A 56% increase in neonatal herpes simplex virus (HSV) infection over 7 years was determined as part of a retrospective, multistate, longitudinal cohort study using information collected from the MarketScan Medicaid Database, reported Sanjay Mahant, MD, of the University of Toronto, and his associates.

Comprehensive coordinated care – as well as public health strategies targeting disease prevention, early diagnosis, and treatment – are needed to manage the growing number of neonates diagnosed with HSV, Dr. Mahant and his colleagues said.

A total of 900 newborn Medicaid enrollees aged 0-28 days were chosen from 2,107,124 births for inclusion in the study. All patients, who were diagnosed with HSV infection during hospital admission, were born during Jan. 1, 2009–Dec. 31, 2015.

Susceptibility to primary HSV-1 infection among younger women has been attributed to an increase in oral sex practices over the past 2 decades, which is putting adolescents and young adults at greater risk of genital HSV-1 infection (J Infect Dis. 2007;196[12]:1852-9). As a result, more “primary or nonprimary genital HSV-1 infections among childbearing women” are believed to be the likely cause for the increasing numbers of neonatal HSV cases, the authors speculated, citing a recent study (J Infect Dis. 2014 Feb 1;209[3]:315-7).

HSV, a rare infection typically contracted immediately before or after birth, has both high morbidity and mortality rates; transmission rates “after exposure and during delivery increase from 2% in recurrent infection to 25% and 60% in nonprimary and primary infections, respectively,” Dr. Mahant and his colleagues noted.

Over the study period, disease incidence grew from 3.4/10,000 births in 2009 (1/2,941 births) to 5.3/10,000 births in 2015 (1/1,886 births).

Dr. Mahant and his associates noted several limitations in the study that might explain the increase in incidence.

ICD diagnosis codes, which they characterized as imperfect in their ability to correctly identify neonatal HSV infections, may have led researchers to include infants who were not actually infected or (less likely) to have excluded infants who were infected. States participating in the MarketScan Medicaid Database also may have changed over the study period. Incomplete follow-up after hospitalization made it impossible to track infants who had changed insurers, moved to other states, or died during the study. They also cautioned that outcomes may not be transferable to the general population because outcomes were specific to Medicaid enrollees.

The total cost for initial hospitalization and treatments provided during 6 months of follow-up was $60,620,431 ($87,602 median cost per patient) for the cohort of 900 infants. This is significant given that the authors reported a median length of stay of 18 days for initial hospitalization. Of the 846 patients discharged (54, or 6%, died during initial hospitalization), follow-up data was available for 692 (81%). A total of 316 (46%) infants required at least one subsequent visit to the emergency room, and another 112 (16%) experienced at least one hospital readmission.

That Dr. Mahant and his colleagues “observed high health care use and associated payments over the first 6 months, including and after hospitalization for neonatal HSV” suggests that there is a need for comprehensive, coordinated care once neonatal patients receive a diagnosis of HSV.

“Public health strategies that are targeted on disease prevention and early diagnosis and treatment are needed,” they advised.

The authors had no relevant financial disclosures. The study was funded by the National Institutes of Health.

SOURCE: Mahant S et al. Pediatrics. 2019 Mar. doi: 10.1542/peds.2018-3233.