Chapter I 

 Animal Viruses: A Comparative Survey 



F. M. Burnet 



Walter and Eliza Hall Institute, Melbourne 



I. Definition of Animal Viruses 1 



II. A Basis for the Classification of Animal Viruses 3 



A. Psittacosis Group 3 



B. Poxvirus 4 



C. Herpesvirus 5 



D. Myxovirus 5 



E. Adenoviruses 5 



F. Arborviruses 6 



G. Enteroviruses 6 



H. Other Groups 7 



III. The Comparative Picture 7 



IV. Evolution of the Animal Viruses 10 



V. Is There Any Functional Unity among the Animal Viruses? 11 



References 14 



Under the name of animal viruses, we are compelled to include what is 

 manifestly a heterogeneous collection of agents. This makes it extremely 

 difficult to provide a comprehensive general picture of the process of virus 

 infection in mammalian and avian hosts. It seemed desirable, therefore, to 

 begin the present volume with an introductory chapter which would allow 

 some consideration of the main functional types of virus from a comparative 

 viewpoint. Most of the points to be mentioned are based on factual material 

 presented in later chapters, but investigation of some important groups of 

 viruses has been so limited that very little use of the results can be made in 

 attempts to analyze specific aspects of infection. In this chapter we are con- 

 cerned with defining the range of infectious agents covered by the term 

 animal viruses and with presenting a comparative survey of the main groups 

 with some necessary attention to classification and possible evolution. In 

 this way we can hope to supply a background against which the detailed 

 accounts of structural and functional attributes of animal viruses which 

 occupy the rest of this volume can be coordinated. 



I. Definition of Animal Viruses 



In attempting to define animal viruses, we immediately encounter char- 

 acteristically biological difficulties. From our point of view the most satis- 

 factory definition is probably the following: 

 vol. m. — 1 1 



