NCIt definition : A genus of nonsegmented, negative-strand ssRNA viruses in the Pneumovirinae subfamily
that uniquely accomplishes cell fusion without the help of an attachment protein.
This virus has a genome of about 13 kb, encoding eight proteins. The virion is enveloped
and spherical with a diameter of about 150 nm;
Alternative definition : CDISC: Any viral organism that can be assigned to the genus Metapneumovirus.;