Herpes simplex virus type 1 (HSV-1) and type 2 are common infections worldwide. Herpes
simplex virus type 2 (HSV-2) is the cause of most genital herpes and is almost always
sexually transmitted. In contrast, HSV-1 is usually transmitted during childhood via
nonsexual contacts. Preexisting HSV-1 antibodies can alleviate clinical manifestations
of subsequently acquired HSV-2. Furthermore, HSV-1 has become an important cause of
genital herpes in some developed countries.
To examine trends in HSV-1 and HSV-2 seroprevalence in the United States in 1999-2004
compared with 1988-1994.
Cross-sectional, nationally representative surveys (US National Health and Nutrition
Examination Surveys [NHANES]), were used to compare national seroprevalence estimates
from 1999-2004 with those from 1988-1994, and changes in HSV-1 and HSV-2 seroprevalence
since 1976-1980 were reviewed. Persons aged 14 to 49 years were included in these
Seroprevalence of HSV-1 and HSV-2 antibodies based on results from type-specific immunodot
assays; diagnosis of genital herpes.
The overall age-adjusted HSV-2 seroprevalence was 17.0% (95% confidence interval [CI],
15.8%-18.3%) in 1999-2004 and 21.0% (95% CI, 19.1%-23.1%) in 1988-1994, a relative
decrease of 19.0% between the 2 surveys (95% CI, -28.6% to -9.5%; P<.001). Decreases
in HSV-2 seroprevalence were especially concentrated in persons aged 14 to 19 years
between 1988 and 2004. In adolescents aged 17 to 19 years and young adults, the decreases
in HSV-2 seroprevalence were significant even after adjusting for changes in sexual
behaviors. Among those infected with HSV-2, the percentage who reported having been
diagnosed with genital herpes was statistically different (14.3% in 1999-2004 and
9.9% in 1988-1994; P = .02). Seroprevalence of HSV-1 decreased from 62.0% (95% CI,
59.6%-64.6%) in 1988-1994 to 57.7% (95% CI, 55.9%-59.5%) in 1999-2004, a relative
decrease of 6.9% between the 2 surveys (95% CI, -11.6% to -2.3%; P = .006). Among
persons infected with HSV-1 but not with HSV-2, a higher percentage reported having
been diagnosed with genital herpes in 1999-2004 compared with 1988-1994 (1.8% vs 0.4%,
These data show declines in HSV-2 seroprevalence, suggesting that the trajectory of
increasing HSV-2 seroprevalence in the United States has been reversed. Seroprevalence
of HSV-1 decreased but the incidence of genital herpes caused by HSV-1 may be increasing.