ðɪ ˌɛnˈɛs wˈʌn pɹˈoʊtiːn ʌvðə hˈaɪli pˌæθoʊdʒˈɛnɪk ˈeɪvɪən ˈeɪtʃ fˈaɪv ˈɛn wˈʌn vˈaɪɹəsᵻz sˈɜːkjʊlˌeɪɾɪŋ ɪn pˈoʊltɹi ænd wˈɔːɾɚfˌaʊl ɪn sˈaʊθiːst ˈeɪʒə ɪz kˈɜːɹəntli bᵻlˈiːvd təbi ɹᵻspˈɑːnsᵻbəl fɚðɪ ɛnhˈænst vˈɪɹələns ʌvðə stɹˈeɪn.
The NS1 protein of the highly pathogenic avian H5N1 viruses circulating in poultry and waterfowl in Southeast Asia is currently believed to be responsible for the enhanced virulence of the strain.