Nikhil Prasad Fact checked by:Thailand Medical News Team Sep 04, 2026 35 minutes ago
A worrying rise in the most dangerous form of herpes simplex virus (HSV) infection among newborn babies has emerged following the COVID-19 pandemic, according to a large 16-year study from Northern California. Researchers found that disseminated HSV, in which infection spreads through the body and can affect multiple organs, increased sharply after 2021.
A major study found a sharp post-pandemic rise in dangerous disseminated herpes infections among newborns,
often without classic warning signs.
The researchers were from the Division of Infectious Diseases, Department of Pediatrics, Kaiser Permanente Northern California, San Francisco, California.
HSV-1 Now Dominates Newborn Infections
Researchers reviewed electronic health records covering 632,979 infants born between October 2008 and September 2024. They identified 62 babies aged 0 to 42 days with symptomatic HSV, producing an overall incidence of 9.8 cases per 100,000 births.
Importantly, HSV-1 was responsible for 61 percent of infections, while HSV-2 accounted for 32 percent, with the remaining cases having an unknown subtype. HSV-1 was historically associated mainly with oral herpes, but it can also cause genital infections that may be transmitted to babies around delivery.
This
Thailand Medical News report highlights an especially concerning change in disseminated disease. While skin, eye, and mouth infections and central nervous system infections remained relatively stable, disseminated HSV began increasing significantly in 2021. Researchers calculated an increase of 4.5 cases per 100,000 births per year from 2021 through 2024.
Many Infected Babies Had No Classic Warning Signs
One of the study's most important findings was how easily neonatal HSV could potentially be overlooked.
Among symptomatic babies with detailed clinical information, only 21 percent developed fever and just 11 percent experienced hypothermia, or abnormally low body temperature. Slightly more than half had visible skin or mouth lesions. About one-third appeared seriously unwell, with possible symptoms including lethargy, poor feeding, breathing difficulties, or signs resembling sepsis.
Researchers calculated that restricting HSV evaluations to newborns with abnormal temperatures would have missed 68 percent of cases.
Most infections appeared during the first two weeks after birth. Premature infants were particularly vulnerable, with an incidence of 28.3 cases per 100,000 births compared with 8.1 per 100,000 among full-term infants.
Severe Disease Carried a High Risk of Death
The consequences were dramatically different depending on how extensively HSV had spread. Six infants died during the study. There were no deaths among babies whose disease was restricted to the skin, eyes, or mouth.
However, 28 percent of infants with disseminated H
SV died, as did 10 percent of babies with central nervous system disease.
Testing also declined over the study period, dropping from approximately 895 tests per 100,000 births in 2011 to around 595 per 100,000 in 2021. Once HSV was suspected, however, antiviral treatment was generally started on the same day testing was performed.
Why Cases May Have Increased
Researchers suggested that pandemic-era changes in HSV exposure and sexual behavior may have left more people without existing HSV antibodies before pregnancy, potentially increasing the likelihood of primary infection around delivery. However, this explanation remains a hypothesis, and researchers stressed that longer surveillance is required.
Conclusions
The findings show that neonatal HSV remains uncommon but can become rapidly life-threatening, particularly when infection spreads throughout the body. The sharp post-pandemic rise in disseminated disease, combined with the frequent absence of fever or obvious lesions, underscores why clinicians may need to consider HSV even when newborns do not display its classic warning signs.
The study findings were published in the peer reviewed journal: Pediatrics.
https://publications.aap.org/pediatrics/article/157/4/e2025073629/206758/Epidemiology-of-Herpes-Simplex-Virus-in-Infants
Read Also:
https://www.thailandmedical.news/articles/coronavirus
https://www.thailandmedical.news/articles/long-covid
Share
Tweet
Share
