* Incubation period: For HSV-1, the amount of time between contact with the virus and the appearance of symptoms, the incubation period, is two to 12 days. Most people average about four days.

* Duration of illness: Signs and symptoms will last two to three weeks. Fever, tiredness, muscle aches, and irritability may occur.

o Pain, burning, tingling, or itching occurs at the infection site before the sores appear. Many patients have reported these symptoms prior to the appearance of sores or blisters. Then clusters of blisters erupt. These blisters break down rapidly and, when seen, appear as tiny, shallow, gray ulcers on a red base. A few days later, they become crusted or scabbed and appear drier and more yellow.

o Oral sores: The most intense pain caused by these sores occurs at the onset and may make eating and drinking difficult.

+ The sores may occur on the lips, gums, throat, the front of the tongue, the inside of the cheeks, and the roof of the mouth.

+ They may also extend down the chin and neck.

+ The gums may become mildly swollen, red-colored, and may bleed.

+ Neck lymph nodes often swell and become painful.

+ People in their teens and 20s may develop a painful throat with shallow ulcers and a grayish coating on the tonsils

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. Further testing is usually not necessary.

If a definitive diagnosis is needed, because, for example, the infection involves other organ systems, the doctor may conduct laboratory tests listed below:

* A sample (tissue or fluid) from the sores to identify the virus as HSV

* A viral culture analysis

* A staining test called the Tzanck smear (shows nonspecific cell nucleus changes due to HSV)

* Antigen and antibody studies (serologic and PCR tests to determine if infection is caused by HSV-1 or HSV- 2)