HSV-2 is contracted through forms of sexual contact with a person who has HSV-2. An estimated 20 percent of sexually active adults in the United States are infected with HSV-2, according to the American Academy of Dermatology (AAD). HSV-2 infections are spread through contact with a herpes sore. In contrast, most people get HSV-1 from an infected person who is asymptomatic, or does not have sores.
The most common reason that people develop cold sores on their mouths is due to becoming infected with HSV-1. (4) HSV-1 usually causes cold sore breakouts around the lips or mouth, or what some people describe as “fever blisters.” Someone can become infected with HSV-1 starting as a child, and then the virus can lay dormant in the body until the immune system is weakened, at which point symptoms can surface.
A doctor will base a presumptive diagnosis on information provided by the patient and on the physical examination. The characteristic appearance of the herpes sores leaves little doubt about the diagnosis, so the typical appearance of the sores is key to the diagnosis. This appearance helps distinguish oral herpes from oral thrush, shingles, gonorrhea, and syphilis. In addition, chapped or sunburned lips can resemble oral herpes, but the tissue stain (Tzanck smear, see below) shows no virus-induced cell changes. Further testing is usually not necessary but is sometimes done.