Most of us finished medical school repeating the mantra “herpes simplex type 1 (HSV-1)=orolabial herpes; herpes simplex type 2 (HSV-2)=genital herpes”. However, the passage of time has taught us that this is not always the case and that HSV-1 is increasingly found in the anogenital area, as reported by Magdaleno et al.1 In their observational study in a sexually transmitted infections unit in Valencia, the authors found that 47.3% of cases of genital herpes were caused by HSV-1 and that this type was even more frequent in women (59.3%). Furthermore, women with genital herpes caused by HSV-1 were younger than those with infection caused by HSV-2 (26 vs. 34 years, respectively; P=.015), and infections caused by HSV-2 were more associated with recurrences than those caused by HSV-1.

The most recent studies estimate that the overall seroprevalence of HSV-2 infection is <10% in Europe, the eastern Mediterranean area, Southeast Asia, and parts of the western Pacific region. Moreover, it seems that this prevalence has been decreasing in our setting in recent years.2 HSV-1, on the other hand, is currently confirmed as the most common cause of primary genital herpes infection in developed countries, especially in women and in men who have sex with men aged under 25 years.3 The reduced seroprevalence of HSV-1 has led us to consider a scenario in which adolescents and young adults first become exposed to HSV-1 at the onset of sexual activity. Both this circumstance and the increasing frequency of unprotected oral-genital practices may help to explain why HSV-1 is more prevalent as the causal agent of genital herpes than HSV-2. The resulting implications affect not only the epidemiology of the disease, but also its prognosis, since it seems that HSV-1 is associated with a lower frequency of recurrences.