HRSV is a member of the Pneumovirinae subfamily in the Paramyxoviridae family. It consists of a non-segmented, single-strand negative RNA genome packaged in a lipid envelope. The genome of HRSV is about 15.2 kb in length and encodes 10 genes and 11 proteins: NS1, NS2, N, P, M, SH, G, F, M2-1, M2-2, and L. The F protein and G protein are the major surface glycoproteins. Both of them can stimulate the production of neutralizing antibodies. The sequence of the F protein is highly conserved, while that of the G protein is hypervariable. Due to the genetic diversity in the G gene, sequence encoding the second hypervariable region in the C-terminal (HVR2) of the G protein has been used for genotyping of HRSV. According to the genetic characteristic and reactivity with monoclonal antibodies, HRSV is classified into 2 subgroups, A (HRSVA) and B (HRSVB). To date, there are 15 genotypes of HRSVA (GA1-GA7, SAA1, CB-A, NA1-4 and ON1-2), and 24 genotypes of HRSVB (GB1-GB4, SAB1-SAB4, URU1-2, BA1-12, GB5/CB1 and CBB).