Syphilis infection in the United States mainly occurs between sexually active adults aged from 20 to 29, with around 20,000 to 30,000 cases reported per year. <!-- Should we estimate how many cases go unreported? --> | Syphilis infection in the United States mainly occurs between sexually active adults aged from 20 to 29, with around 20,000 to 30,000 cases reported per year. <!-- Should we estimate how many cases go unreported? --> |