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]James C, Harfouche M, Welton NJ, et al. Herpes simplex virus: global infection prevalence and incidence estimates, 2016. Bull World Health Organ. 2020 May 1;98(5):315-29.
https://www.doi.org/10.2471/BLT.19.237149
http://www.ncbi.nlm.nih.gov/pubmed/32514197?tool=bestpractice.com
Worldwide, it is estimated that 67% of persons ages 0-49 years are infected with herpes simplex virus type 1 (HSV-1).[3]Looker KJ, Magaret AS, May MT, et al. Global and regional estimates of prevalent and incident herpes simplex virus type 1 infections in 2012. PLoS One. 2015 Oct 28;10(10):e0140765.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4624804
http://www.ncbi.nlm.nih.gov/pubmed/26510007?tool=bestpractice.com
HSV-1 is most commonly acquired during childhood, and seroprevalence increases with age. Among US adults ages 14-49 years, 47.8% are infected with HSV-1 and 11.9% are infected with HSV type 2 (HSV-2).[4]McQuillan G, Kruszon-Moran D, Flagg EW, et al. Prevalence of herpes simplex virus type 1 and type 2 in persons aged 14–49: United States, 2015–2016. NCHS Data Brief, no 304. February 2018 [internet publication].
https://www.cdc.gov/nchs/products/databriefs/db304.htm
Prevalence of both HSV-1 and HSV-2 is higher among women than men.[3]Looker KJ, Magaret AS, May MT, et al. Global and regional estimates of prevalent and incident herpes simplex virus type 1 infections in 2012. PLoS One. 2015 Oct 28;10(10):e0140765.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4624804
http://www.ncbi.nlm.nih.gov/pubmed/26510007?tool=bestpractice.com
[5]Spicknall IH, Flagg EW, Torrone EA. Estimates of the prevalence and incidence of genital herpes, United States, 2018. Sex Transm Dis. 2021 Apr 1;48(4):260-5.
https://journals.lww.com/stdjournal/Fulltext/2021/04000/Estimates_of_the_Prevalence_and_Incidence_of.9.aspx
http://www.ncbi.nlm.nih.gov/pubmed/33492103?tool=bestpractice.com
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]Fanfair RN, Zaidi A, Taylor LD, et al. Trends in seroprevalence of herpes simplex virus type 2 among non-Hispanic blacks and non-Hispanic whites aged 14 to 49 years: United States, 1988 to 2010. Sex Transm Dis. 2013 Nov;40(11):860-4.
http://www.ncbi.nlm.nih.gov/pubmed/24113408?tool=bestpractice.com
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 ages 15-49 years are living with genital HSV-1, a prevalence of 4%.[3]Looker KJ, Magaret AS, May MT, et al. Global and regional estimates of prevalent and incident herpes simplex virus type 1 infections in 2012. PLoS One. 2015 Oct 28;10(10):e0140765.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4624804
http://www.ncbi.nlm.nih.gov/pubmed/26510007?tool=bestpractice.com
Of STI clinic attendees, 30% to 50% are HSV-2 seropositive, and 20% to 30% of women in US prenatal clinics are HSV-2 seropositive.[7]Patton ME, Bernstein K, Liu G, et al. Seroprevalence of herpes simplex virus types 1 and 2 among pregnant women and sexually active, nonpregnant women in the United States. Clin Infect Dis. 2018 Oct 30;67(10):1535-42.
https://academic.oup.com/cid/article/67/10/1535/4970884
http://www.ncbi.nlm.nih.gov/pubmed/29668856?tool=bestpractice.com
[8]Gottlieb SL, Douglas JM Jr, Schmid DS, et al. Seroprevalence and correlates of herpes simplex virus type 2 infection in five sexually transmitted-disease clinics. J Infect Dis. 2002 Nov 15;186(10):1381-9.
https://academic.oup.com/jid/article/186/10/1381/829952
http://www.ncbi.nlm.nih.gov/pubmed/12404152?tool=bestpractice.com
From 10% to 25% of HSV-2 seropositive people have a history of genital herpes lesions; most have mild and unrecognized disease.[9]Gupta R, Warren T, Wald A. Genital herpes. Lancet. 2007 Dec 22;370(9605):2127-37.
http://www.ncbi.nlm.nih.gov/pubmed/18156035?tool=bestpractice.com
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]Corey L. Wald A, Celum CL, et al. The effects of herpes simplex virus-2 on HIV-1 acquisition and transmission: a review of two overlapping epidemics. J Acquir Immune Defic Syndr. 2004 Apr 15;35(5):435-45.
http://www.ncbi.nlm.nih.gov/pubmed/15021308?tool=bestpractice.com
[11]Freeman E, Weiss HA, Glynn JR, et al. Herpes simplex virus 2 infection increases HIV acquisition in men and women: systematic review and meta-analysis of longitudinal studies. AIDS. 2006 Jan 2;20(1):73-83.
http://www.ncbi.nlm.nih.gov/pubmed/16327322?tool=bestpractice.com
Recurrence rates of genital HSV-2 are more frequent than oral-labial and genital HSV-1 infections.[12]Lafferty WE, Coombs RW, Benedetti J, et al. Recurrences after oral and genital herpes simplex virus infection. Influence of site of infection and viral type. N Engl J Med. 1987 Jun 4;316(23):1444-9.
http://www.ncbi.nlm.nih.gov/pubmed/3033506?tool=bestpractice.com
Recurrence rates of genital HSV-2 tend to decline in most individuals over time, although the pattern is variable.[13]Benedetti J, Corey L, Ashley R. Recurrence rates in genital herpes after symptomatic first-episode infection. Ann Intern Med. 1994 Dec 1;121(11):847-54.
http://www.ncbi.nlm.nih.gov/pubmed/7978697?tool=bestpractice.com