That's according to the first global estimate of the prevalence (total number of cases) and incidence (number of new cases) of herpes simplex virus type 2 (HSV-2) infection.
Here are the estimates, published in the Bulletin of the World Health Organization and based on studies from around the world published in 2003:
- 536 million people aged 15-49 are infected with herpes simplex type 2 virus. That's 16% of people in that age range.
- Every year, 23.6 million people aged 15-49 become infected with the herpes simplex type 2 virus.
The estimates only focus on HSV-2 among people aged 15-49; data came from studies published in 2003. Genital herpes can also be caused by herpes simplex virus type 1 (HSV-1), but HSV-1 typically infects the mouth and HSV-2 typically infects the genitals. HSV-2 is usually spread through sex; it can also pass from mother to child during birth.
Most people with herpes simplex virus type 2 don't know they're infected and don't have symptoms, note the researchers, who work at Imperial College London and the World Health Organization (WHO).
HSV-2 prevalence was higher among women than men and varied across world regions. Western European men had the lowest prevalence rate (13%) and women in sub-Saharan Africa had the highest prevalence rate (70%).
The researchers caution that their estimates "should not be taken as being definitive," partly because some world regions had few HSV-2 studies to analyze.