Background: Herpes simplex virus infections type 1 (HSV-1) and type 2 (HSV-2) are common, but the epidemiology of HSV disease is changing.
Methods: HSV-seronegative women, aged 18-30 years, who were in the control arm of the HERPEVAC Trial for Women were followed for 20 months for primary HSV infections.
Results: Of the 3438 evaluable participants, 183 became infected with HSV: 127 (3.7%) with HSV-1 and 56 (1.6%) with HSV-2. The rate of infection for HSV-1 (2.5 per 100 person-years) was more than twice that for HSV-2 (1.1 per 100 person-years). Most infections (74% of HSV-1 and 63% of HSV-2) occurred without recognized signs or symptoms of herpes disease. The HSV-2 infection rate was 2.6 times higher in non-Hispanic black participants than in Hispanics and 5.5 times higher than in non-Hispanic whites (P < .001), while the HSV-1 infection rate was 1.7 times higher in non-Hispanic whites than non-Hispanic blacks. Younger participants (18-22 years) were more likely to acquire HSV-1 infections and less likely to develop recognized disease than older participants. Overall, 84% of recognized disease cases were genital. No differences were noted in the clinical manifestations of genital HSV-1 vs genital HSV-2 disease. The clinicians' assessment that cases were caused by HSV was good when they assessed cases as clinically confirmed or unlikely (validated in 83% and 100% of cases, respectively).
Conclusions: HSV-1 is now more common than HSV-2 as a cause of oral and genital mucosal infections in young women, but there are important age and race differences.