About Herpes Simplex Virus

Herpes simplex is an acute vesicular eruption that is caused by the herpes simplex virus (HSV). Based on immunologic profiles, HSV has two types, type 1 and type 2. Traditionally, HSV-1 caused oral infections and HSV-2 genital infections, but there is significant overlap. Primary infection with either of these viruses is usually followed by recurrences (approximately 15% with HSV-1 and 60% with HSV-2). Each Recurrence occurs at the same location and, in the majority of patients, is preceded by a prodrome of itching and burning that starts approximately 24 hours prior to the outbreak.

Lesions erupt approximately one week after infection. The lesions of herpes simplex virus progress from indurated erythema to grouped vesicles that mature to pustules, which eventually rupture leaving a crust. Untreated, the course of primary infection is approximately three weeks. In primary infection, the mucous membranes can exhibit extensive areas of vesicles, usually gingivostomatitis or vulvovaginitis, but an outbreak can occur in any area of virus inoculation. In herpes recurrence, the lesions are grouped in the same location, and resolve in one to two weeks.

Less common location are herpetic whitlow, an infection of the finger that occurs in healthcare workers; herpes gladiatorum, an infection that occurs in wrestlers following traumatic inoculation of the skin. A generalized herpetic eruption in patients with existing atopic dermatitis is called eczema herpeticum. It is characterized by severe systemic symptoms.

Primary infection with HSV-1 usually occurs during childhood, with mot cases remaining asymptomatic. Approximately 10% of affected children develop acute gingivostomatitis (sores in the mouth). Infection with HSV-2 usually occurs after sexual contact. It can manifest as acute vulvovaginitis. Primary infection is typically associated with systemic symptoms, such as fever, myalgias, headache, and regional adenopathy. Lesions can be extremely painful, sometimes to the point of interfering with eating, drinking, or urination.

With what can herpes simplex be confused?

The differential diagnosis includes contact dermatitis, impetigo, and some fungal infections. These can be distinguished by history, gram stain and culture, patch testing for suspected allergens, KOH testing of a scraping, and Tzanck smear. Herpetic whitlow can be confused for paronychia, an infection of the cuticle.

How is herpes simplex diagnosed?

Herpes simplex is usually diagnosed clinically. The typical appearance is of grouped vesicles on an erythematous base. A recurrent lesion in the same location, preceded by a prodrome is highly suspicious for HSV. The diagnosis can be confirmed with a Tzanck smear preparation that reveals multinucleated giant cells, with viral culture, or with the Herpcheck enzyme immunoassay.

How is herpes simplex treated?

Antiviral drugs such as acyclovir (Zovirax), valacyclovir (Valtrex), famciclovir (Famvir), and penciclovir (Denavir) are used to treat HSV. Drugs are effective against actively replicating virus, but not on latent disease. Treatment may accelerate healing of lesions and reduce the period of viral shedding. Foscarnet is an alternative drug for acyclovir-resistant HSV. Frequent outbreaks can be suppressed with an oral antiviral.

What is the prognosis for herpes simplex?

For most patients, HSV remains dormant in the sensory ganglia, but some have recurrences, often attributed to factors such as stress, fever, menstrual period, or ultraviolet light. Recurrences are rarely inside the mouth. Chronic suppressive therapy with the drugs mentioned above can be useful in patients with frequent recurrences. Erythema multiforme is a rare complication of HSV. Immunocompromised patients, such as those with AIDS or HIV, can develop severe complications, including chronic ulcerative herpes simplex, which can last for months, and systemic infection involving other organs such as the central nervous system, liver, and lungs. Pregnant women can transmit the virus to newborns causing neonatal herpes, a devastating disease that is frequently fatal.

It is important to recognize that asymptomatic carriers can shed the virus and are an important reservoir of transmission.

Other herpes viruses

The viruses that causes herpes simplex are part of the herpesviridae family of viruses, which inlcudes 8 viruses known to causes disease in humans.  In addition to HSV-1 and HSV-2, described above, this includes varicella zoster virus (causes chicken pox and shingles), cytomegalovirus (CMV), epstein-barr virus (EBV), HHV-6 and HHV-7, which are implicated in roseola, and HHV-8, which is associate with Kaposi’s sarcoma and other disease.