Quantifying population-level sexual risk behavior through HSV-2 transmission dynamics in the United States, 1950–2020

The risk of acquiring a sexually transmitted infection, such as herpes simplex virus type 2 (HSV-2), is shaped by sexual risk behavior-an aggregate measure influenced not only by an individual's sexual behavior but also by the broader sexual network. This study quantified the temporal and age-specific variations in sexual risk behavior for HSV-2 infection in the United States population between 1950 and 2020. A population-level mathematical model was used to describe HSV-2 transmission and was calibrated with ten rounds of nationally representative, population-based data from the National Health and Nutrition Examination Survey (NHANES). The model produced robust fits to the age-specific, sex-specific, and temporal HSV-2 seroprevalence data across the NHANES rounds. Sexual risk behavior gradually increased starting in the early 1960s, peaked in the early 1980s, and then steadily declined through 2020. The decline was particularly pronounced in the 1990s, when sexual risk behavior dropped sharply compared to the elevated levels of the early 1980s. Sexual risk behavior was highest among individuals aged 15-24 years and steadily declined with increasing age. The analysis identified a distinct wave of sexual risk behavior that began in the early 1960s, peaked in the early 1980s, and subsequently declined.