title: Epidemiology and clinical presentation of parainfluenza type 4 in children: a 3-year comparative study to parainfluenza types 1-3.
abstract: BACKGROUND
  Human parainfluenza viruses (HPIVs) are among the most common causes of respiratory tract infections in children. Little is known about the epidemiology and clinical presentation of HPIV type 4.
  
  
  METHODS
  A retrospective chart review and comparison of patients positive for HPIV types 1-4 by multiplex polymerase chain reaction between 2009 and 2012 at Children's Hospital Colorado was performed. Patients who had only direct fluorescent antibody testing performed or concurrent viral infections were excluded.
  
  
  RESULTS
  Of 11,533 samples, 752 (6.5%) were positive for HPIV. After exclusion criteria, 316 samples were included in the study. HPIV-4 had year-round prevalence with biennial peaks in odd-numbered years. HPIV-4 and HPIV-3 had similar clinical presentations. 50.8% and 51.5% of patients with HPIV-3-4 had hypoxia compared to 20.3% and 33.3% of patients with HPIV-1-2 (P < .01). HPIV-1 (23.6%) and HPIV-2 (24.2%) were more associated with stridor than HPIV-3 (6.6%) and HPIV-4 (0%) (P < .01). No patients with HPIV-4 had croup. Patients with HPIV-4 had similar lengths of stay and mortality as those with HPIV-1-3.
  
  
  CONCLUSIONS
  This is the first large-scale analysis of HPIV-4 clinical and epidemiologic features. HPIV-4 was most similar to HPIV-3 in clinical presentation. HPIV-4 had year-round prevalence with peaks in the autumn of odd-numbered years. HPIV-4 is a common respiratory pathogen capable of causing significant morbidity in children.
authors.affiliation: Department of Pediatrics, University of Colorado School of Medicine and Children's Hospital Colorado.
authors.forename: Holly M
authors.initials: HM
authors.lastname: Frost
authors.forename: Christine C
authors.initials: CC
authors.lastname: Robinson
authors.forename: Samuel R
authors.initials: SR
authors.lastname: Dominguez
mesh_terms: D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D029482:Parainfluenza Virus 4, Human; D012141:Respiratory Tract Infections / Q000453:epidemiology* / Q000821:virology*; D012189:Retrospective Studies; D019351:Rubulavirus Infections / Q000453:epidemiology* / Q000821:virology*
keywords: children; epidemiology; infection; parainfluenza virus; parainfluenza virus type 4; paramyxovirus; respiratory virus