Family: Pneumoviridae

Genus: Metapneumovirus

Distinguishing features

Members of the genus Metapneumovirus  possess 8 genes. They lack the two promoter proximal NS1 and NS2 genes found in the members of the genus Orthopneumovirus. The gene order is N-P-M-F-M2-SH-G-L. Alignment of the L proteins of the metapneumoviruses shows a moderate level of conservation between the human and avian viruses. Their genome length is smaller than that of the members of the other genus. 

Virion

See discussion under family description. 

Genome organization and replication

See discussion under family description. 

Biology

See discussion under family description. 

Species demarcation criteria

Metapneumovirus species are distinguished on the basis of having an avian or human host. As noted, antigenic and sequence relatedness also distinguishes AMPV subgroups A, B, and D from HMPV; but AMPV subgroup C is more closely related to HMPV than to AMPV A, B, and D. Thus, antigenic and sequence relatedness do not consistently distinguish between HMPV and AMPV. The G attachment protein exhibits a high level of inter-strain diversity (up to 63% amino acid identity difference).