title: An isolated outbreak of influenza A H1N1 in a haematological department during post-pandemic period.
abstract: OBJECTIVE
  Influenza A H1N1 virus strain was associated with the pandemic outbreak of febrile respiratory infections worldwide in 2009, however in August 2010, the WHO announced that the world had entered the postpandemic period. It offered specific recommendations for this period, including the identification of clusters of severe respiratory disorders and deaths. Here we report the fulminant course of influenza AH1N1 infection in the postpandemic period in a group of patients in a single hematology department. We make an attempt to identify potential risk factors and the mode of spreading, and to provide recommendations for best practice.
  
  
  METHODS
  We conducted a retrospective analysis of a cluster of patients diagnosed with or suspected of influenza A H1N1 infection in the period from December 2010 to March 2011.
  
  
  RESULTS
  Fourteen patients with hematological disorders unexpectedly developed acute respiratory failure ARDS (Acute Respiratory Distress Syndrome). Of them, nine tested positive for influenza A H1N1 in a screening test and eight in confirmatory polymerase chain reaction. The infection was fatal in nine patients, despite artificial ventilation in eight and oseltamivir administration in 11. Ten were in reverse isolation according to CDC. No similar cases occurred in the whole hospital concurrently, or in the hematology wards at any other time.
  
  
  CONCLUSIONS
  The occurrence of A H1N1 epidemics in a hematological ward in the post-pandemic period highlights the importance of awareness of this complication, prompt testing and antiviral treatment. Furthermore, it confirms the importance of vaccinating patients and personnel against influenza as a prophylactic measure.
authors.affiliation: Department of Haematology, Oncology and Internal Diseases, Medical University of Warsaw, Poland.
authors.forename: Joanna Ewa
authors.initials: JE
authors.lastname: Drozd-Sokołowska
authors.affiliation: Epidemiological Service, Central Clinical Hospital, Medical University of Warsaw, Poland.
authors.forename: Grażyna
authors.initials: G
authors.lastname: Dulny
authors.affiliation: Department of Haematology, Oncology and Internal Diseases, Medical University of Warsaw, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Waszczuk-Gajda
authors.affiliation: Department of Haematology, Oncology and Internal Diseases, Medical University of Warsaw, Poland.
authors.forename: Wiesław
authors.initials: W
authors.lastname: Wiktor-Jędrzejczak
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D005260:Female; D006748:Hospital Departments; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000175:diagnosis* / Q000453:epidemiology* / Q000401:mortality; D008297:Male; D008875:Middle Aged; D058873:Pandemics; D011044:Poland / Q000453:epidemiology; D012128:Respiratory Distress Syndrome / Q000175:diagnosis / Q000453:epidemiology; D012189:Retrospective Studies; D012307:Risk Factors; D055815:Young Adult