Molecular characterization of a nosocomial outbreak of human respiratory syncytial virus on an adult leukemia/lymphoma ward

Although nosocomial transmission of human respiratory syncytial virus (HRSV ) and its effect on morbidity and mortality among immunocompromised adults are well recognized, few studies have applied molecular techniques to diffe rentiate nosocomial from community-acquired infections. Between January and April 1997, an outbreak of HRSV occurred among adult patients in a leukemi a/lymphoma ward. Among 45 hospitalized patients undergoing bronchoscopy for investigation of acute respiratory illness, 8 were identified with HRSV in fection. One infected patient developed symptoms before admission and was t hought to be the index case. However, subsequent sequencing of 7 HRSV isola tes identified 2 distinct genotypes, GA5 (1 case) and GB3 (6 cases). The 6 GB3 isolates could be further differentiated into 2 strains with identical nucleotide sequences that differed from each other and from 14 community HR SV isolates. Instead of a single nosocomial outbreak of HRSV, multiple intr oductions of HRSV likely occurred with distinct lines of nosocomial transmi ssion.