Epidemiology

In 2016, an estimated half a billion people worldwide had genital infection with herpes simplex virus type 1 (HSV-1) or HSV-2, and several billion had oral HSV-1 infection.[2] Worldwide, it is estimated that 67% of persons aged 0-49 years are infected with herpes simplex virus type 1 (HSV-1).[3]

HSV-1 is most commonly acquired during childhood, and seroprevalence increases with age. Among US adults aged 14-49 years, 47.8% are infected with HSV-1 and 11.9% are infected with HSV type 2 (HSV-2).[4] Prevalence of both HSV-1 and HSV-2 is higher among women than men.[3]​[5]​​​ Although, overall, HSV-2 seroprevalence has declined in cross-sectional surveys, a disproportionate representation by certain at-risk populations has persisted, particularly among non-Hispanic blacks.[6]

Additionally, rates of genital herpes due to HSV-1 in the US may be increasing. Worldwide, it is estimated that more than 140 million people aged 15-49 years are living with genital HSV-1, a prevalence of 4%.[3] Of STI clinic attendees, 30% to 50% are HSV-2 seropositive, and 20% to 30% of women in US antenatal clinics are HSV-2 seropositive.[7][8]​​​​ From 10% to 25% of HSV-2 seropositive people have a history of genital herpes lesions; most have mild and unrecognised disease.[9]​ 

Worldwide, HSV-2 is the most common cause of genital ulcer disease. HSV-2 infection is a risk factor for HIV-1 acquisition and transmission.[10][11]​​ In England, HSV-2 seroprevalence in 16-64-year-olds is 9.7%.[12]

Recurrence rates of genital HSV-2 are more frequent than oral-labial and genital HSV-1 infections.[13]​ Recurrence rates of genital HSV-2 tend to decline in most individuals over time, although the pattern is variable.[14]

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