Herpes simplex

Definition of Herpes simplex

Herpes simplex is a viral infection that mainly affects the mouth or genital area.

Causes, incidence, and risk factors

There are two strains of herpes simplex viruses:

Signs and tests

Many times, doctors can tell whether you have an HSV infection simply by looking at the sores. However, certain tests may be ordered to be sure of the diagnosis. These tests include:


Some cases are mild and may not need treatment.

Expectations (prognosis)

The oral or genital lesions usually heal on their own in 7 to 10 days. The infection may be more severe and last longer in people who have a condition that weakens the immune system.


David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School, Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. – 5/30/2009

Herpetic whitlow on the thumb
Herpes simplex - close-up

ADAM Medical Encyclopedia

Article written by

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability.