Table 17.1.

Distinguishing Characteristics of Four Families of the Order Mononegavirales

Characteristic	Family Paramyxoviridae	Family Rhabdoviridaea	Family Filoviridae	Family Bornaviridae
Genome size (kb)	15–19	11–15	19	9
Virion morphology	Pleomorphic	Bullet-shaped	Filamentous	Spherical
Site of replication	Cytoplasm	Cytoplasm	Cytoplasm	Nucleus
Mode of transcription	Polar with non-overlapping signals (except pneumoviruses) and stepwise attenuation	Polar with non-overlapping signals and stepwise attenuation	Polar with non-overlapping signals and stepwise attenuation	Complex with mRNA splicing and overlapping start/stop signals
Host range	Vertebrates	Vertebrates	Humans, non-human primates and bats	Horses, sheep, cats, birds, (humans?) shrews and possibly other small mammals
Pathogenic potential	Mainly respiratory disease	Mild febrile to fatal neurological disease	Hemorrhagic fever	Immune-mediated neurological diseaseProventricular dilation syndrome in birds

^aVertebrate virus members.