| BackgroudThe influenza is an acute respiratory infectious disease caused by influenza virus, as the first worldwide surveillance disease. Nanjing, as one of the most important surveillance influenza cooperation project cities in the province and even the country, now has a national influenza surveillance network laboratory (Laboratory of Nanjing Center for Disease Prevention and Control) and five national influenza surveillance sentinel hospitals (Jiangsu People’s Hospital, Nanjing Gulou Hospital, Nanjing Children’s Hospital, the First Hospital of Nanjing and the Second Affiliated Hospital of Nanjing Medical University). Due to the epidemic of influenza and avian influenza in the country, those have occured many times in Nanjing, the capital of Jiangsu Province, which has high population density and huge population mobility. Therefore, a long-term monitoring of influenza should be carried out to prevent and control the influenza epidemic in our city effectively.Objectives:(1) To understand the epidemiological characteristics of influenza and the variability of the predominant strains of influenza virus in Nanjing from 2006 to 2013.(2) To analyze the patterns and laws of influenza variation in Nanjing, for the short-term predicition of influenza cases by constructing a Autoregressive Integrated Moving Average (ARIMA) model.Methods:(1) The data of InfluenzaLike Illness (ILI) and aetiology was collected from Chinese Influenza Surveillance Information System of Chinese Disease Prevention and Control Information System.(2) ARIMA process of ETS module in SAS9.3 software was used to analyze monthly data of ILI cases during 2006 to 2013 to find the optimal model for forecasting ILI cases in 2014.Results:1. ILI and ILI% of Nanjing were respectively 5822.56 and 4.96%. There was no fluctuation in every year except September with the highest point and December with the lowest point.2. The influenza in Nanjing broke out in autumn and winter every year, and its peak was basically in January every year except 2009. ILI% in September and November had a substantial increasing compared with other months.3. The age distribution of ILI in five sentinel hospitals of Nanjing was consistent. The top three age groups were 0～,5～ and 25～. The maximum proportion of age group was 0～ and its average was 63.33%. The minimum was 60-in every year with and its average was 2.96%.4. From 2006 to 2013,20091 throat swab specimens was tested and 3370 influenza virus strains were isolated, cultured and identified in the influenza surveillance. The positive rate was 16.8% with maximum value,36.2%, in 2009and minimum value,8.3%, in 2013.5. Four models were constructed based on ARIMA (1,0,0) identified through the ILI and epidemic characteristics in Nanjing from 2006 to 2013.1. Model of diagnosed outpatients ILI proportion before breakout.2. Seasonal model of diagnosed outpatients ILI proportion before breakout 3. Model of breakout short-term effect of diagnosed outpatients ILI proportion.4. Model of breakout short-term and delayed effect of diagnosed outpatients ILI proportion. Comparing the prediction data and actual data finding average errors 33.62%, these models were proved to be precise for the prevention of infectious diseases.Conclusions1. According to the trend of ILI reported during 2006-2013 in Nanjing, the annual fastigium was in autumn and winter, and the peak was basically in January every year except 2009.2. During 2006～2013 in Nanjing, the top three age group were 0～,5～and 25～ consistent with results of other studies.3. According to the analysis of ILI% curve and influenza virus pathogen composition, ILI% level had nothing with the positive rate of the influenza virus but related with the etiology in each year. |
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