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Herpes Simplex Virus Infections

Herpes is a member of the herpesvirus family, which includes varicella zoster virus, Epstein-Barr virus, and cytomegalovirus. Like all herpesviruses, herpes tends to establish latent infection and eventually it reactivates and becomes infectious. Most herpes-infected patients have asymptomatic infections or the symptoms are only mildly uncomfortable. However, a substantial number of patients experience frequent painful recurrences.

Virology and pathogenesis

Two types of herpes exist: herpes-1 and herpes-2.

herpes-1 may cause asymptomatic infection, oral lesions, nonoral or non-genital skin lesions, encephalitis, neonatal disease, and genital lesions

herpes-2 may cause asymptomatic infection, genital lesions, neonatal disease, nonoral, nongenital skin lesions, meningitis, and oral lesions

During epithelial cell infection, herpes infects the regional sensory or autonomic nerves, traveling via the nerve axon to the neuron, where it establishes a latent infection.

Transmission

herpes-1 and herpes-2 are transmitted from person to person through contact with infected skin lesions, mucous membranes, and secretions. The incubation period is 1 to 26 days.

Asymptomatic virus shedding may transmit the disease. Women who have had previous genital herpes-2 infection shed virus on 2%.

Oral/facial herpes infections

herpes-1 infection is extremely common in infants and children. The most common clinical manifestation of primary herpes-1 infection is gingivostomatitis, characterized by fever, malaise, myalgia, pharyngitis, irritability, and cervical adenopathy. The illness is self-limited and usually of short duration.

Recurrent herpes-1 infections are most frequently characterized by oral and lip lesions. Many individuals who have oral herpes lesions have no known history of prior gingivostomatitis.

herpes-2 also may cause oral lesions and pharyngitis, particularly in sexually active individuals.

Genital herpes infections

Many herpes infections are asymptomatic, but they can also cause papular, vesicular, or ulcerative lesions with pain, itching, urethral or vaginal discharge, and dysuria.

Primary infections cause more severe symptoms and signs, including extensive skin lesions, tender inguinal adenopathy, and extragenital lesions. Primary infections are often associated with fever, headache, malaise, abdominal pain.

Eighty percent of persons who have a first episode of herpes-2 genital infection will experience a recurrence in the first year.

herpes encephalitis

herpes encephalitis is the most common viral infection of the CNS. The incidence peaks at 5 to 30 years and at more than 50 years. Ninety five percent of cases are caused by herpes-1.

Neonatal herpes infections

Infection in neonates results from vertical transmission during the peripartum period in 85%; in utero or postpartum transmission rarely occurs. Seventy percent of untreated infants will progress to disseminated or CNS disease. Most neonatal infections are caused by herpes-2, although 30% of cases.

Skin, eye, mouth (SEM) disease accounts for 45% of peripartum infections.

SEM disease most commonly presents in the first or second weeks of life with vesicular skin lesions which may occur anywhere on the body.

Central nervous system disease is manifest as encephalitis, and it accounts for 35% of peripartum infections.

Neonatal herpes CNS disease most commonly presents in the second to third week of life. Only 60% will develop skin lesions during the illness. herpes CNS disease has a 50%.

Disseminated disease is characterized by hepatitis, pneumonitis, and disseminated intravascular coagulation, and it accounts for 20% of peripartum infections.