ABSTRACT
Human parainfluenza viruses (HPIVs) are members of the family Paramyxoviridae in the order Mononegavirales. Parainfluenza viruses are medium-sized enveloped virions that contain single-stranded, negative-sense, RNA genomes. HPIVs, of which there are currently four recognized viruses are members of the subfamily Paramyxovirinae, HPIV-1 and -3 are members of the genus Respirovirus and HPIV-2 and -4 are members of the genus Rubulavirus. HPIVs, like all members of the family Paramyxoviridae, contain nonsegmented, single-stranded ribonucleic acid genomes. The nucleocapsid protein ranges from 509 to 557 amino acids in length and is fairly conserved between HPIVs. The hemagglutinin-neuraminidase (HN) glycoprotein is the second glycoprotein found on the surface of HPIVs. HPIV replication begins with virus adsorption, viral/host membrane fusion, and cell entry. Cellular adsorption is initialized when the HPIV HN protein binds to sialic residues on the surface of the host cell. Many environmental factors can have an important influence on the survival of HPIVs, including temperature, humidity, pH, and the surrounding matrix.
