Pneumoviridae (from Greek pneumo- 'lung' + -viridae 'virus', from Latin, 'poison, slimy liquid')[2] is a family of negative-strand RNA viruses in the order Mononegavirales.

[1] Pneumoviruses are pleomorphic, capable of producing spherical and filamentous, enveloped virions (virus particles) that vary in size from 150 to 200 nm in diameter.

The nucleocapsid consisting of a protein shell and viral nucleic acids has a helical symmetry.

Type I glycoprotein that facilitates fusion between the virus and the host cell membrane.

[7] Adds a methylated guanosine cap and poly(A) tail to nascent mRNA.

[1][4] First, the virus binds to HN glycoprotein receptors expressed on the surface of the cell.

[4] Then, through the action of the fusion protein, the virus fuses to the host plasma membrane and the nucleocapsid is released.

[4] Prior to undergoing replication, mRNA is transcribed and viral proteins are translated.

Transcription is dependent on virally encoded RNA-dependent-RNA-polymerase, which binds the genome at the 3' leader region and then sequentially transcribes each gene.

It is a negative-strand RNA virus that is the second most common cause of lower respiratory infection in young children.

Common symptoms include runny nose, congestion, sore throat, cough, headache, and fever, which can be seen as a cold.