Herpes Simplex Virus Infections
Herpes simplex virus (HSV) infection produces recurring episodes of small, painful, fluid-filled blisters on the skin or mucous membranes.
There are two types of herpes simplex virus, HSV-1 and HSV-2. HSV-1 is the usual cause of cold sores on the lips (herpes labialis (see Section 8, Chapter 112)) and sores on the cornea of the eye (herpes simplex keratitis (see Section 20, Chapter 230)). HSV-2 causes genital herpes. This distinction is not absolute: genital infections are sometimes caused by HSV-1. These infections can be transmitted by direct contact with sores and sometimes by contact with the oral and genital areas of chronically infected people in between episodes of sores.
HSV infections produce an eruption of tiny blisters on the skin or mucous membranes. After the eruption of blisters subsides, the virus remains in a dormant (latent) state inside the group of nerve cells (ganglia) that supply the nerve fibers to the infected area. Periodically, the virus reactivates, begins growing again, and travels through the nerve fibers back to the skin--causing eruptions of blisters in the same area of skin as the earlier infection. Sometimes the virus may be present on the skin or mucous membranes even when there is no obvious blister.
Reactivation of latent oral or genital HSV infection may be triggered by a fever, menstruation, emotional stress, or suppression of the immune system. An episode of cold sores can develop following physical trauma, such as a dental procedure or overexposure of the lips to sunlight. Often the trigger is unknown.
Symptoms and Complications
The first oral infection with HSV usually causes sores inside the mouth (herpetic gingivostomatitis). In addition, the person generally feels sick and has fever, headache, and body aches. The mouth sores last 10 to 14 days and are often very severe, making eating and drinking extremely uncomfortable. In some first oral infections, swollen gums are the only symptom; occasionally, no symptoms develop. Herpetic gingivostomatitis most commonly develops in children.
Recurrences of oral HSV infection produce what are called "cold sores" (so named because they are often triggered by colds). These sores typically develop on the lips. An episode of cold sores begins with tingling at the site, lasting from minutes to a few hours, followed by redness and swelling. Usually, fluid-filled blisters form and break open, leaving sores. The sores quickly form into a scab. After a week, the scab falls off and the episode ends. Less frequently, tingling and redness occur without blister formation. Sometimes small clusters of herpes sores develop on the gums or the roof of the mouth; these sores also last about a week and then go away.
The first genital HSV infection can be severe and prolonged, with multiple painful blisters in the genital area. Fever and a general feeling of illness (malaise) are common, and some people have burning during urination. Occasionally, an infected person may have no symptoms. A recurring attack of genital herpes begins with symptoms (including local tingling, discomfort, itching, or aching in the groin) that precede the blisters by several hours to 2 to 3 days. Painful blisters surrounded by a reddish rim appear on the skin or mucous membranes of the genitals. The blisters quickly break open, leaving sores. Blisters also may appear on the thighs, buttocks, or around the anus. In women, genital blisters may develop on the vulva, in which case they are usually obvious and very painful. Internal blisters may develop in the vagina or on the cervix; they are less painful and are not visible. A typical episode of recurring genital herpes lasts a week.
In people with a weakened immune system, recurring outbreaks of genital or oral herpes can result in progressive, gradually enlarging sores that take weeks to heal. The infection may progress inside the body, moving down into the esophagus and lungs. Ulcers in the esophagus cause pain during swallowing, and infection of lungs produces pneumonia with cough and shortness of breath.
Sometimes HSV-1 or HSV-2 enters through a break in the skin of a finger, causing a swollen, painful, red fingertip (herpetic whitlow).
HSV-1 sometimes infects the cornea of the eye (herpes simplex keratitis (see Section 20, Chapter 230)). This produces a painful sore and blurred vision. Over time, the cornea can become cloudy, causing a significant loss of vision and requiring corneal transplantation.
Infants or adults with a skin condition called atopic eczema can develop a potentially fatal HSV infection in the area of skin that has the eczema (eczema herpeticum (see Section 18, Chapter 203)). Therefore, people with atopic eczema should avoid being near anyone with an active herpes infection.
Although it usually infects only the skin and outer surfaces of the body, HSV may rarely infect internal organs, such as the brain (herpes encephalitis). Herpes encephalitis begins with confusion, fever, and seizures and can be fatal.
Although an infrequent event, a pregnant woman can transmit HSV infection to her baby (neonatal herpes). Transmission usually occurs at birth, when the baby comes into contact with infected secretions in the birth canal. Infection of the baby is most likely when the woman has visible herpes sores in the vaginal area, although many babies become infected from mothers who have no apparent sores. Rarely, HSV can be transmitted to the fetus during pregnancy. Newborns with HSV infection become very ill. They may have widespread disease, brain infection, or skin infection. Without treatment, two thirds die, and even with treatment, many suffer brain damage.
Diagnosis
HSV infection is usually easy for a doctor to recognize. If the doctor is unsure, he may swab the sore and send the swab to the laboratory to grow and identify the virus. Sometimes doctors examine material scraped from the blisters under a microscope. Although the virus itself cannot be seen, scrapings sometimes contain enlarged infected cells (giant cells) that are characteristic of a viral infection. Blood tests to identify antibodies to HSV and biopsy of the sores can also be helpful. A new kind of blood test can distinguish between HSV-1 infection and HSV-2 infection.
Treatment
No current antiviral treatments can eradicate HSV infection, and treatment of the first oral or genital infection does not prevent chronic infection of nerves. However, treatment may relieve the discomfort of a recurring outbreak slightly and shorten its duration by a day or two. Treatment is most effective if started early, usually within a few hours of the start of symptoms--preferably at the first sign of tingling or discomfort, before blisters appear. In people who have frequent, painful attacks, the number of outbreaks can be reduced by continuous therapy (suppression) with antiviral drugs.
Penciclovir cream can shorten the healing time and duration of symptoms of a cold sore by about a day. Nonprescription creams containing docosanol or tetracaine may have a modest effect. Acyclovir, valacyclovir, or famciclovir taken by mouth for a few days may be the most effective treatment. Severe HSV infections are treated with intravenous acyclovir. People with herpes simplex keratitis are usually given trifluridine eye drops.
For people who have minimal discomfort, the only treatment needed for recurring herpes of the lips or genitals is to keep the infected area clean by gentle washing with soap and water. Application of ice may be soothing and reduce swelling.
Because herpes simplex is contagious, people with infection of the lips should avoid kissing during eruptions. People with genital herpes should use condoms at all times. Even when there are no visible blisters, the virus may be present on the genital surfaces and potentially transmissible to sex partners.
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