Selection and Preliminary Characterization of Naturally Occurring Temperature—Sensitive Strains of Respir=ory Syncyfial Virus(RSV)

Seventeen naturally occurring B strains of RSV selected directly from 73 strains circulating in nature． The ts character was exam ined by parallel plaque assay and reexam ined three times for each strain．Based oi"1 the 33℃ ／39．5℃ 1gPFU difference，the RSV circulating strains could be divided into three groups of strain，namely．Our study suggested that there a more naturally 0e curring ts strains arnmag the subtype B RSV than am ng subtype A(P< 0．05)，and the proportion of ts strab~s of RSV in oatu re was appro ximately the e from l987 to 1992． Prelim inary experiments showed tha t the rmruraily occurring ts strains of RSV are genetically stable．