Coronaviridae

A family of single-stranded RNA-containing viruses with 3 or 4 major antigens corresponding to each of the major viral proteins; some of which cause upper respiratory tract infections in humans similar to the “common cold”; others cause animal infections (infectious avian bronchitis, swine encephalitis, mouse hepatitis, neonatal calf diarrhea, and others). The viruses resemble myxoviruses except for the petal-shaped projections that give an impression of the solar corona. Virions are 120–160 nm in diameter, enveloped, and ether-sensitive. Nucleocapsids are thought to be of helical symmetry; they develop in cytoplasm and are enveloped by budding into cytoplasmic vesicles. Coronavirus and Torovirus are the only recognized genera. [L. corona, garland, crown]

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Co·ro·na·vi·ri·dae (kə-ro″nə-virґĭ-de) the coronaviruses and toroviruses: a family of RNA viruses having a pleomorphic virion 120–160 nm in diameter consisting of a lipid-containing membrane, with large peplomers, surrounding a helical (for coronaviruses) or tubular (for toroviruses) nucleocapsid. The genome consists of a single molecule of positive-sense single-stranded polyadenylated RNA (MW 5.5–6.1 Ч 10⁶, size about 30 kb for coronaviruses and 25–30 kb for toroviruses). Viruses contain three major structural polypeptides and are resistant to trypsin but sensitive to lipid solvents, detergents, ultraviolet radiation, disinfectants, and heat. Replicating occurs in the cytoplasm and assembly is by budding, usually through intracytoplasmic membranes; virions are released by exocytosis or by cell destruction. Transmission is mechanical, including airborne particles, contaminated equipment, and contact with infected persons. Included here are the genera Coronavirus and Torovirus.