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They wondered If wheezeles Could turn Into measles, If sneazles Would turn Into mumps
—A.A. Milne, Now We Are Six
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The major viruses described in this chapter are mumps, measles, rubella, and the human parvovirus B19, which are from different virus families and genetically unrelated, but share several common epidemiologic and clinical characteristics, including: (1) worldwide distribution, with a high incidence of infection in nonimmune individuals; (2) humans as sole reservoir of infection; and (3) person-to-person spread primarily by the respiratory (aerosol) route.
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The other diseases discussed in this chapter are roseola infantum and rubella-like rashes caused by many different viruses that are mainly common illnesses occurring in early life. Key characteristics of these major viruses are summarized in Table 10–1.
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Enveloped, negative sense single-stranded RNA virus with hemagglutinating and neuraminidase activity (HN) and fusion protein F
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Mumps virus is a paramyxovirus, and only one major antigenic type is known. Like fellow members of its genus, it contains a single-stranded, negative-sense RNA genome, and a nucleocapsid that is surrounded by a matrix protein followed by a lipid bilayer envelope (see Figure 9–4). Two glycoproteins are on the surface of the envelope; one mediates hemagglutination and neuraminidase (HN) activity, and the other is responsible for viral lipid membrane fusion (F) to the host cell. Similar to other paramyxoviruses, mumps virus initiates infection by attachment of the HN spike to sialic acid on the cell surface, and F protein promotes fusion with the plasma membrane. It replicates in the cytoplasm by using its own RNA-dependent RNA polymerase, and the progeny viruses are released by budding from the cell membranes. Details ...