Outbreak of Nosocomial Respiratory Syncytial Virus Infections in a Hematology and Transplant Unit.

Abstract 3032

Respiratory syncytial virus (RSV) is a pathogen associated with bronchiolitis in infants and small children. However, immunocompromised adults might also be at risk for severe lower respiratory tract involvement induced by RSV. We report the rapid control of an outbreak of nosocomial RSV infections in an institution with special focus on allogeneic and autologous stem cell transplantations.

Between November 2011 and March 2012 56 patients were diagnosed with RSV infection by RT-PCR at our institution. In order to identify possible risk factors for lower respiratory tract involvement in RSV infected patients, clinical course of infection as well as radiological and laboratory findings were evaluated. Characterization of RSV strains in respiratory specimens was achieved by sequence analysis of part of the RSV glycoprotein G gene and phylogenetic comparison of outbreak and community strains was performed.

Out of 56 patients with RSV infection, 39 patients showed signs of lower respiratory tract involvement. 14 fatal outcomes were observed. In most of the lethal cases coinfections with other pathogens such as Aspergillus spp. or Pseudomonas aeruginosa were present. Therefore the exact impact of RSV on the fatal outcome remains difficult, if not impossible, to assess. Age, sex, underlying disease, disease control or transplant status did not differ significantly between severe and non-severe cases. However, hypogammaglobulinemia was associated with a higher risk for fatal infection (p = 0.03) in univariate analysis, whereas therapy with oral ribavirin might show a protective effect (p = 0.02). Prolonged viral shedding was frequently observed (median 22.5 [1 – 143] days), most pronounced in patients folllowing allogeneic transplantation (p = 0.04). The major mode of RSV transmission seemed to be direct patient-to-patient contact as suggested by evaluation of patient movements on the wards. Sequence analysis on respiratory specimens obtained from 46 patients revealed the presence of a particular outbreak strain in 40 patients, characterized by an identical nucleotide sequence of RSV GA2 subtype. Phylogenetic analysis showed low prevalence of the outbreak strain in the community. By implementation of rigorous isolation measures containment of outbreak was achieved.

Highly contagious viral pathogens such as RSV are able to cause rapidly spreading outbreaks among immunocompromised patients. Hypogammaglobulinemia might be a risk factor for severe lower respiratory tract infection. Treatment with oral ribavirin might have a positive effect on outcome. Rigorous isolation measures are essential to the containment of outbreak.