2.1.2 Herpes Simplex

HSV infection is very common; about 50-90% of the adult population have evidence of previous infection.

Lesions on the skin arise from primary or secondary (re-activated) infection with the more common herpes simplex virus, Type 1 (H. labialis), or less frequently, Type 2 (H. genitalis). These DNA viruses are epidermotropic and neurotropic. Transmission is via contaminated surfaces or direct human to human contact. The incubation period is between 2-7 days.

Painful, grouped (herpetiform) vesicles on an erythematous base quickly evolve into erosions (less often into pustules) with local adenitis. Primary infections commonly affect the mouth (Herpetic gingivostomatitis), but also anogenital areas (Herpes genitalis, herpetic vulvovaginitis). Herpes neonatorum is rare. Recurrences mostly occur around the mouth (herpes simplex labialis, orofacial herpes, Type 1 HSV) or genitalis (Type 2). The eyes may also be affected (herpetic keratitis). Eczema herpeticum is a disseminated HSV infection due to impaired innate immunity because of barrier defects in those with atopic dermatitis. Recurrences usually occurs at the same site as the original lesion, possibly triggered by UV light, stress, hormonal changes or other factors.

Any part of the skin, intermediate epithelium or mucous membrane may be infected. The commonest sites include the lips, mouth, fingers, ano-genital skin and buttocks.

Tests are not usually required in typical orofacial herpes. Antigen test and Tzanck smear are no longer recommended. Nucleic Acid amplification tests (NAATs) (HSV DNA detection) is widely recommended in genital herpes (primary infection, genital ulceration) with typing HSV-1 /HSV-2. Serological tests (HSV-type specific serologies) are useless in most circumstances.

Although not usually required, histology may help to exclude other conditions. Balloon degeneration of keratinocytes in blister may be seen.

Impetigo, other sexually transmitted infections (STI) causing genital ulcers (syphilis, LGV), aphthous ulcers.

Therapeutic efficacy relies on prompt treatment. Options include topical agents such as astringents, antiseptics and antivirals. Systemic agents include antivirals (e.g. aciclovir or valaciclovir (500 mg / bid for 5 days). Treatment should be considered depending on symptomatology. Long-term prophylactic therapy can be helpful in those with frequent recurrence of disease.