title: Human influenza A H5N1 virus related to a highly pathogenic avian influenza virus.
abstract: BACKGROUND
  In May, 1997, a 3-year-old boy in Hong Kong was admitted to the hospital and subsequently died from influenza pneumonia, acute respiratory distress syndrome, Reye's syndrome, multiorgan failure, and disseminated intravascular coagulation. An influenza A H5N1 virus was isolated from a tracheal aspirate of the boy. Preceding this incident, avian influenza outbreaks of high mortality were reported from three chicken farms in Hong Kong, and the virus involved was also found to be of the H5 subtype.
  
  
  METHODS
  We carried out an antigenic and molecular comparison of the influenza A H5N1 virus isolated from the boy with one of the viruses isolated from outbreaks of avian influenza by haemagglutination-inhibition and neuraminidase-inhibition assays and nucleotide sequence analysis.
  
  
  RESULTS
  Differences were observed in the antigenic reactivities of the viruses by the haemagglutination-inhibition assay. However, nucleotide sequence analysis of all gene segments revealed that the human virus A/Hong Kong/156/97 was genetically closely related to the avian A/chicken/Hong Kong/258/97.
  
  
  CONCLUSIONS
  Although direct contact between the sick child and affected chickens has not been established, our results suggest transmission of the virus from infected chickens to the child without another intermediate mammalian host acting as a "mixing vessel". This event illustrates the importance of intensive global influenza surveillance.
authors.affiliation: Department of Virology and WHO National Influenza Centre, Erasmus University, Rotterdam, The Netherlands. Claas@viro.fgg.eur.nl
authors.forename: E C
authors.initials: EC
authors.lastname: Claas
authors.forename: A D
authors.initials: AD
authors.lastname: Osterhaus
authors.forename: R
authors.initials: R
authors.lastname: van Beek
authors.forename: J C
authors.initials: JC
authors.lastname: De Jong
authors.forename: G F
authors.initials: GF
authors.lastname: Rimmelzwaan
authors.forename: D A
authors.initials: DA
authors.lastname: Senne
authors.forename: S
authors.initials: S
authors.lastname: Krauss
authors.forename: K F
authors.initials: KF
authors.lastname: Shortridge
authors.forename: R G
authors.initials: RG
authors.lastname: Webster
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002645:Chickens / Q000821:virology; D002675:Child, Preschool; D004196:Disease Outbreaks / Q000662:veterinary; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype; D009980:Influenza A virus / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity; D005585:Influenza in Birds / Q000453:epidemiology / Q000821:virology*; D007251:Influenza, Human / Q000453:epidemiology / Q000821:virology*; D008297:Male; D008969:Molecular Sequence Data