to have primary HSV infection at delivery.  This seems like a reasonable approach, but institutional protocols like this will need to reconsider stretching this beyond 40 days in light of this new information.

Another Spoonful
EM Lit of Note did an excellent summary of this article.

Source
Herpes Simplex Virus Infection in Infants Undergoing Meningitis Evaluation. Pediatrics. 2018 Jan 3. pii: e20171688. doi: 10.1542/peds.2017-1688. [Epub ahead of print]

Peer reviewed by Thomas Davis, MD.

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