Published online 18 April 2009
Haematologica, Vol 94, Issue 6, 833-839 doi:10.3324/haematol.2008.003319
Copyright © 2009 by Ferrata Storti Foundation
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Original Article

Multicluster nosocomial outbreak of parainfluenza virus type 3 infection in a pediatric oncohematology unit: a phylogenetic study

Antonio Piralla1, Elena Percivalle1, Alessandra Di Cesare-Merlone2, Franco Locatelli2, Giuseppe Gerna1

1 Servizio di Virologia, Fondazione IRCCS Policlinico San Matteo
2 Oncoematologia Pediatrica, Fondazione IRCCS Policlinico San Matteo, Università degli Studi di Pavia, Pavia, Italy

Correspondence: Giuseppe Gerna, Director, Servizio di Virologia, Fondazione IRCCS Policlinico San Matteo, 27100 Pavia, Italy. E-mail:g.gerna{at}smatteo.pv.it

Background: Human parainfluenza virus type 3 (hPIV-3) has been reported to cause nosocomial outbreaks of respiratory infection, in particular among hematopoietic stem cell transplantation recipients.

Design and Methods: From September 2007 through January 2008 several episodes of hPIV-3 infection were observed among young patients followed at the Oncohematology Unit (OHU) or other units of the Pediatrics Department. In 32 young patients (median age 3.5 years, range 21 days–27 years), hPIV-3 infection was diagnosed by direct fluorescent antibody staining of cells from respiratory secretions, and virus quantified by real-time RT-PCR in nasopharyngeal aspirates or bronchoalveolar lavage samples. In addition, the epidemiologic relatedness of hPIV-3 strains was investigated by sequencing two variable regions of the hemagglutinin-neuraminidase gene (nt 1–569 and nt 762–1239).

Results: Of the 32 hPIV-3-positive patients, 19 were hematopoietic stem cell transplantation recipients, 8 had hematologic malignancies, and 5 were immunocompetent children. Sixteen patients had upper, and 16 lower respiratory tract infection. All patients but one had high viral load in nasopharyngeal aspirates (>1.0x106 RNA copies/mL). One patient died from respiratory failure with a high viral load in bronchoalveolar lavage. Phylogenetic analysis showed that 16/32 strains were identical. Besides this major cluster, three other clusters were identified, each one defining a smaller outbreak.

Conclusions: Phylogenetic analysis allows identification of the role of a single or multiple hPIV-3 strains in the person-to-person transmission within an outbreak occurring in clinical units.

Key words: nosocomial outbreak, human parainfluenza virus type 3, hematopoietic stem cell transplant recipients, phylogenetic analysis.