Infants hospitalized for Bordetella pertussis infection commonly have respiratory viral coinfections

Background: Whether viral coinfections cause more severe disease than Bordetella pertussis (B. pertussis) alone remains unclear. We compared clinical disease severity and sought clinical and demographic differences between infants with B. pertussis infection alone and those with respiratory viral coinfections. We also analyzed how respiratory infections were distributed during the 2 years study. Methods: We enrolled 53 infants with pertussis younger than 180 days (median age 58 days, range 17-109 days, 64. 1% boys), hospitalized in the Pediatric Departments at "Sapienza" University Rome and Bambino Gesu Children's Hospital from August 2012 to November 2014. We tested in naso-pharyngeal washings B. pertussis and 14 respiratory viruses with real-time reverse-transcriptase-polymerase chain reaction. Clinical data were obtained from hospital records and demographic characteristics collected using a structured questionnaire. Results: 28/53 infants had B. pertussis alone and 25 viral coinfection: 10 human rhinovirus (9 alone and 1 in coinfection with parainfluenza virus), 3 human coronavirus, 2 respiratory syncytial virus. No differences were observed in clinical disease severity between infants with B. pertussis infection alone and those with coinfections. Infants with B. pertussis alone were younger than infants with coinfections, and less often breastfeed at admission. Conclusions: In this descriptive study, no associations between clinical severity and pertussis with or without co-infections were found.