Background:
Neonatal herpes infection is not common but the consequences of the infection can be severe. The incidence of neonatal herpes is not well known and it has been suggested that it be a reportable disease.

Objective:
Using a readily available data source, estimate the incidence and trends of neonatal herpes and determine the cesarean section rate in delivering mothers with a discharge diagnosis of herpes.

Method:
California Hospital Discharge Dataset were used for the years 1995 to 2003. ICD 9 codes for herpes (054.1-054.9) were used to identify potential cases. Neonatal cases were defined as an age of 42 days or less at the date of admission. ICD 9 codes at discharge were used to identify mothers giving birth (V27) and whether they had cesarean section (procedural code 74).

Result:
The number and incidence rates of neonatal HSV were generally stable from 1995 to 2003 with approximately 60 cases per year and an overall rate of 12.2 per 100,000 live births. In 1995 and 2003 the rates were 11.1 and 10.7 per 100,000 live births, respectively. Rates of neonatal herpes differed by race/ethnicity with a range from 6.2 per 100,000 live births in Asian Pacific Islanders to 17.4 per 100,000 in African Americans. The cesarean section rate declined from 64% in 1995 to 55% in 2003 in mothers with a discharge diagnosis of herpes compared to a rise in the overall cesarean section rate from 21% to 28% for that time period.

Conclusion:
Hospital discharge data may be a readily available data source to monitor neonatal herpes rates but it needs validation. Using hospital discharge data neonatal herpes rates in California did not change significantly between 1995 and 2003.

Implications:
Hospital discharge data may be a promising cost efficient alternative to case-based reporting for neonatal herpes, however the sensitivity of this methodology is uncertain.