title: Clinical and virological factors associated with viremia in pandemic influenza A/H1N1/2009 virus infection.
abstract: BACKGROUND
  Positive detection of viral RNA in blood and other non-respiratory specimens occurs in severe human influenza A/H5N1 viral infection but is not known to occur commonly in seasonal human influenza infection. Recently, viral RNA was detected in the blood of patients suffering from severe pandemic influenza A/H1N1/2009 viral infection, although the significance of viremia had not been previously studied. Our study aims to explore the clinical and virological factors associated with pandemic influenza A/H1N1/2009 viremia and to determine its clinical significance.
  
  
  RESULTS
  Clinical data of patients admitted to hospitals in Hong Kong between May 2009 and April 2010 and tested positive for pandemic influenza A/H1N1/2009 was collected. Viral RNA was detected by reverse-transcription polymerase chain reactions (RT-PCR) targeting the matrix (M) and HA genes of pandemic influenza A/H1N1/2009 virus from the following specimens: nasopharyngeal aspirate (NPA), endotracheal aspirate (ETA), blood, stool and rectal swab. Stool and/ or rectal swab was obtained only if the patient complained of any gastrointestinal symptoms. A total of 139 patients were included in the study, with viral RNA being detected in the blood of 14 patients by RT-PCR. The occurrence of viremia was strongly associated with a severe clinical presentation and a higher mortality rate, although the latter association was not statistically significant. D222G/N quasispecies were observed in 90% of the blood samples.
  
  
  CONCLUSIONS
  Presence of pandemic influenza A/H1N1/2009 viremia is an indicator of disease severity and strongly associated with D222G/N mutation in the viral hemagglutinin protein.
authors: State Key Laboratory for Emerging Infectious Diseases, Carol Yu Centre for Infection, The University of Hong Kong, Hong Kong, China.
authors: Herman
authors: H
authors: Tse
authors: Kelvin K W
authors: KK
authors: To
authors: Xi
authors: X
authors: Wen
authors: Honglin
authors: H
authors: Chen
authors: Kwok-Hung
authors: KH
authors: Chan
authors: Hoi-Wah
authors: HW
authors: Tsoi
authors: Iris W S
authors: IW
authors: Li
authors: Kwok-Yung
authors: KY
authors: Yuen
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006389:Hemagglutinins, Viral / Q000378:metabolism; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000378:metabolism*; D007251:Influenza, Human / Q000821:virology*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D058873:Pandemics; D011110:Polymorphism, Genetic; D011379:Prognosis; D012367:RNA, Viral / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D014766:Viremia / Q000175:diagnosis* / Q000453:epidemiology*
chemical_list: D006389:Hemagglutinins, Viral; D012367:RNA, Viral