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Medical Author:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

William C. Shiel Jr., MD, FACP, FACR

Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Oral Herpes (HSV-1) Causes

Herpes simplex virus (HSV) is a DNA virus that causes sores in and around the mouth. Two herpes subtypes may cause these sores.

• Herpes simplex virus (type 1, herpes-1or HSV-1), which causes about 80% of cases of oral herpes infections
• Other herpes simplex viruses (type 2, herpes-2 or HSV-2), which causes the other approximately 20%

These viruses enter the body through small cuts, abrasions, or breaks in the skin or mucous membranes. The majority enter after an uninfected person has direct contact with someone carrying the virus (either with or without noticeable lesions). Simply touching an infected person is often the way children get exposed. Adolescents and adults frequently get exposed by skin contact also but may get their first exposure by kissing or sexual contact, especially for HSV-2.

Oral lesions (and genital lesions) can reoccur. This happens because the HSV viruses are still alive but exist in nerve cells in a quiet, inactive (dormant) state,. Occasionally, conditions in the body (see Stage 3 above) allow the HSV to actively multiply, resulting in a new crop of lesions.

The HSV viruses multiply in the human cells by overtaking and utilizing most of the human cells functions. One of the HSV steps in multiplication is to take control of the human cell's nucleus and alter its structure. The altered nucleus (enlarged and lobulated or multinucleated) is what is used to help diagnose HSV infections by microscopic examination. The reason sores appear is because as they mature the many HSV particles rupture the human cell's membrane as they break out of the cell.