Virus Morphology, Size, Structure, and Characteristics
Arboviruses from selected families or subgroupings that contain viruses of importance to humans or other vertebrates are compared in Table VIIL 10.2. Size varies considerably; shapes range from spherical to rhabdoform (bullet-shaped) to icosahedral.
Structurally, some entire groupings of viruses are enveloped, some are not. There are other differential characteristics, as indicated in the table. Again, the common bond is biological transmission by arthropod to vertebrate. How, in the evolution of viruses, this ability to exploit two phyla of living creatures arose again and again in such widely different taxa, is not known.Virus morphology is not totally explicated by reference to arboviruses subsumed in such groups as alphaviruses, Aaviviruses, bunyaviruses, rhabdovi- ruses, orbivirus (see Table VIIL 10.1). More detailed references (e.g., Theiler and Downs 1973; Field 1985) must be consulted for further information. Almost the entire grouping of arboviruses consists of RNA viruses that are readily degradable by lipid solvents, ribonucleases, or heat and freezing (at temperatures above — 70oC). The viral agents can be vacuum-desiccated satisfactorily, permitting greatly lengthened periods of storage with minimal loss in titer. Wet or desiccated material in glass-sealed ampoules can be stored in dry-ice containers or, better yet, in liquid nitrogen containers for long periods of time.