When a characteristic physical particle has been obtained, it should fulfill the following criteria before it is identified as a virus particle: 鉴定病毒颗粒需满足以下条件/标准：

1. The particle can be obtained only from infected cells or tissues.  

2. Particles obtained from various sources are identical regardless of the cellular origin in which the virus is grown.

3. Particles contain nucleic acid (DNA or RNA), the sequence of which is not the same as the species of host cells from which the particles were obtained.

4. The degree of infective activity of the preparation varies directly with the number of particles present.

5. Destruction of the physical particle by chemical or physical means is associated with a loss of viral activity.

6. Certain properties of the particles and infectivity must be shown to be identical (eg, their sedimentation behavior in the ultracentrifuge and their pH stability curves).

7. Antisera prepared against the infectious virus should react with the characteristic particle and vice versa. Direct observation of an unknown virus can be accomplished by electron microscopic examination of aggregate formation in a mixture of antisera and crude viral suspension.

8. The particles should be able to induce the characteristic disease in vivo (if such experiments are feasible).

9. Passage of the particles in tissue culture should result in the production of progeny with biologic and antigenic properties of the virus. 

以上转自：Jawetz, Melnick, & Adelberg’s Medical Microbiology （Twenty-Eighth Edition），CHAPTER 29