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Herpes simplex infection

Cold Sore, Fever Blister, Genital Herpes

What is Herpes simplex infection?

Herpes simplex infection is a contagious disease, characterized by recurrent painful blisters. It is caused by herpes simplex virus (HSV). A single viral infection may result in multiple episodes (recurrences) of disease.

The disease is difficult to control, because it is most infectious before symptoms or signs appear. There are two main types of HSV, and they typically cause infection in different areas. HSV-1 infections occur primarily in the mouth or eyes. HSV-2 usually infects the genital region.

How is it diagnosed?

History is of close contact with an infected person. Painful blisters are reported on either the mouth, genitals, or eye. Attacks usually repeat, recurring in the same location as the initial infection, so there may be a previous diagnosis of herpes simplex. Recurrent episodes of disease are usually preceded by burning or itching at the initial site of infection.

  • Oral infections may be preceded by fever and feelings of general ill-health (malaise). A painful "fever blister" appears on the lip. A sore throat and pain on swallowing may be reported, as infection can also occur inside the mouth and at the back of the throat.
  • Eye infection is characterized by sudden one-sided eye redness and pain, with blurred and diminished vision if the cornea is involved. There may also be tearing and swelling reported.
  • Genital infection may be accompanied by burning or itching, followed by rash and painful blisters on the penis or vulva; rectal infection may be reported. Fever and malaise are present. There can also be pain radiating down the thighs and legs, difficulty urinating, and constipation. Women may have a vaginal discharge and men may have a slight urethral discharge.

Physical exam will initially show groups of small, reddened areas, which then form blisters, become ulcerated, and then crust over. Swelling or tenderness of local lymph nodes may be present.

  • Oral infection usually is seen as blisters or ulcers on the edge of the lip; they may be seen inside the mouth or as tonsillitis.
  • Eye infection is seen as redness (conjunctivitis) in one eye, with blisters on the eyelid margin. A corneal ulceration, if present, has a characteristic shape (dendritic) and can recur after the initial infection.
  • Genital herpes infection shows crops of blisters on the penis, vulva, buttocks, or thighs. An inflammation of the cervix is often seen. Lymph nodes in the groin are usually enlarged.

Tests: Isolation of the virus from early blisters, and detection of HSV-specific antibodies in the blood, are ways to verify herpes simplex virus infections; these tests often fail to differentiate between virus subtypes, however.

How is Herpes simplex infection treated?

Herpes simplex infections are usually treated with over-the-counter medications to relieve the symptoms of itching, burning or pain associated with the lesions.

Antiviral drugs called nucleoside analogs may be used to accelerate the healing of primary herpes simplex infections, lessen the severity of recurrent infections or prevent maternal transmission to newborns during childbirth. These drugs inhibit growth of the virus and minimize the spread of infection, but they do not cure the disease or prevent recurrent infections. Widespread usage of nucleoside analogs has led to the emergence of nucleoside-resistant strains of the virus. These strains of virus are commonly seen in people who have a history of multiple herpes simplex infections or long-term nucleoside treatment. Effective treatment of nucleoside-resistant strains is usually achieved by switching drugs.


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Famvir (Famciclovir), Valtrex (Valacyclovir)

What might complicate it?

Urine retention may occur with genital herpes, due to pain or disturbed function of the autonomic nervous system. Individuals with impaired immunity are particularly susceptible to complications of herpes simplex, characterized by severe, persistent infections involving the mouth, face, genital or anal regions. Without antiviral drug treatment, these infections persist indefinitely and can spread to other parts of the body. Occasionally, the virus spreads through the bloodstream (viremia) and infects the esophagus, lungs, liver, adrenal glands or bone marrow. Rare instances of infections in the stomach, intestines and heart have been observed. Herpes simplex infection of the brain (encephalitis and meningitis) is a rare, but serious, complication.

Predicted outcome

The prognosis for herpes simplex disease is usually good. Complications of primary disease are typically few and short-lived. Symptoms decrease in severity with each episode of recurrent disease. The outcome of disease is less optimistic when a person cannot produce an effective immune response to the virus. These cases are more severe, last longer and often show long-term effects of the infection.


Oral infection may be confused with strep throat, aphthous stomatitis, and Stevens-Johnson syndrome. Eye infection may be similar to bacterial infection, trauma, or chemical conjunctivitis. Genital herpes can be confused with syphilis, chancroid, lymphogranuloma venereum, or cancer; rectal herpes could be gonorrhea or chlamydia infection. Often multiple organisms are present in these infections.

Appropriate specialists

Urologist, neurologist and obstetrician.

Last updated 4 April 2018