Recurrent herpes labialis and Herpes simplex virus-1 genitalis: what is the link?

BACKGROUND: Recently, Herpes simplex virus (HSV)-1 seroprevalence declined among adolescents, rendering young people lacking HSV-1 antibodies more susceptible to genital HSV-1 acquisition, if sexually exposed. The aim of the present study was to identify the possible risk factors for the development of HSV-1 related Herpes genitalis (HG). METHODS: From January 2012 to December 2015, patients with HG attending three Sexually Transmitted Infections Units in Northern Italy were recruited. A genital swab on the lesions for the search of HSV-1/2 DNA through real time polymerase chain reaction (PCR) and a serum sample for HSV-1/2 specific serology were performed. Moreover, patients were asked whether they had personal history of herpes labialis (HL). Patients with PCR proved HSV-1 HG were included as cases; asymptomatic subjects attending STI Units for a blood check were recruited as controls and were checked for HSV-1/2 serology. RESULTS: The study included 141 cases and 70 controls. Specific HSV-1 antibodies were found in 34.7% of the cases and 67% of the controls. History of recurrent herpes labialis (RHL) was found in 4% of the cases and 31% of the controls. The occurrence of RHL in HSV-1 seropositive patients resulted lower in the case group compared to the control group. CONCLUSIONS: We can speculate about a protective role for RHL against the clinical appearance of HSV-1 HG. The clinical usefulness of our study involved especially the counselling in serodiscordant couples. The presence of HSV-1 antibodies in asymptomatic sexual partners does appear protective for HG manifestation only in presence of RHL history.