CONCISE COMMUNICATIONS 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 differentiate nosocomial from community-acquired infections. Between January and April 1997, an outbreak of HRSV occurred among adult patients in a leukemia/lymphoma ward. Among 45 hospitalized patients undergoing bronchoscopy for investigation of acute respiratory illness, 8 were identi®ed with HRSV infection. One infected patient developed symptoms before admission and was thought to be the index case. However, subsequent sequencing of 7 HRSV isolates identi®ed 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 HRSV isolates. Instead of a single nosocomial outbreak of HRSV, multiple in-troductions of HRSV likely occurred with distinct lines of nosocomial transmission. Human respiratory syncytial virus (HRSV) infection in adults typically results in a mild, self-limiting upper respiratory tract illness. However, adults with compromised immune sys