title: [Frequency of polyphasic health-care-associated outbreaks is highest in surgical departments - results of a systematic literature search].
abstract: BACKGROUND
  So-called polyphasic nosocomial outbreaks describe a situation in which additional infections occur after a certain case-free interval - despite the detection of the outbreak's source. This article summarises the results of a systematic search of the medical literature on polyphasic outbreaks.
  
  
  METHODS
  For this purpose, the Outbreak Worldwide-Database, PubMed and reference lists of relevant articles were screened.
  
  
  RESULTS
  A total of 124 polyphasic outbreaks (median duration of 50 weeks) was included in the analysis and then compared to 2089 monophasic nosocomial outbreaks. Surgical departments were significantly more often involved in polyphasic outbreaks than they were in monophasic events (33.9 % vs. 24.5 %; p < 0.05). Hepatitis B virus outbreaks were significantly more often seen as poly-phasic events. Either there had been more than one source initially, or a new source developed during the first phase of the outbreak and led to additional cases thereafter.
  
  
  CONCLUSIONS
  Up to now, only little is known about polyphasic nosocomial outbreaks. Thus, there is a further need to close this gap of information in the future. Personnel on the ward as well as -infection control staff should always consider the possibility of the existence of more than one -source when investigating a nosocomial outbreak.
authors.affiliation: Medizinische Hochschule Hannover, Institut für Medizinische Mikrobiologie und Krankenhaushygiene, Hannover, Deutschland.
authors.forename: S
authors.initials: S
authors.lastname: Thon
authors.forename: K
authors.initials: K
authors.lastname: Graf
authors.forename: S
authors.initials: S
authors.lastname: Suerbaum
authors.forename: R-P
authors.initials: RP
authors.lastname: Vonberg
mesh_terms: D001424:Bacterial Infections / Q000453:epidemiology / Q000517:prevention & control / Q000635:transmission; D002353:Carrier State; D016358:Contact Tracing; D003428:Cross Infection / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission; D003431:Cross-Cultural Comparison; D003430:Cross-Sectional Studies; D004196:Disease Outbreaks / Q000517:prevention & control / Q000706:statistics & numerical data*; D006306:Health Surveys; D006509:Hepatitis B / Q000453:epidemiology; D006801:Humans; D009181:Mycoses / Q000453:epidemiology / Q000517:prevention & control / Q000635:transmission; D011785:Quality Assurance, Health Care; D012008:Recurrence; D012308:Risk Management; D013503:Surgery Department, Hospital / Q000706:statistics & numerical data*; D014777:Virus Diseases / Q000453:epidemiology / Q000517:prevention & control / Q000635:transmission