We propose that novel influenza viruses emerge and evolve in multiple geographic localities and that the global evolution of influenza virus is complex and does not simply originate from a southern Chinese epicenter.
Although none of the participants in our study had virologically confirmed H7N9 infection, the high proportion of poultry workers with serologic evidence of H7N9 infection between May and December 2013 suggests a substantial risk of mild H7N9 infections in this group, supporting stricter control measures in live poultry markets.
BackgroundInfluenza has been associated with heavy burden of mortality and morbidity in subtropical regions. However, timely forecast of influenza epidemic in these regions has been hindered by unclear seasonality of influenza viruses. In this study, we developed a forecasting model by integrating multiple sentinel surveillance data to predict influenza epidemics in a subtropical city Shenzhen, China.MethodsDynamic linear models with the predictors of single or multiple surveillance data for influenza-like illness (ILI) were adopted to forecast influenza epidemics from 2006 to 2012 in Shenzhen. Temporal coherence of these surveillance data with laboratory-confirmed influenza cases was evaluated by wavelet analysis and only the coherent data streams were entered into the model. Timeliness, sensitivity and specificity of these models were also evaluated to compare their performance.ResultsBoth influenza virology data and ILI consultation rates in Shenzhen demonstrated a significant annual seasonal cycle (p<0.05) during the entire study period, with occasional deviations observed in some data streams. The forecasting models that combined multi-stream ILI surveillance data generally outperformed the models with single-stream ILI data, by providing more timely, sensitive and specific alerts.ConclusionsForecasting models that combine multiple sentinel surveillance data can be considered to generate timely alerts for influenza epidemics in subtropical regions like Shenzhen.
On December 29, 2011, a man infected with a subclade of the H5N1 virus was confirmed in Shenzhen, China. The clinical symptoms and immune factors of the patient were investigated and the phylogenetic and molecular characteristics of the virus were analyzed. High fever, rapid development of serious pneumonia and multi-organ failure were the main clinical symptoms. Arterial blood gas analysis showed that PaCO2 rose sharply and PO2 decreased. Leukocyte and platelet counts decreased rapidly. Peripheral blood lymphocyte counts indicated lymphopenia and inverted ratios of CD4(+) to CD8(+) cells. Cytokine analysis showed that the levels of serum IL-6, IL-10, and IFN-r continued to increase, whereas the levels of IL-12 and TNFs decreased during the clinical course. MCP-1 and IP-10 remained at a high level after infection. Phylogenetic analysis confirmed that the virus A/Shenzhen/1/2011 belongs to the new subclade 2.3.2.1. An Arg (R) insertion at P6 and an RP8I substitution in the HA cleavage site motif were detected in the virus. Compared to the vaccine strain, 16 specific substitutions occurred in the HA1 protein. Some of them were located on the receptor-binding site, glycosylation site and the region of the antigenic determinant. In summary, serious complications and immune system disorders were the main features of the infection with H5N1. Gene variation did not weaken the highly pathogenic features of viruses and the pathogenicity and antigenicity of the new subclade virus were changed.
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