Study Finds Rise in Severe Neonatal Herpes Infections After Pandemic

HSV-1 has become the dominant subtype among newborns, often not presenting classic symptoms.

Mar. 16, 2026 at 6:39am

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A new study published in Pediatrics suggests that cases of the most severe form of herpes infection in newborns rose significantly following the COVID pandemic. The findings also indicate that herpes simplex virus 1 (HSV-1) has become the dominant subtype among infants with the infection, accounting for 61% of cases.

Why it matters

The shift in HSV epidemiology, with HSV-1 becoming more common in genital infections, may contribute to increased neonatal transmission. Factors like reduced exposure during the pandemic and a growing HSV-naive population of pregnant individuals may have also played a role in the rise of severe neonatal HSV infections.

The details

The study reviewed electronic health records from 632,979 babies born in Northern California between 2008 and 2024. Researchers identified 62 cases of symptomatic HSV infection in infants aged 0-42 days, an overall incidence of 9.8 cases per 100,000 births. While the most common form of infection involved the skin, eyes, or mouth, statistical modeling showed an increase in disseminated infections beginning in 2021, rising from about 1-2 per 100,000 births to about 6-7 per 100,000 by the end of the study period. Many of the symptomatic infants did not present with classical symptoms, with only 21% having fever and 11% having hypothermia, and just over half having visible skin or oral lesions.

  • The study period was from 2008 to 2024.
  • Researchers observed an increase in disseminated HSV infections beginning in 2021.

The players

Tara L. Greenhow, MD

A pediatric infectious disease specialist at Kaiser Permanente Northern California in Oakland, California.

William Schaffner, MD

An infectious disease specialist at Vanderbilt University Medical Center in Nashville, Tennessee.

Betsy Herold, MD

Chief of the Division of Pediatric Infectious Diseases and Vice Chair for Research at Children's Hospital at Montefiore Einstein in Bronx, New York, and a member of the American Academy of Pediatrics Committee on Infectious Diseases.

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What they’re saying

“We see now HSV-1 becoming genital strains causing infection, which may contribute to neonatal transmission.”

— William Schaffner, MD, infectious disease specialist (Medscape)

“Coupled with an increasingly vulnerable HSV naive population, this allowed for many pregnant persons to have primary HSV at delivery.”

— Tara L. Greenhow, MD, pediatric infectious disease specialist (Medscape)

“If the birthing parent only recently acquired HSV, there is insufficient time to develop antibodies. The amount of antibodies that crosses the placenta increases after 33 weeks and exceeds maternal levels after about 37 weeks.”

— Betsy Herold, MD, chief of the Division of Pediatric Infectious Diseases and Vice Chair for Research (Medscape)

What’s next

Researchers and clinicians will need to continue studying trends in neonatal HSV infections and investing in prevention strategies, such as prophylactic vaccines and monoclonal antibodies, to protect infants from this potentially severe infection.

The takeaway

The rise in severe neonatal HSV infections, particularly those caused by the HSV-1 subtype, highlights the need for increased awareness and vigilance among clinicians to ensure prompt evaluation and treatment of infants with atypical symptoms. Addressing underlying factors, such as changes in sexual behavior and exposure patterns, will also be crucial in mitigating this public health concern.