Objective To estimate the incidence of neonatal herpes simplex virus (HSV) infection and the number of neonates with suspected invasive bacterial infection (IBI) needed to treat (NNT) with acyclovir to ensure prompt treatment of invasive HSV infections.
Design A nationwide population-based cohort study.
Setting All neonatal and paediatric emergency departments in Denmark from 1 January 2010 to 31 December 2019.
Patients Neonates aged 0–28 days with HSV infection.
Main outcome measures The main outcome measures were incidence and NNT. The NNT was calculated based on neonates with invasive HSV infection whose onset symptoms resembled IBI and the estimated number of Danish neonates who received antibiotics for suspected IBI.
Results Fifty-four neonates with HSV infection were identified, that is, an incidence of 9 per 100 000 live births. Twenty presented with symptoms resembling IBI, all within the first 14 days of life. Of 18 (78%) neonates, 14 had elevated C reactive protein, 14 of 19 (74%) had elevated alanine aminotransferase and 11 of 17 (65%) had thrombocytopaenia. The estimated NNTs with empiric acyclovir at postnatal ages 0–3, 4–7 and 8–14 days were 1139 (95% CI 523 to 3103), 168 (95% CI 101 to 726) and 117 (95% CI 48 to 198), respectively.
Conclusions The incidence of neonatal HSV infection was higher than in previous decades; however, the estimated NNT with empiric acyclovir was high. Therefore, we propose not to treat all neonates suspected of IBI with empiric acyclovir, as current European guidelines suggest. However, HSV should be considered in neonates with signs of infection, especially after the third postnatal day and in neonates with high alanine aminotransferases and thrombocytopaenia.
- infectious disease medicine
Data availability statement
Data are available upon reasonable request.
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Contributors KHSD, UN and TBH conceptualised and designed the study, collected the data, performed data analyses and interpretation, drafted the initial manuscript, and critically reviewed and revised the manuscript. SL, ELMC, UBH and ATM helped conceptualise the study, interpreted the data, and critically reviewed and revised the manuscript. KTF, MKT, HLN, ACYN and USJ helped collect data, conceptualised the study, interpreted the data, and critically reviewed and revised the manuscript. All authors approved the final manuscript and agree to be accountable for all aspects of the work. Guarantor is KHSD.
Funding This work was supported by the Innovation Fund Denmark (grant number 0176–00020B).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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