Coronaviruses are enveloped, positive-sense, single-stranded, ribonucleic acid viruses in the family Coronaviridae, of the order Nidovirales. An additional hemagglutinin esterase protein is encoded by a subset of coronaviruses and plays an important role for infection in the target host species, but is not required for viral replication. In June, 2012, a novel coronavirus was isolated from the sputum of a man in Jeddah, Saudi Arabia who presented with acute pneumonia and respiratory failure. An overactive host immune response has been associated with many of the diseases associated with coronavirus infections. The host interferon response is critical in limiting viral replication, and coronaviruses have developed multiple strategies to subvert interferon induction. Respiratory coronaviruses afford several options for therapeutic targets, including the S protein at viral attachment and entry; the nsp13 helicase, which functions during replication; and the 3C-like protease needed for viral proteolytic cleavage.