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.
Materials and 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.
© Georg Thieme Verlag KG Stuttgart ˙ New York.