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1、Downloaded from www.asmscience.org by IP: 129.110.242.50 On: Thu, 28 Feb 2019 23:09:38 1155 Coronaviruses KENNETH MCINTOSH AND J. S. M. PEIRIS 51 The fi rst coronavirus to be recovered was infectious bron- chitis virus (IBV) from chickens with respiratory disease, reported by Beaudette and Hudson in
2、 1937 (7). Another group of animal coronaviruses, the murine hepatitis viruses (MHV), was fi rst recognized by Cheever et al. (19) at the Rockefeller Institute in 1949 and independently by Gled- hill and Andrewes (37) in London, England, in 1951. Transmissible gastroenteritis in swine was fi rst rec
3、ognized in 1946 (24). These three important animal diseases were, however, considered unrelated until after the human co- ronaviruses (HCoVs) were discovered in the 1960s and the Coronavirus genus was defi ned. Tyrrell and Bynoe (128) described the fi rst HCoV, B814, recovered from a schoolboy with
4、a cold and passaged in organ cultures of human embryonic trachea. The virus, when examined by electron microscopy (EM) (3), was found to resemble avian IBV. At about the same time, Hamre and Procknow (44) recovered fi ve virus strains in tissue culture from medical students with colds. The pro- toty
5、pe strain HCoV 229E was examined by Almeida and Tyrrell (3), and its morphology was found to be identical to that of B814 and IBV. The organ culture technique was subsequently used to recover six further strains, including the prototype strain HCoV OC43, and three strains con- sidered antigenically
6、unrelated to either OC43 or 229E (84). In the winter of 20022003 an unusual and often lethal form of pneumonia appeared in Guangdong Province of China (150), a disease subsequently labeled severe acute respiratory syndrome (SARS). Within days of this disease spreading to Hong Kong in late February,
7、international air travel spread the virus far and wide, seeding outbreaks in Vietnam; Singapore; Toronto, Canada; and elsewhere. By the end of this brief but global epidemic in July 2003, 8,096 cases had been recorded, 744 of them fatal, in 29 countries across 5 continents. Spread within health care
8、 settings was a notable feature, accounting for 21% of all cases. The virus, termed the SARS coronavirus (SARS- CoV), initially emerged from an animal reservoir from live- animal markets in Guangdong, where diverse animal species are held and traded to serve the restaurant trade and the demand for e
9、xotic food. Within these markets, small mammals such as civet cats were found to harbor viruses closely related to SARS-CoV (39), and these mar- kets are the likely source for the initial interspecies trans- mission to humans. However, civet cats in the wild do not harbor these viruses (104) and thu
10、s were unlikely to be the natural reservoir of the virus. Recently, the precursor virus has been found in species of Rhinolophus bats (65, 70, 125). VIROLOGY Classifi cation Coronaviruses have been classifi ed as members of the order Nidovirales, positive-sense RNA viruses that replicate using a nes
11、ted (nido) set of mRNAs. The family Coronaviridae contains two genera, Torovirus and Coronavirus. The orig- inal basis for classifi cation of the coronaviruses into a sep- arate genus lay in the distinct morphology of the members (2) (Fig. 1). This classifi cation has been clearly justifi ed by the
12、unique chemical structure and strategy of replication. The Coronavirus genus is a large one, with representative viruses infecting multiple species, including chickens, tur- keys, ducks, geese, other birds, mice, cats, dogs, rabbits, cattle, bats, and humans. Many of the animal coronaviruses are of
13、great economic importance. On the basis of anti- genic relationships and genetic homologies, the coronavi- ruses were divided into three groups (Table 1). The fi rst contains HCoV 229E and several animal strains; the sec- ond contains OC43, MHV, and several other animal strains; and the third contai
14、ns IBV and several other avian coronaviruses. Several coronavirus species cause gastroenteritis in new- born or young animals, and it was therefore not surprising when coronavirus-like particles (CVLPs) were found by EM in human feces. The identity of CVLPs in human in- testinal contents and their r
15、ole in disease are, however, still matters of some controversy. All but a few strains have been detected only by EM of negatively stained prepara- tions of feces (18, 73, 80, 133). Their morphology is some- times different from that of other coronaviruses (74). On the other hand, several strains hav
16、e been propagated in intestinal organ cultures (16, 106), and both antigenic and biophysical studies have been performed on several isolates (34, 106). Certain strains have been found to be related both to calf diarrhea virus and to OC43 (34, 149). One strain, recovered from infants with outbreak-associated di- arrhea and originally isolated in fetal intestinal organ cul- Downloaded from www.asmscience.org by IP: 129.110.242.50 On: Thu, 28 Feb 2019 23:09:38 1156THE AGENTS. PART B. RNA VIRUSES F
