  Morphologic diversity is observed across all families of viruses. Yet these
supra-molecular assemblies are produced most of the time in a spontaneous way
through complex molecular self-assembly scenarios. The modeling of these
phenomena remains a challenging problem within the emerging field of Physical
Virology. We present in this work a theoretical analysis aiming at highlighting
the particular role of configuration entropy in the control of viral particle
size distribution. Specializing this model to retroviruses like HIV-1, we
predict a new mechanism of entropic control of both RNA uptake into the viral
particle, and of the particle's size distribution. Evidence of this peculiar
behavior has been recently reported experimentally.
