Canker sores are sometimes thought to be caused by HSV, but this is not true. Canker sores occur only inside the mouth, on the tongue, and on the soft palate (roof of mouth), not on skin surfaces. Although they reoccur, they are not contagious, usually are self-limiting, and have almost no complications. Canker sores are caused by substances that irritate the lining of the mouth.
Avoid touching any sores you have. If you do, wash your hands with soap and water. You should avoid sex while you have sores, and use a male or female condom or dental dam with your partner if sex occurs despite intentions to not have sex. Herpes is most contagious during an outbreak, but it’s also possible to spread herpes when no symptoms are present.
Human herpes virus 8 (HHV8) was recently discovered in the tumours called Kaposi's Sarcoma (KS). These tumours are found in people with AIDS and are otherwise very rare. KS forms purplish tumours in the skin and other tissues of some people with AIDS. It is very difficult to treat with medication. HHV8 may also cause other cancers, including certain lymphomas (lymph node cancers) associated with AIDS. The fact that these cancers are caused by a virus may explain why they tend to occur in people with AIDS when their immune systems begin to fail. The discovery also provides new hope that specific treatments for these tumours will be developed that target the virus.

The cell this virus targets is the B lymphocyte. These cells mature in the bone marrow and are a type of mononuclear leukocyte cells - white blood cells with a one-lobed nucleus. The incubation period for the Epstein – Barr Virus (EBV) is about 30 to 50 days, and patients typically have enlarged lymph nodes and spleens. Some patients have signs of hepatitis.
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.
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