Herpes is one of the most common infections in the world. An estimated 3.8 billion people under age 50, roughly 64% of the global population, carry herpes simplex virus type 1 (HSV-1). Another 520 million people aged 15 to 49, about 13% worldwide, carry herpes simplex virus type 2 (HSV-2). In the United States specifically, nearly half of people aged 14 to 49 have HSV-1, and about 1 in 8 have HSV-2. By almost any measure, herpes is extraordinarily prevalent, yet most people who carry it don’t know they’re infected.
Global Prevalence by the Numbers
The World Health Organization’s most recent estimates, based on 2020 data, put HSV-1 at 3.8 billion infections among people under 50. HSV-1 is primarily known for causing oral herpes (cold sores), though it increasingly causes genital infections as well. HSV-2, the virus traditionally linked to genital herpes, affects an estimated 520 million people aged 15 to 49 worldwide.
These numbers vary significantly by region. Africa and the Americas both have high genital herpes prevalence (above 19%), but for different reasons. In the Americas, genital HSV-1 accounts for a larger share of cases, with prevalence above 9%. In Africa, genital herpes is driven almost entirely by HSV-2. Southeast Asia carries a moderate HSV-2 burden, while genital HSV-1 is less common in both Africa and Southeast Asia.
How Common Herpes Is in the United States
National survey data from 2015 to 2016 found that 47.8% of Americans aged 14 to 49 tested positive for HSV-1, and 11.9% tested positive for HSV-2. That translates to tens of millions of people carrying each virus. The CDC estimates that 572,000 new genital herpes infections occurred in 2018 alone among people in that age range.
Prevalence climbs steadily with age, which makes sense for a lifelong virus that accumulates in the population over time. For HSV-1, about 27% of 14- to 19-year-olds test positive, rising to 41.3% in the 20 to 29 group, 54.1% in the 30 to 39 group, and 59.7% among those aged 40 to 49. HSV-2 follows a similar pattern but starts much lower: just 0.8% of teenagers test positive, compared to 7.6% of people in their 20s, 13.3% in their 30s, and 21.2% in their 40s. By middle age, roughly 1 in 5 Americans carries HSV-2.
Disparities by Gender and Race
Herpes does not affect all groups equally. Women have higher prevalence rates than men for both virus types, partly because the virus transmits more easily from men to women during sex. The demographic gaps for HSV-2 are especially stark when race is factored in.
Among women aged 20 to 24, Black women have an HSV-2 prevalence of about 35%, compared to roughly 7% for white, Hispanic, and other women in the same age group. By ages 45 to 49, that gap widens further: approximately 66.5% of Black women test positive for HSV-2, versus 31.4% of women in other racial and ethnic groups. Among men, the pattern holds. About 18% of Black men aged 20 to 24 carry HSV-2, compared to 3.4% of their white, Hispanic, and other-race peers. By the late 40s, 46% of Black men test positive versus about 17% of other men.
These disparities reflect differences in sexual network patterns, access to healthcare, and broader social determinants of health rather than any biological susceptibility. They highlight that herpes prevalence figures can look very different depending on which population you examine.
Most People Don’t Know They Have It
One of the most important facts about herpes prevalence is how invisible the infection usually is. Only 10% to 40% of people with genital herpes are aware of their infection. The remaining 60% to 90% have never been diagnosed. Among that undiagnosed group, roughly half actually do experience recognizable symptoms but have never connected them to herpes. These individuals can often learn to identify typical outbreaks once they know what to look for. The remaining third of all infected people are truly asymptomatic, experiencing no noticeable symptoms at all, though they can still shed the virus and transmit it to others.
This invisible majority is a major reason herpes spreads so effectively. Standard STI screening panels typically do not include herpes blood tests unless you specifically request one, which means many carriers go their entire lives without knowing their status.
HSV-1 Is Increasingly Causing Genital Herpes
The traditional divide between “oral herpes from HSV-1” and “genital herpes from HSV-2” has been shifting for decades. In several high-income countries, including the United States, Canada, and much of Western Europe, HSV-1 has become the leading cause of first-episode genital herpes, particularly among adolescents and young adults. Genital HSV-1 cases are rising by 1 to 2% annually in many areas.
The likely explanation is paradoxical. As oral HSV-1 prevalence declines among younger generations (due to improved hygiene and less childhood exposure), more teenagers and young adults reach sexual debut without HSV-1 antibodies. That leaves them vulnerable to catching HSV-1 genitally through oral sex. In Africa, Latin America, and Southeast Asia, where childhood HSV-1 infection remains common, HSV-2 still dominates genital herpes cases.
Prevalence Trends Over Time
Despite how common herpes remains, both HSV-1 and HSV-2 prevalence have been declining in the U.S. over the past several decades. HSV-1 rates have dropped noticeably among younger age groups, likely due to changes in hygiene practices and less crowded household conditions that reduce childhood transmission. HSV-2 has also shown gradual declines. The 2015 to 2016 survey figure of 11.9% is lower than rates measured in earlier decades.
However, declining prevalence doesn’t necessarily mean fewer problems. As fewer young people enter adulthood with existing HSV-1 antibodies, they lose the partial cross-protection those antibodies once provided against HSV-2 and genital HSV-1. This shifting immunity landscape is one reason genital HSV-1 infections continue to rise even as overall HSV-1 carriage drops.
Neonatal Herpes Transmission
While herpes is usually a manageable condition in adults, it poses serious risks to newborns. Between 2017 and 2021, an average of 379 neonatal herpes cases were diagnosed per year in the United States, for an overall incidence of about 10 cases per 100,000 live births. Neonatal herpes can cause severe illness, making maternal herpes status an important consideration during pregnancy and delivery.