Why Large Viruses

A general perception is that viruses are very small, and, indeed, many of them approach the lowest limits at which viability appears sustainable. For example, a poliovirus particle consists of an 7.4-kb genome inside an 

These arguments apply only to viruses in which the particle size is genetically determined. In many helical viruses, the length of the capsid is indeterminate because it is defined by the size of the packaged nucleic acid molecule and therefore the same constraints do not apply. 

Herpesviruses are the most conservative, with all known members of the family having capsids of approximately the same size and with the same 

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