title: Lower respiratory tract hemorrhage associated with 2009 pandemic influenza A (H1N1) virus infection.
abstract: Influenza-associated lower respiratory tract hemorrhage (LRTH) has been reported in previous pandemics and is a rare complication of seasonal influenza virus infection. We describe patients with LRTH associated with 2009 pandemic influenza A (H1N1) (pH1N1) virus infection identified from April 2009 to April 2010 in the United States.
  
  
  
  We ascertained patients with pH1N1-associated LRTH through state and local surveillance, the Emerging Infections Program, and CDCs Infectious Diseases Pathology Branch. All patients had influenza A, evidence of pneumonia, and evidence of LRTH.
  
  
  
  We identified 44 cases; the median number of days from illness onset to clinical signs of LRTH was one. Hemoptysis or respiratory tract bleeding was documented in 40% of pH1N1-associated LRTH cases, often present early during the course of illness. Twenty-one (48%) patients with LRTH had no other hemorrhagic diatheses. Seven (23%) patients with LRTH received antiviral treatment within two days of illness onset.
  
  
  
  During influenza season, clinicians should consider influenza infection in the differential diagnosis for patients presenting with hemoptysis or other signs or symptoms of LRTH. While the impact of timing of antiviral therapy on this complication has not been studied, the rapid progression of LRTH may support use of early empiric therapy. Continued investigation is necessary to betterdefine the clinical spectrum of both seasonal influenza- and pH1N1-associated LRTH.
authors.affiliation: Epidemiology and Prevention Branch, Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. EDKennedy@cdc.gov
authors.forename: Erin D
authors.initials: ED
authors.lastname: Kennedy
authors.forename: Monika
authors.initials: M
authors.lastname: Roy
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Norris
authors.forename: Alicia M
authors.initials: AM
authors.lastname: Fry
authors.forename: Mitul
authors.initials: M
authors.lastname: Kanzaria
authors.forename: Dianna M
authors.initials: DM
authors.lastname: Blau
authors.forename: Wun-Ju
authors.initials: WJ
authors.lastname: Shieh
authors.forename: Sherif R
authors.initials: SR
authors.lastname: Zaki
authors.forename: Kirsten
authors.initials: K
authors.lastname: Waller
authors.forename: Laurie
authors.initials: L
authors.lastname: Kamimoto
authors.forename: Lyn
authors.initials: L
authors.lastname: Finelli
authors.forename: Michael A
authors.initials: MA
authors.lastname: Jhung
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000998:Antiviral Agents / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D005260:Female; D006470:Hemorrhage / Q000188:drug therapy / Q000209:etiology*; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification* / Q000502:physiology; D007251:Influenza, Human / Q000150:complications* / Q000453:epidemiology / Q000821:virology; D008297:Male; D008875:Middle Aged; D058873:Pandemics; D012137:Respiratory System / Q000098:blood supply*; D012140:Respiratory Tract Diseases / Q000188:drug therapy / Q000209:etiology*; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology; D055815:Young Adult
chemical_list: D000998:Antiviral Agents
keywords: Hemorrhage; influenza; pH1N1; viral pneumonia