Snapshot A 17-year-old patient presents to your clinic with a new rash. He is a wrestler on his high school varsity team. The rash is mildly itchy, but the patient denies any oozing or bleeding. On exam, you note umbilicated, waxy spots along his neck, arms, and waist in a nonspecific pattern. What are the characteristics of the most likely virus affecting this patient? DNA Virus Table Enveloped DNA Viruses Virus Disease Treatment Herpesvirus Herpesvirus Herpesvirus HSV type I Gingivosomastitis/herpes labialis (lip lesions) Keratoconjunctivitis Temporal lobe encephalitis Acyclovir HSV type II Genital vesicles Neonatal herpes Acyclovir Varicella zoster Chickenpox Shingles Acyclovir Epstein-Barr Infectious mononucleosis Burkitt lymphoma Nasopharyngeal carcinoma Treat symptoms Cytomegalovirus Mononucleosis Cytomegalic inclusion disease Pneumonia Ganciclovir HHV Type 6 Roseola (fevers, seizures, rash) Treat symptoms HHV Type 8 Kaposi's sarcoma None Herpesvirus Hepadnavirus Herpesvirus Hepatitis B Hepatitis IFN Lamivudine Poxvirus Poxvirus Poxvirus Variola Smallpox No known treatment (30% mortality) Molluscum contagiosum Molluscum contagiosum (wart-like benign tumors) Self-limiting Ritonavir Non-Enveloped DNA Viruses Virus Disease Treatment Adenovirus Adenovirus Adenovirus Adenovirus Acute respiratory disease Pharyngoconjunctivitis Epidemic keratoconjunctivitis Gastroenteritis (pediatric) Self-limiting Papillomavirus Papillomavirus Papillomavirus Human papilloma virus Warts Cervical intraepithelial neoplasia Treat with cryotherapy Polyomavirus Polyomavirus Polyomavirus JC virus Progressive multifocal leukoencephalopathy (PML) Supportive Parvovirus Parvovirus Parvovirus Parvovirus B19 Erythema infectiosum Aplastic crisis (in sickle cell) Hydrops fetalis Self-limiting or immunoglobulin for aplastic crisis Introduction to Viruses Viruses are obligate intracellular infectious agents with the following basic components DNA or RNA never both capsid a protein coat that surrounds the genetic material icosahedral or helical symmetry made of capsomers polypeptide chains organized into a globular subunit in helical symmetry, capsomers are bound to RNA and coiled forms a helical nucleoprotein capsid sometimes an envelope Viruses are classified by nucleic acid DNA or RNA double stranded or single stranded (+) positive or (-) negative stranded RNA single or segmented pieces of nucleic acid complexity of genome capsid icosahedral or helical envelope naked DNA or RNA + capsomers and other structural proteins = nucleocapsid (no host membrane) enveloped nucleocapsid + host membrane with viral-specified glycoproteins = enveloped virus size diameter or number of capsomers ploidy all viruses are haploid (1 copy of DNA or RNA) except retroviruses retroviruses have 2 identical copies of their ssRNA, approximating diploidy infectivity of purified nucleic acid purified nucleic acid that is intrinsically infectious dsDNA from most viruses except poxviridae except HBV (+) ssRNA from most viruses (+) linear, nonsegmented ssRNA can be translated immediately into a large protein by host machinery virus must carry protease to cleave the 1 large protein product that will be generated by the host machinery purified nucleic acid that is NOT intrinsically infectious (-) ssRNA viruses must carry an RNA-dependent RNA polymerase to generate mRNA the host machinery can read dsRNA they require enzymes contained in the complete virion for infectivity DNA Viruses Most DNA viruses are double-stranded (dsDNA, like human DNA) have icosahedral symmetry replicate in the nucleus are linear Exceptions parvoviridae only 1 strand of DNA (ssDNA) poxviridae no icosahedral symmetry surrounded by complex structural proteins replicates in cytoplasm papilloma, polyoma, and hepadna are non-linear (circular) Enveloped vs naked 3 DNA viruses are enveloped herpes hepadna pox the rest are naked The DNA viruses are "HHAPPPPy" herpes hepadna adeno pox polyoma papilloma parvo