Herpes simplex virus is one of the most common infections on the planet. In the United States alone, roughly 48% of people aged 14 to 49 carry HSV-1, and about 12% carry HSV-2, based on CDC data from the 2015–2016 national health survey. Globally, the numbers are even larger, with billions of people carrying one or both types of the virus.
HSV-1 and HSV-2: Two Different Viruses, Different Patterns
HSV-1 is the more widespread of the two types. Most people pick it up during childhood through nonsexual contact like a kiss from a parent or sharing utensils. It traditionally causes oral herpes (cold sores), though it increasingly causes genital infections as well. In the U.S., prevalence climbs steadily with age: about 27% of teenagers aged 14 to 19 carry HSV-1, rising to 41% in the 20s, 54% in the 30s, and nearly 60% by the 40s.
HSV-2 is primarily spread through sexual contact and is the virus most associated with genital herpes. It’s far less common than HSV-1 but still affects a significant share of the population. Among Americans aged 14 to 49, prevalence starts below 1% in teenagers, then rises to about 8% in the 20s, 13% in the 30s, and 21% in the 40s. Women are infected at higher rates than men, partly because the virus transmits more easily from male to female during sex.
The Numbers Are Likely Higher Than Reported
The CDC’s national survey does not include people who are incarcerated or homeless, groups that tend to have higher infection rates. That means the official U.S. figures of 48% for HSV-1 and 12% for HSV-2 are probably conservative estimates.
More strikingly, over 80% of people with HSV-2 don’t know they have it. Their infections are either completely asymptomatic, produce symptoms mild enough to go unnoticed, or get misdiagnosed because they don’t look like the textbook genital sores most people picture. Standard STI panels typically do not include herpes blood tests unless you specifically ask, which means many carriers never get tested at all.
HSV-1 Is Changing the Picture of Genital Herpes
One of the biggest shifts in herpes epidemiology over recent decades is the growing role of HSV-1 in genital infections. A 2023 meta-analysis found that HSV-1 now accounts for about 37% of genital herpes cases worldwide. In younger populations the proportion is even higher. Among a large study of students aged 16 to 21, HSV-1 was responsible for 78% of all genital herpes isolates.
This shift is happening in part because fewer young people are catching HSV-1 as children. That sounds like good news, but it has a paradoxical effect: without childhood oral infection providing some immune protection, teenagers and young adults encountering HSV-1 for the first time through oral sex are more vulnerable to genital infection. The pattern varies dramatically by region. In Africa, HSV-1 causes only about 1% of genital herpes cases, likely because childhood oral infection remains extremely common there.
How Prevalence Changes With Age
Both HSV-1 and HSV-2 become more common as people get older, but for different reasons. HSV-1 prevalence rises partly because more years of life mean more chances for casual exposure, and the virus never leaves the body once acquired. HSV-2 prevalence increases because cumulative sexual exposure grows over time. By your 40s, you are roughly 26 times more likely to carry HSV-2 than a teenager, based on the jump from 0.8% prevalence in 14- to 19-year-olds to 21.2% in 40- to 49-year-olds.
The highest number of new HSV-2 infections, however, occurs in adolescents and young adults. So while older adults have the highest overall prevalence because the virus is lifelong, the peak window for first catching HSV-2 is earlier in life.
What These Numbers Mean in Practical Terms
If you’re in a room with ten American adults in their 40s, statistically about six of them carry HSV-1 and two carry HSV-2. Some carry both. The vast majority have never had a noticeable outbreak or have had symptoms so mild they attributed them to something else, like razor burn or a yeast infection.
Because herpes is so common and so often invisible, the gap between actual infections and diagnosed cases is enormous. Routine screening isn’t recommended for people without symptoms, partly because the psychological burden of a positive test often outweighs the clinical significance for someone who has never had an outbreak. This policy choice keeps official case counts low even as actual prevalence remains high.
For people who do experience outbreaks, the first episode is typically the worst, and recurrences tend to become less frequent over the years. HSV-2 recurs more often than genital HSV-1, which is one reason the type of virus matters even when the location of infection is the same. Antiviral medications can reduce outbreak frequency and lower the risk of transmitting the virus to a partner, but they do not eliminate the virus from the body.