Epidemiology of herpes simplex virus (HSV) infections is changing in developed countries, including Finland, where primary HSV infection is now currently being acquired close to reproductive age. HSV infections are usually subclinical, but oral HSV shedding is frequent, which can lead to viral transmission. In addition, HSV could be one of the co-factors of persistent human papillomavirus (HPV) infection, which can lead to oral epithelial dysplasia or oral cancer. 

This thesis is part of the longitudinal Finnish Family HPV Study of 329 families. The focus is on oral epithelial HSV carriage and its co-carriage with oral HPV, as well as HSV seroprevalence among pregnant women and their male spouses during a six-year follow-up study. We also evaluated the impact of pregnancy, sexual habits and demographic factors on acquisition of HSV infection. 

HSV seroprevalence was 59% (168/285) among these healthy young women 
near delivery and 53% (64/120) among their male spouses. HSV DNA in oral 
epithelium was common among seropositive couples, 19% (31/168) of the seropositive mothers’ and 20% (13/64) of the seropositive fathers’ oral specimens being HSV-1 DNA positive. HPV-HSV co-infection in a single oral specimen was rare. Age, genital HPV and the presence of genital warts were associated with HSV seropositivity, while young age was associated with HSV seroconversion in these women. Oral sex and urethral high-risk HPV was associated with HSV-seropositivity among the male spouses. 

To conclude, parents at childbearing age do acquire primary HSV infections in 
Finland, and HSV-1 DNA in oral epithelium is common among HSV seropositive subjects. Sexual habits may also contribute to HSV transmission among young women and men.