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P1-S1.21 Incidence rate of Herpes Simplex Virus type 2 (HSV-2) in the USA, 1988–2008

Background HSV-2 infection remains a major public health problem in the USA, where the prevalence is 16.2% in persons aged 14–49. In this report, we provide national estimates of new HSV-2 infections in the USA and examine trends in incidence over the past 2 decades. Methods A simple catalytic model was used to estimate HSV-2 force of infection (FOI), defined as the incidence of HSV-2 in the susceptible population, from National Health and Nutrition Examination Surveys (NHANES) in the USA from 1988 to 2008. HSV-2 serology was included in the nationally representative surveys during 1988–1994 (NHANES III) and in continuous NHANES from 1999 to 2008. Incidence rates and trends over time were estimated by age, sex and race/ethnic group for non-Hispanic whites, non-Hispanic blacks, and Mexican-Americans. Results HSV-2 FOI rates were highest in non-Hispanic blacks and lowest in non-Hispanic whites, with the FOI among 25-year-old non-Hispanic black women more than 13 times greater than white men of the same age. Rates were highest between ages 25 and 35 years for all sex-race/ethnicity groups (peak in non-Hispanic white and black women aged 25 years, in non-Hispanic white and black men aged 35 years and in Mexican-American women in their early-30s) except for Mexican-American men, for whom there was less variation in FOI by age. Over the last 20 years, age-adjusted FOI rates were stable for the sex-race/ethnicity groups examined except for non-Hispanic white and Mexican-American women, in which there were decreases after 2002 and 2001, respectively. FOI rates were lower in men than women among non-Hispanic blacks and Mexican-Americans, and in non-Hispanic whites prior to 2002. Overall, the estimated number of new HSV-2 infections in 2007–2008, among these three groups, aged 14–49 years, was in excess of 750 000, with 48% (∼360 000) occurring in women and 52% (∼392 000) in men. Nearly half (45%) of all infections occurred in persons under 25 years old (34% and 57% of infections in men and women, respectively). Conclusion Risk of HSV-2 infection varies substantially across the US adult population, with the highest risk among non-Hispanic black men and women. Information on the detailed distribution of new infections can help improve the efficiency of interventions. In addition, although we found evidence for substantial reductions in the risk of HSV-2 among some race/ethnicity groups, FOI in groups with the highest rates has not changed in 20 years.