What is the prevalence of oral Herpes Simplex Virus type 1 (HSV1)?

Prevalence of Oral HSV-1 Infection

HSV-1 infection affects approximately 3.7 billion people globally, representing about 67% of the world's population aged 0-49 years. 1

Global and Regional Prevalence

• HSV-1 is extremely common worldwide, with an estimated 3.75 billion people (95% uncertainty interval: 3.56-3.85 billion) having HSV-1 infection at any site as of 2016, equivalent to a global prevalence of 66.6% in individuals aged 0-49 years 1

• The prevalence of HSV-1 varies significantly by geographic region:

  • Highest prevalence is observed in Africa, South-East Asia, and Western Pacific regions 2
  • Eastern European countries (particularly Bulgaria) have higher seroprevalence rates compared to Northern European countries (England, Wales, Germany, Netherlands, Belgium, and Finland) 3
  • In Australia, a nationwide population-based survey reported HSV-1 seroprevalence of 76% in 1999-2000 3

• Recent data from Australia shows even higher seroprevalence, with pooled mean seroprevalence among healthy adults at 84.8% (95% CI 74.3-93.1%) 4

Demographic Patterns

• HSV-1 seroprevalence increases with age:

  • In Australia, seroprevalence was 70.2% among individuals <35 years of age and 86.9% among those ≥35 years 4
  • Seroprevalence increases by approximately 1.05-fold per year of age 4

• Gender differences exist in HSV-1 prevalence:

  • In Australia, HSV-1 seroprevalence was higher in women (80.4%) than in men (71.3%) 3
  • Female gender has been identified as a risk factor for herpes labialis 3

• Socioeconomic factors influence prevalence:

  • Higher socioeconomic status is associated with lower prevalence of HSV-1 3
  • Seroprevalence is inversely related to socioeconomic background 5

Changing Epidemiology

• The epidemiology of HSV-1 has changed dramatically in recent decades:

  • HSV-1 was traditionally acquired in childhood and adolescence through non-sexual contact 3
  • Seroprevalence rates for HSV-1 are declining in the USA 3
  • HSV-1 is increasingly becoming a cause of genital herpes, with at least 50% of new cases of genital herpes in developed countries now caused by HSV-1 3

• In Australia and New Zealand, HSV-1 epidemiology appears to be transitioning toward:

  • Less oral acquisition in childhood
  • More genital acquisition among youth 4

Risk Factors and Clinical Manifestations

• Risk factors for herpes labialis (cold sores) include:

  • Female gender
  • Older age (65-74 years)
  • White race/ethnicity
  • Frequent upper respiratory infections
  • Low lymphocyte counts 3

• Interestingly, smokers report fewer herpes labialis outbreaks than nonsmokers 3

• Primary HSV-1 infection can be either asymptomatic or cause self-limiting gingivostomatitis 3

• Recurrent episodes of herpes labialis can be triggered by:

  • Exposure to ultraviolet light
  • Fever
  • Psychological stress
  • Menstruation 3

Clinical Implications

• Recurrent episodes of herpes labialis can be frequent, painful, long-lasting, and disfiguring for infected patients 3

• In immunocompromised patients, episodes are usually longer and more severe, potentially involving the oral cavity or extending across the face 3

• The high prevalence of HSV-1 has important implications for public health, as millions of people may be at higher risk of acquiring HIV, particularly in regions with high HSV-2 prevalence 1