Analysis of clinical records (Table 1) found that the mean duration from onset to death in those fatal human cases caused by Indonesian reassortant H5N1 viruses is 9.1 days (standard deviation [SD] = 3.9; n = 23) and those caused by other Indonesian H5N1 viruses is 7.7 days (SD = 2.7; n = 10), and their means are not significantly different (student t-test, p.0.25, two-tails). Therefore, based on the clinical records, the reassortant viruses did not kill human faster than other Indonesian H5N1 viruses did. However, we would recommend more experimental studies addressing the virulence, pathogenicity and immunogenicity of the reassortant viruses and the parent strains to verify this claim in the future.