HUMAN INFLUENZA-A H5N1 VIRUS-RELATED TO A HIGHLY PATHOGENIC AVIAN INFLUENZA-VIRUS

Background In May, 1997, a 3-year-old boy in Hong Kong was admitted to the hospital and subsequently died from influenza pneumonia, acute re spiratory 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 b e of the H5 subtype. Methods We carried out an antigenic and molecular comparison of the influenza A H5N1 virus isolated from the boy with o ne of the viruses isolated from outbreaks of avian influenza by haemag glutination-inhibition and neuraminidase-inhibition assays and nucleot ide sequence analysis. Findings Differences were observed in the antig enic reactivities of the viruses by the haemagglutination-inhibition a ssay, However, nucleotide sequence analysis of all gene segments revea led that the human virus A/Hong Kong/156/97 was genetically closely re lated to the avian A/chicken/Hong Kong/258/97. Interpretation Although direct contact between the sick child and affected chickens has not b een established, our results suggest transmission of the virus from in fected chickens to the child without intermediate mammalian host as a acting vessel''. This event illustrates the intensive global influenza surveillance.