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Kenneth McIntosh, MD
Section Editor
Martin S Hirsch, MD
Deputy Editor
Anna R Thorner, MD


Coronaviruses are important human and animal pathogens. They are the cause of up to one-third of community-acquired upper respiratory tract infections in adults and probably also play a role in severe respiratory infections in both children and adults. In addition, it is possible that certain coronaviruses cause diarrhea in infants and children. Their role in central nervous system diseases, except for a single case report of encephalitis in a severely immunocompromised infant, has been suggested but not proven. (See 'Neurologic disease' below.)

The microbiology, epidemiology, clinical manifestations, diagnosis, treatment, and prevention of community-acquired coronaviruses will be discussed here. Severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) are reviewed separately. (See "Severe acute respiratory syndrome (SARS)" and "Middle East respiratory syndrome coronavirus: Virology, pathogenesis, and epidemiology".)


Coronaviruses are classified as a family within the Nidovirales order, viruses that replicate using a nested set of mRNAs ("nido-" for "nest"). The coronavirus subfamily is further classified into four genera: alpha, beta, gamma, and delta coronaviruses. The human coronaviruses (HCoVs) are in two of these genera: alpha coronaviruses (HCoV-229E and HCoV-NL63) and beta coronaviruses (HCoV-HKU1, HCoV-OC43, Middle East respiratory syndrome coronavirus [MERS-CoV], and the severe acute respiratory syndrome coronavirus [SARS-CoV]) (figure 1) [1,2].

Viral composition — Coronaviruses are medium-sized, enveloped, positive-stranded RNA viruses whose name derives from their characteristic crown-like appearance in electron micrographs (picture 1) [3,4]. These viruses have the largest known viral RNA genomes, with a length of 27 to 32 kb. The host-derived membrane is studded with glycoprotein spikes and surrounds the genome, which is encased in a nucleocapsid that is helical in its relaxed form but assumes a roughly spherical shape in the virus particle (figure 2). Replication of viral RNA occurs in the host cytoplasm by a unique mechanism in which RNA polymerase binds to a leader sequence and then detaches and reattaches at multiple locations, allowing for the production of a nested set of mRNA molecules with common 3' ends (figure 3).

The genome encodes four or five structural proteins, S, M, N, HE, and E. HCoV-229E, HCoV-NL63, and the SARS coronavirus possess four genes that encode the S, M, N, and E proteins, respectively, whereas HCoV-OC43 and HCoV-HKU1 also contain a fifth gene that encodes the HE protein [5].

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Literature review current through: Nov 2017. | This topic last updated: Jul 07, 2017.
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