Chapter 13: Viral Infections of the Skin

INTRODUCTION TO CHAPTER

Despite all the advances in antiviral therapy and the body's efficient immune system, the viruses that cause common skin infections continue to evade complete destruction. The herpes simplex and herpes zoster virus can persist in a dormant state in the dorsal root ganglia. The viruses that cause verrucae vulgaris (common warts) and molluscum contagiosum can persist for months to several years in the epidermis.

Herpes simplex and herpes zoster infections can cause significant illness and death especially in immunocompromised patients if the infection spreads to other organs. Common nongenital warts and molluscum contagiosum rarely cause significant problems in immunocompetent patients, but for various reasons most patients want treatment for these conditions. Genital warts are often asymptomatic and may be clinically undetectable; however, patients with oncogenic wart virus infections are at increased risk for anogenital and oropharyngeal cancers.¹

HERPES SIMPLEX

Introduction

Table Key Points for Herpes Simplex

Herpes simplex viruses (HSV) cause primary, latent, and recurrent infections and they are common infections worldwide. Human herpes virus-1 (HSV-1) typically infects the oral cavity, lips, and perioral skin and is usually acquired in childhood via nonsexual contact. Human herpes virus-2 (HSV-2) primarily infects the genital area and is almost always acquired via sexual contact. Nevertheless, HSV-1 is becoming a more common cause of genital herpes infections¹. HSV has worldwide distribution but may be more common in less developed countries. Antibodies to HSV-1 are present in up to 85% of adults and antibodies to HSV-2 are present in 20–25% of adults.² However, many patients who have antibodies to HSV do not recall having had an infection.

Pathogenesis

HSV-1 and HSV-2 are human herpesviruses (HHV) which have double - stranded DNA and replicate within the nuclei of infected cells. HSV infects mucocutaneous tissue after direct contact or by way of secretions, mainly saliva in the case of HSV-1. The virus is transmitted via sensory nerves to the ganglia, where it may reside in a latent stage. Recurrent infections are caused by reactivation of the virus, which travels back to the skin or mucous membranes resulting in an active infection. Immune mechanisms suppress the virus with clearing of the lesions in 1–2 weeks, but latency in the ganglia persists. Recurrent mucocutaneous infection may occur every few weeks to months to years via viral reactivation. Viral shedding may continue after the infection has clinically resolved.

Clinical Presentation

History