TY - CHAP M1 - Book, Section TI - Viral Infections A1 - T. Desman, Garrett A1 - Cockerell, Clay J. A1 - Lyons, James J. A2 - Barnhill, Raymond L. A2 - Crowson, A. Neil A2 - Magro, Cynthia M. A2 - Piepkorn, Michael W. A2 - Kutzner, Heinz A2 - Desman, Garrett T. PY - 2020 T2 - Barnhill's Dermatopathology, 4e AB - Viruses are the most prevalent of all infectious agents and are also the smallest, ranging in size from 20 to 300 nm in diameter. The term “filterable agent” was used to refer to viruses before they could be visualized reliably because they pass through 0.22-µm filters that retain other organisms. All viruses are obligate intracellular parasites that depend on the host cell’s metabolism for replication. They are classified primarily by the nucleic acid content of their core (either DNA or RNA) because they contain only a single type of nucleic acid. They are also classified on the basis of the shape of their protein coat, or capsid, which is either spherical or cylindrical.1 Classification based on symptoms has proven useful to clinicians because certain viruses preferentially affect different organs, such as the skin, the nervous system, or the respiratory tract. Skin changes are often prominent manifestations of human viral infections, and the histopathologic changes associated with them vary from nonspecific features such as those seen in viral exanthemata to pathognomonic inclusion bodies in herpesvirus and cytomegalovirus (CMV) infections.1 SN - PB - McGraw Hill Education CY - New York, NY Y2 - 2024/11/14 UR - dermatology.mhmedical.com/content.aspx?aid=1178394626 ER -