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1、Viral Infections and Global Change, First Edition. Edited by Sunit K. Singh. 2014 John Wiley Tyrrell etal., 1975). The 5 and 3ends of coronavirus (CoV) genomes contain short untranslated regions (UTRs). For the coding regions, the genome organization of all CoVs is similar, TABLE OF CONTENTS 21.1 In
2、troduction 393 21.2 Coronavirus classification and pathogenesis 397 21.3 Natural reservoirs and emergence of new coronaviruses 399 21.4 Alpha-, beta- and gamma coronaviruses: cross-species transmission 404 21.4.1 Alpha-coronaviruses cross-species transmission 404 21.4.2 Beta-coronaviruses cross-spec
3、ies transmission 405 21.4.3 Gamma-coronaviruses cross-species transmission 407 21.5 Anthropogenic factors and climate influence on coronavirus diversity and outbreaks 407 21.6 Conclusion 410 References 410 394 BIOLOGICAL ASPECTS OF THE INTERSPECIES TRANSMISSION OF SELECTED CORONAVIRUSES with the cha
4、racteristic gene order 5-replicase ORF1ab, spike (S), envelope (E), mem- brane (M) and nucleocapsid (N)-3, although variable numbers of additional ORFs are present in each subgroup of coronaviruses (Table 21.1). A transcription regulatory sequence (TRS) motif is present at the 3 end of the leader se
5、quence preceding most ORFs. Like other members of the Nidovirales order, CoVs produce a set of 3 nested tran- scripts with a common short leader sequence at the 5 terminus (Cavanagh, 1997; Gorbalenya etal., 2006; Spaan etal., 1988). Coronavirus (CoV) genetic diversity is maintained through accumulat
6、ion of point mutations in genes (genetic drift) due to low fidelity of the RNA-dependent RNA polymerase and homologous RNA recombination (genetic shift) (Domingo, 1998; Domingo etal., 1998a, b, 2006). Recombination is facilitated by a unique template switch- ing “copy-choice” mechanism during RNA re
7、plication with the transcription- regulating sequence (TRS) motifs believed to direct it (Lai, 1992; Lai etal., 1985). Additionally, because CoVs possess the largest RNA genomes, their capacity for accommodating gene rearrangements and modifications (sometimes significant: such as in the porcine res
8、piratory coronavirus (PRCV) spike gene deletion) is highest among all RNA viruses. This genetic plasticity allows CoVs to generate remarkable diversity in emergence of new strains and species and to adapt to new hosts and ecological niches without employing common biological vectors such as ticks, m
9、osquitoes etc. Utilization of mechanical vehicles is not well documented, but is less likely to play a major role in CoV spread due to CoV insta- bility in the environment (Sizun etal., 2000). An exception may be enhanced CoV stability when frozen permitting its increased transmission in winter. Fel
10、ine infectious peritonitis (FIP), first described in 1912 was presumably the earliest report of a CoV associated disease, whereas infectious bronchitis virus (IBV) was the first CoV isolated from chickens in 1937 (Beaudette and Hudson, 1937). This was followed by identification and characterization
11、of murine hepatitis virus (MHV) and other mammalian CoVs in 1940s (Cheever and Daniels etal., 1949; Doyle and Hutchings, 1946). Another two decades elapsed before CoV was recognized as the etiological agent of common colds in humans in 1965 (Hamre and Procknow, 1966; Tyrrell and Bynoe, 1966). Later
12、it was estimated that CoV infections contribute to as much as 35% of the total viral respiratory disease load during epidemics (Fielding, 2011). Overall, the proportion of adult colds caused by CoVs was estimated at 5% (McIntosh etal., 1970). Prior to the severe acute respiratory syndrome CoV (SARS-
13、CoV) emergence and global pandemic in 2002 2003, it was commonly accepted that in humans CoVs cause mainly mild upper respiratory tract infections (Fielding, 2011), with the exception of human enteric CoV (HECV-4408) isolated from a child with acute diarrhea (Zhang etal., 1994). In contrast, in anim
14、als, CoVs cause a wide spectrum of clinical conditions including respiratory, enteric, hepatic and neu- rological diseases, with clinical outcomes ranging from mild symptomatology to lethal. The SARS epidemic has substantially advanced CoV research efforts, especially studies of CoV biodiversity and
15、 genomics. Since the discovery of SARS-CoV, numerous novel animal CoVs have been identified and characterized revealing a remarkable diversity of animal CoVs. The SARS-CoV was postulated to be of animal origin, with horseshoe bats as a potential natural reservoir (Lau etal., 2005; Li etal., 2005a).
16、Besides SARS-CoV, bats are known to be reservoirs of important zoonotic viruses (including Ebola, Marburg, Nipah, Hendra, rabies and influenza) and viruses that can infect man or other animals (Calisher etal., 2006; Tong etal., 2012). Being abundant, diverse and geographically widespread, various species of bats, which are flying mammals equivalent to mosquitoes as insect vec- tors, were also recently shown to be natural hosts to a variety of CoVs (Calisher etal., 2006; Dominguez etal., 20
