Herpes simplex

Herpes is an infection caused by herpes simplex virus 1 or 2. It primarily affects the mouth or genital area.

Causes, incidence, and risk factors

There are two different strains of herpes simplex viruses. Herpes simplex virus type 1 (HSV-1) is usually associated with infections of the lips, mouth, and face. It is the most common herpes simplex virus among the general population and is usually acquired in childhood.

HSV-1 often causes lesions inside the mouth such as cold sores (fever blisters) and is transmitted by contact with infected saliva. By adulthood, up to 90% of individuals will have antibodies to HSV-1.

Herpes simplex virus 2 (HSV-2) is sexually transmitted and is usually associated with genital ulcers or sores. Individuals may, however, harbor HSV-2 and not have developed any symptoms. Up to 30% of U.S. adults have antibodies against HSV-2. Cross-infection of type 1 and 2 viruses may occur from oral-genital contact.

In addition to oral and genital lesions, the virus can also lead to complications such as meningoencephalitis (infection of the lining of the brain and the brain itself) or cause infection of the eye - in particular the conjunctiva, and cornea.

A finger infection, called herpetic whitlow is another form of herpes infection - usually affecting health care providers (because of exposure to oral secretions during procedures) and young children. The herpes virus may also infect the fetus and cause congenital abnormalities.

Herpes viruses can be transmitted to a newborn during vaginal delivery in mothers infected with herpes viruses (especially if the mother has active infection at the time of delivery, yet transmission may still occur at a lower rate without visible lesions).

The virus may be transmitted even in the absence of symptoms or visible lesions. Once the virus is acquired, it spreads to nerve cells and remains dormant. It may intermittently reactivate and cause symptoms (flares). Recurrences may be precipitated by overexposure to sunlight, fever, stress, acute illness, and medications or conditions that weaken the immune system (such as cancer, HIV/AIDS, and use of corticosteroids).


  • mouth sores  
  • genital lesions (male) - may be preceded by burning or tingling sensation  
  • genital lesions (female) - may be preceded by burning or tingling sensation  
  • blisters and/or ulcers - most frequent on the mouth, lips and gums or genitalia  
  • fever blisters  
  • fever - may be present especially during the first episode  
  • enlargement of lymph nodes in the neck or groin

Signs and tests
In many instances, the physical appearance of the lesions is highly suggestive of the diagnosis of herpes-simplex infections. However, to establish a definitive diagnosis - certain tests may be used including a blood test, a viral culture of lesion, a Tzanck test, or a direct fluorescent antibody (DFA) test.

Some cases are relatively mild and may not require treatment. In severe or prolonged cases, as well as in individuals who are immunosuppressed or who have frequent recurrences, antiviral medications such as acyclovir or its derivatives may be used. In individuals with more than 6 recurrences of genital herpes per year, chronic antiviral medications may be offered to reduce recurrences.

Support Groups
Support Groups and dating services are available for people with genital herpes and may help people cope with the disorder.

Expectations (prognosis)
The oral or genital lesions usually heal on their own in 7 to 10 days unless an individual has an underlying condition that weakens the immune system, in which case the infection may be more severe and last longer.

Once infected, the virus stays in the body for the rest of a person’s life and recurrences of active infection may occur. Recurrences may be precipitated by overexposure to sunlight, fever, stress, acute illness, and medications or conditions that weaken the immune system (such as cancer, HIV/AIDS, or use of corticosteroids).


  • meningitis  
  • encephalitis  
  • eczema herpetiform (widespread herpes across the skin)  
  • infection of the eye - keratoconjunctivitis  
  • prolonged, severe infection in immunosuppressed individuals  
  • pneumonia  
  • infection of the trachea

Calling your health care provider

Call your health care provider if you develop symptoms which appear to be herpes infection as there are many different conditions which can cause similar lesions (particularly in the genital area).

If you have a history of herpes infection and you develop similar lesions, notify your health care provider if they do not resolve after 7-10 days, or if you have a condition that weakens your immune system.


Prevention is difficult since the virus can be spread to others when the infected person has no evidence of a current outbreak; however, avoiding direct contact with an open lesion will lower the risk of infection.

People with genital herpes should avoid sexual contact when active lesions are present. Safer sex behaviors including the use of condoms may also lower the risk of infection.

Individuals with active herpetic lesions should also avoid contact with newborns, children with eczema or immunosuppressed individuals as these groups are at higher risk for more severe disease.

In pregnant women with active herpes simplex infection at the time of delivery, a cesarean delivery (C-section) is recommended to decrease the risk of infecting the newborn.

Johns Hopkins patient information

Last revised: December 5, 2012
by David A. Scott, M.D.

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.