About two-thirds of the global population under age 50 has HSV-1. The World Health Organization estimates that 3.8 billion people, or 64% of that age group, were living with the infection as of 2020. In the United States, the number is lower but still substantial: roughly 48% of people aged 14 to 49 test positive for HSV-1 antibodies.
Global Numbers by Region
HSV-1 prevalence varies dramatically depending on where you live. Africa has the highest rates, with about 87% of people under 50 carrying the virus regardless of sex. The Eastern Mediterranean region follows at around 75%, and the Western Pacific (which includes China, Japan, and Australia) sits near 73-74%.
Europe falls in the middle, with roughly 69% of women and 61% of men infected. The Americas have the lowest regional prevalence globally: about 49% of women and 39% of men. These figures help explain why someone in sub-Saharan Africa is far more likely to encounter HSV-1 in early childhood than someone growing up in the U.S. or Canada.
Prevalence in the United States
The most detailed U.S. data comes from the 2015-2016 National Health and Nutrition Examination Survey, which tested blood samples from a representative cross-section of the population. Among Americans aged 14 to 49, the age-adjusted prevalence was 48.1%. That means just under half of people in that age range have been infected at some point, whether or not they’ve ever had a visible cold sore.
Prevalence climbs steadily with age. Only 27% of teenagers (14-19) tested positive, compared to 41.3% of people in their twenties, 54.1% in their thirties, and 59.7% in their forties. Women are slightly more likely to carry the virus (50.9%) than men (45.2%). Rates also differ across racial and ethnic groups: 71.7% among Mexican-American participants, 58.8% among non-Hispanic Black participants, 55.7% among non-Hispanic Asian participants, and 36.9% among non-Hispanic white participants.
Why Rates Are Shifting
HSV-1 used to be something most people picked up as young children, passed along through casual contact like a kiss from a relative or sharing utensils. In higher-income countries, that pattern has been changing. Better hygiene, less crowded living conditions, and smaller household sizes mean fewer children are exposed early in life. The 27% prevalence among U.S. teenagers reflects this shift.
That sounds like good news, and in some ways it is. But it creates an unexpected tradeoff. People who don’t encounter HSV-1 as children have no antibodies against it, which means they’re susceptible to catching it for the first time as a teenager or adult. When that happens, the virus is more likely to be transmitted through sexual contact rather than the casual childhood contact that was once the norm. The WHO has noted that genital HSV-1 infections are rising even as childhood oral infections decline. An estimated 376 million people worldwide had genital HSV-1 in 2020, up from earlier estimates.
Most People Don’t Know They Have It
The gap between the number of people who test positive for HSV-1 antibodies and the number who know they’re infected is enormous. The majority of people carrying HSV-1 never develop recognizable symptoms, or their symptoms are so mild they attribute them to something else, like a chapped lip or irritated skin. Standard STI panels typically don’t include herpes blood tests, which means most carriers are never formally diagnosed.
Even without symptoms, the virus can still be transmitted. HSV-1 periodically reactivates and sheds from the skin or mucous membranes, sometimes producing no visible sore at all. This “asymptomatic shedding” is a major reason the virus is so widespread. Someone who has never had a cold sore in their life can still carry and pass along HSV-1.
HSV-1 vs. HSV-2
HSV-1 is far more common than its close relative, HSV-2. In the U.S., only about 12% of people aged 14 to 49 have HSV-2, compared to 48% for HSV-1. The two viruses are biologically similar but tend to behave differently. HSV-1 traditionally causes oral infections (cold sores) and reactivates less frequently when it infects the genital area. HSV-2 is the more common cause of recurrent genital herpes and is almost exclusively sexually transmitted.
The distinction between the two types is becoming blurrier, though. As more people acquire HSV-1 through sexual contact in adulthood rather than through childhood exposure, genital HSV-1 is accounting for a growing share of new genital herpes diagnoses in many countries. In practical terms, the location of the infection matters more than the type number when it comes to symptoms and transmission risk.