A nomenclature for avian coronavirus isolates and the question of species status.

Currently, there is no agreed naming system for isolates of infectious bronchitis virus (IBV), whose host is the domestic fowl (Gallus gallus domesticus). A uniform, informative system for naming IBV isolates would be very helpful. Furthermore, the desirability of a single naming system has become more important with the recent discoveries that coronaviruses with genome organizations and gene sequences very similar to those of IBV have been isolated from turkeys (Meleagris gallopavo) and pheasants (Phasianus colchicus). To date, no genetic features have been found that are unique to turkey isolates and to pheasant isolates that would permit unequivocal differentiation from IBVs. Should the avian coronaviruses from turkeys, pheasants and other birds each be considered as distinct coronavirus species? Or should avian coronaviruses that have gene sequences similar to those of IBV be treated as host-range variants of IBV or, more objectively, as host-range variants of a species that might be called avian coronavirus (ACoV)? Clearly, the topic of avian coronavirus species differentiation requires debate. For the moment, a naming system for avian coronavirus isolates is overdue. Increasingly, papers will include data of coronaviruses isolated from more than one species of bird. It is desirable to have a nomenclature for avian coronaviruses that indicates the host species of origin. Furthermore, it would be helpful if the name of an isolate included the country/region of origin, an isolate number and the year of isolation. The names of avian paramyxovirus (APMV) and avian influenza virus (AIV) isolates have long since contained this information; I suggest that we adopt a similar convention for isolates of avian coronaviruses. For example, the D274 isolate of IBV could be named chicken/Netherlands/D274/78. Representatives of avian coronaviruses from turkey and pheasant would include turkey/United States(Nc)/NC95/95 and pheasant/UK/750/83. Two upper case letters would be used to denote country of isolation, whereas one upper and one lower case letter would be used to indicate state or province, e.g. Nc, North Carolina. The full-length names could be abbreviated, when desired, similar to the convention used for AIV isolates, e.g. chNL78, tyUS(Nc)95 and phUK83. If the serotype of an isolate has been clearly established, this might be included in the name at end, like the serotype designation of AIVs, e.g. chicken/China/NRZ/91 (Mass.) for the Chinese isolate of the Massachusetts serotype. This suggested naming system for isolates is essentially neutral with regard to whether viruses from different bird species should be considered as different coronavirus species or simply as variants of just one avian coronavirus species. In my opinion an informative nomenclature for avian coronavirus isolates is required now, to improve communication, and need not be delayed until a decision on the definition of coronavirus species has been made.