Finally, the work discussed here shows a potential effect of human movement between heterogeneous regions. As spatial effects are further studied in epidemic models, it remains to be seen how this phenomenon will extend to more complicated spatial geometries, including more patches and perhaps non-symmetric coupling terms. This work represents a first step towards understanding the role of migration and spatial heterogeneity in dynamical properties of dengue observed in epidemiological data, such as traveling waves of infection in Thailand (Cummings et al. 2004 ). Furthermore, because the migration-induced stabilization depends only on the existence of a Hopf bifurcation in the model, it is expected that the stabilization will be observed in other population models that also contain Hopf bifurcations (e.g., Fussmann et al. 2000; Greenhalgh et al. 2004) . Clinical factors associated with severity in hospitalized children infected with avian influenza (H5N1) OBJECTIVE: The World Health organization received reports of 478 laboratory-confirmed cases of influenza A (H5N1) from 15 countries between November 2003 and February 2010. More than 50% of these cases involved patients <20 years of age. Determining an association between the clinical factors at the time of hospital admission and prognosis may be useful for timely and adequate consultation and treatment. It has been difficult to obtain these clinical factors adjusted with other confounding factors, such as age and sex, as published studies of H5N1 virus infection usually reported only a few cases. So, we performed a pooled analysis of the reported cases. METHODS: Five case reports (36 patients <18 years of age) of H5N1 infection from four countries published between 2004 and 2009 were assessed based on available individual clinical data. Using the pooled data for all patients, we investigated the associations between patients’ prognosis and available laboratory findings, such as white blood cell (WBC) counts, platelet (PLT) counts, and serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) by adjusting for age and/or sex. RESULTS: The linear regression analysis revealed that mortality was negatively associated with WBC and PLT counts adjusted with age and sex. Increased log AST tended to be associated with a poor prognosis (p = 0.054), but there was no significant association between survival and log ALT level. CONCLUSIONS: Both decreased WBC and PLT counts can be considered to be common predictors of poor prognosis in H5N1 influenza patients <18 years of age. Further studies are needed for clarification. The 2009 H1N1 influenza pandemic spread throughout the world, but since the beginning of 2010, the number of cases of this influenza has been declining. Reports of avian influenza (H5N1) infection in humans have also been reported, raising the threat of a new pandemic through a novel combination of the H5N1 virus with the 2009 H1N1 strain.