Coronaviridae: Spherical RNA viruses, in the order NIDOVIRALES, infecting a wide range of animals including humans. Transmission is by fecal-oral and respiratory routes. Mechanical transmission is also common. There are two genera: CORONAVIRUS and TOROVIRUS.Nidovirales: An order comprising three families of eukaryotic viruses possessing linear, nonsegmented, positive sense RNA genomes. The families are CORONAVIRIDAE; ARTERIVIRIDAE; and RONIVIRIDAE.Coronaviridae Infections: Virus diseases caused by CORONAVIRIDAE.SARS Virus: A species of CORONAVIRUS causing atypical respiratory disease (SEVERE ACUTE RESPIRATORY SYNDROME) in humans. The organism is believed to have first emerged in Guangdong Province, China, in 2002. The natural host is the Chinese horseshoe bat, RHINOLOPHUS sinicus.