For the case-investigation of H5N1 human infection reports containing individual clinical data, we selected five case reports from four countries published between 2004 and 2009 for investigation. From each report, we selected patients aged \18 years; ultimately, our study population consisted of 36 patients who were included in the pooled analysis. Four patients were from Tran et al. [7] (Vietnam), 12 were from Kawachi et al. [5] (Vietnam), 7 were from Chotpitayasunondh et al. [8] (Thailand), 8 were from Oner et al. [9] (Turkey), and 5 were from Kandun et al. [10] (Indonesia). H5N1 case-patients were identified by reverse transcriptase (RT)-PCR. The patients reported in Kawachi et al. [5] who showed severe ARDS were identified in the National Hospital of Pediatrics (NHP), and those in other reports were from passive surveillance. We investigated factors related with patients' prognosis from available laboratory findings, such as white blood cell (WBC) counts, platelet (PLT) counts, and serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT). The AST and ALT levels were not available for the cases of Kandun et al. [10] and five cases from Kawachi et al. [5] , and the leukocyte and platelet counts were not available for one case from Kawachi et al. [5] . Data were analyzed using Wilcoxon and Kruskal-Wallis tests for continuous variables and Fisher's exact test for categorical variables. Linear regression analysis was used for investigating associations between laboratory findings and patients' prognosis. All statistical analyses were done by SPSS ver. 14.0J (SPSS, Chicago, IL).