Most of the viruses in this chapter cause skin lesions as their primary clinical manifestation. As described in Table 37–1, herpes simplex viruses 1 and 2 and varicella-zoster virus cause vesicles. Human herpesvirus 8 causes Kaposi’s sarcoma characterized by purple macular or nodular lesions. Smallpox virus causes pustules, but the virus has been eradicated, so these lesions are not seen in medical practice today. Molluscum contagiosum virus, a member of the poxvirus family, causes fleshy papules on the skin. Human papillomavirus causes papillomas (warts) on skin and mucous membranes of organs such as the cervix and larynx. Of the viruses described in this chapter, only two of the herpesviruses, cytomegalovirus and Epstein–Barr virus, do not cause skin lesions.
TABLE 37–1Features of Skin Lesions of Herpesviruses, Poxviruses, and Human Papillomavirus |Favorite Table|Download (.pdf) TABLE 37–1 Features of Skin Lesions of Herpesviruses, Poxviruses, and Human Papillomavirus
|Name of Virus ||Typical Skin Lesion |
|Herpes simplex virus type 1 ||Vesicle |
|Herpes simplex virus type 2 ||Vesicle |
|Varicella-zoster virus ||Vesicle |
|Cytomegalovirus ||None |
|Epstein–Barr virus ||None |
|Human herpesvirus 8 (Kaposi’s sarcoma virus) ||Flat or nodular purple lesion |
|Smallpox virus ||Pustule |
|Molluscum contagiosum virus ||Fleshy papule with umbilicated center |
|Human papillomavirus ||Papule with rough, irregular surface and spiny or cauliflower-like projections (papilloma, wart) |
All of the viruses in this chapter have DNA as their genome (Table 37–2). The herpesviruses and poxviruses have linear double-stranded DNA, whereas human papillomavirus has circular double-stranded DNA. Herpesviruses and human papillomavirus replicate in the nucleus of infected cells, whereas poxviruses replicate in the cytoplasm.
TABLE 37–2Properties of Herpesviruses, Poxviruses, and Human Papillomavirus |Favorite Table|Download (.pdf) TABLE 37–2 Properties of Herpesviruses, Poxviruses, and Human Papillomavirus
|Property ||Herpesviruses ||Poxviruses ||Human Papillomavirus |
|Virus family ||Herpesviruses ||Poxviruses ||Papillomaviruses |
|Genome ||Double-stranded DNA; linear ||Double-stranded DNA; linear ||Double-stranded DNA; circular |
|Virion DNA polymerase ||No ||No ||No |
|Virion RNA polymerase ||No ||Yes ||No |
|Nucleocapsid ||Icosahedral ||Complex ||Icosahedral |
|Envelope ||Yes ||Yes ||No |
The herpesvirus family contains six important human pathogens: herpes simplex virus types 1 and 2, varicella-zoster virus, cytomegalovirus, Epstein–Barr virus, and human herpesvirus 8 (also known as Kaposi’s sarcoma–associated herpesvirus).
All herpesviruses are structurally similar. Each has an icosahedral core surrounded by a lipoprotein envelope (Figure 37–1). The genome is linear double-stranded DNA. The virion does not contain a polymerase. They are large (120–200 nm in diameter), second in size only to poxviruses.
Herpes simplex virus (HSV)—electron micrograph. Three HSV virions are visible. Short arrow points to the envelope of an HSV virion. Long arrow points to the nucleocapsid of the virion. The dark area between the inner nucleocapsid and the outer envelope is the tegument. (Source: Dr. John Hierholzer, Public Health Image Library, Centers for Disease Control ...