We have shown that EBOV particles are capable of a high degree of polyploidy, made possible by the extreme length polymorphism of budding virus particles. Polyploidy in filoviruses may be more extensive than in any other virus family, with 46% of virions having more than one genome copy, and some having up to 22 copies. Polyploidy has been shown to increase infectivity rates in paramyxovirus and birnavirus [2, 3] . Attempts to investigate infectivity rates of EBOV by centrifugal fractionation of the different sized particles are stymied by the extreme filamentous morphology, as well as that fact that EBOV of different lengths have the same buoyant density (personal observations). A complex double layered helical nucleocapsid appears to be unique to filoviruses. In the case of rhabdoviruses, the bullet-shaped nucleocapsid precludes them from being linked sequentially. Although some influenza strains can produce filamentous virions, this morphology appears to be driven by the matrix protein only [49] . A filamentous morphology may have evolutionary implications by allowing genome length flexibility. It could also enhance the ability for viral dissemination in infected tissues, for example by diapedesis of budding filamentous virions through epithelial layers.