What total percentage of the population has either herpes simplex virus type 1 (HSV‑1) or herpes simplex virus type 2 (HSV‑2)?

Global Prevalence of HSV-1 or HSV-2 Infection

Approximately 67-70% of the global population has either HSV-1 or HSV-2 infection, driven predominantly by the extremely high prevalence of HSV-1 (66.6% globally) with HSV-2 adding an additional 13.2% among those aged 15-49 years, accounting for minimal overlap between the two infections.

Global Burden Estimates

The most comprehensive global analysis provides definitive prevalence data for 2016 1:

• HSV-1 prevalence: 66.6% of people aged 0-49 years worldwide (3.75 billion people) have HSV-1 infection at any anatomical site 1
• HSV-2 prevalence: 13.2% of people aged 15-49 years (491.5 million people) have HSV-2 infection 1
• Genital HSV-1: Approximately half a billion people have genital infection with either HSV-1 or HSV-2 combined 1

Updated 2020 Estimates

More recent modeling for 2020 shows similar patterns 2:

• HSV-2: 13.3% prevalence (519.5 million people aged 15-49 years) with 25.6 million new infections annually 2
• Genital HSV-1: 10.2% prevalence (376.2 million people aged 15-49 years) with 16.8 million new infections annually 2

Key Epidemiologic Patterns

Age-related acquisition differs markedly by virus type:

• HSV-1 is typically acquired during childhood through non-sexual contact, with seroprevalence increasing progressively with age 1, 3
• HSV-2 is almost exclusively sexually transmitted and acquired later in life 4, 1

Geographic variation is substantial:

• HSV-2 prevalence is highest in the WHO African Region 1
• Regional HSV prevalence estimates may not be generalizable across populations due to marked geographic differences 5

Sex-based differences:

• Women consistently have higher HSV-2 seroprevalence than men across all age groups 1, 6
• This pattern holds for both HSV-1 and HSV-2 infections 6

Temporal Trends in the United States

HSV-1 seroprevalence is declining:

• Decreased from 62.0% (1988-1994) to 57.7% (1999-2004), representing a 6.9% relative decline 3
• More recent data shows pooled seroprevalence of 38.0% in children and 63.5% in adults, with rates declining by 0.99-fold per year 7

HSV-2 seroprevalence has also declined:

• Decreased from 21.0% (1988-1994) to 17.0% (1999-2004), a 19.0% relative decline 3
• Decreases were especially pronounced in adolescents aged 14-19 years 3

Genital HSV-1 is increasing:

• The proportion of HSV-1 detection in genital herpes cases is rising by 1.02-fold per year 7
• Among those with HSV-1 (but not HSV-2), more reported genital herpes diagnoses in 1999-2004 (1.8%) versus 1988-1994 (0.4%) 3

Clinical Implications of Dual Infection

Co-infection rates are relatively low:

• Only 4% of participants in a Japanese population-based study had both HSV-1 and HSV-2 antibodies 6
• Prior HSV-1 infection reduces the likelihood of subsequent HSV-2 acquisition and mitigates clinical severity of genital HSV-2 disease when it does occur 5, 6

Important Caveats

Most infections are unrecognized:

• The majority of individuals infected with HSV-2 are unaware of their infection 8
• Only 14.3% of those with HSV-2 antibodies reported having been diagnosed with genital herpes (1999-2004 data) 3

Anatomical site cannot reliably predict virus type:

• While HSV-1 traditionally causes oral infection and HSV-2 causes genital infection, oro-genital sexual practices have blurred this distinction 4
• HSV-1 has become an important cause of genital herpes in developed countries 3