A family of pleomorphic, enveloped, non-segmented ssRNA viruses which infect man, animals or birds. One genus (Coronavirus) is currently recognized. Members include AVIAN INFECTIOUS BRONCHITIS virus (IBV; type species), human coronavirus (a causal agent of the COMMON COLD), murine hepatitis virus (MHV), porcine haemagglutinating encephalitis virus (see VOMITING AND WASTING DISEASE), and porcine TRANSMISSIBLE GASTROENTERITIS virus; probable members include e.g. coronavirus enteritis of turkeys virus (= turkey bluecomb disease virus), and neonatal calf diarrhoea coronavirus. ‘Possible members’ include feline infectious peritonitis virus (= feline coronavirus) and human enteric coronavirus (a possible causal agent of human FOOD POISONING).
Virion: ca. 75–160 nm diam., consisting of a helical nucleocapsid surrounded by the envelope; characteristic club-shaped glycoprotein projections (peplomers, ‘spikes’) 12–24 nm long extend from the outer surface of the envelope. Genome: positive-sense ssRNA, MWt typically ca. 6–7 ×106 (8 ×106 has been reported for IBV). The RNA is polyadenylated at the 3′ end. Proteins associated with the virion include (at least) S (‘spike’), M (membrane) and N (nucleocapsid). The virions are inactivated e.g. by lipid solvents and by detergents.
Virus replication occurs in the host cell cytoplasm. In IBV, 6 subgenomic mRNAs (A–F) are formed, all of which are 3′-coterminal with the genomic RNA (a so-called ‘nested set’ of mRNAs); each 5′ end has a common leader sequence (ca. 70 bases long) derived from the 5′ end of genomic RNA [possible mechanism: JGV (1986) 67 221–228]. (MHV forms a ‘nested set’ of 7 subgenomic mRNAs, designated RNA1–RNA7.) The virions mature by budding through the endoplasmic reticulum into vesicles.
[Molecular biology of coronaviruses: AVR (1983) 28 35–112.]
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(1968) : any of a family (Coronaviridae and esp. genus Coronavirus) of single-stranded RNA viruses that have a lipid envelope studded with club-shap