Analysis On Epidemic And Clinical Characters Of H1N1Influenza In Chongqing

Objective: To explore the epidemic and clinical characteristics ofH1N1influenza, by analyzing the data of diagnosed H1N1influenza casesin Chongqing from2009to2010, provide the scientific basis for preventionand control strategy.Methods: With descriptive epidemiological method, analysis on H1N1influenza cases rooted of report epidemic, outbreaks and influence likeillness from hospital of monitoring points, and clinical characteristics ofconfirmed H1N1influenza cases in Chongqing. Logistic-regression andmultivariate linear regression were used to evaluate related factors ofcomplications and period of fever.Results: From April2009to November2010,3239cases of H1N1fluwere reported in Chongqing (Incidence Ratio was11.51/100000),3patients died (Fatality Ratio was0.09%). The first case was on June13,2009, and the last one on March4,2010. Two time peaks of incidencecases in that period were respectively September1to September31andOctober11to November10. The top three areas of reported cases are respectively Yuzhong, Banan and Yongchuan district. Patients of10to20years old were67.74%, and most were students.32095ILI were monitoredby7hospitals, accounting for1.47%in out-patients. In7541specimens ofILI, the positive rate of isolated flu viruses was23.29%. Type of H1N1influenza was the advantage strain, accounting for51.08%in positivestrains. Between urban and rural monitoring stations points, the positivedetection rates were statistically significant differences.507gathered oroutbreak epidemic situations and8705cases were reported. The highincidence season of outbreak was at September and October in2009. Thefirst three areas with high outbreaks were Banan, Nnanan, Changshou andNanchuan district, and96.25%outbreaks were in school. Etiologymonitoring shows: H1N1flu outbreaks were accounting73.02%in the439outbreaks confirmed by the laboratory. The average age of2077cases ofH1N1influenza in Chongqing is15.41years old, while cases between6to18years of age accounted for76.02%. Male: Female=1.37:1. Vocationgave priority to students (primary and secondary school). Overweight andobesity cases respectively accounted for5.95%and0.89%.1.70%caseshad the history of basic chronic disease.4.53%cases had seasonalinfluenza vaccination history.2.99%cases had medicine for prevention.95.43%cases presented with fever, while the average temperature was38.68±0.62oC. The period with fever was between0-19days, withmedian of2days. In other18clinical symptoms, cases with cough, sore throat, headache, fatigue and runny symptoms accounted relatively higherpercentage.15.60%cases were hospital admissions, laboratory tests ofwhom main manifestation were decreased white blood cells andgranulocyte, increased of AST, CK, CK-MB, texture increase performanceand inflammation of their lungs.1.44%cases had complications，and allhappened in the hospital. The impact factors of complications includingBMI, basic chronic diseases, fever period, sore throat, cough duration andenlargement levels of amygdale. Treatment type and complications hadinfluenced on the length of period with fever.Conclusions: The key job of H1N1flu prevention and control shouldgive priority to students is Chongqing, and the monitoring system of ILIshould be continuous improvement. The clinical manifestations betweenInfluenza H1N1flu and ordinary seasonal flu were consistent. Differenttype of treatment process was the risk factor of fever period, but theemergence of complications was protective. Cases with obesity and basicchronic disease were high-risk groups of H1N1flu. Fever period, coughduration and enlargement levels of amygdale were risk factors ofcomplications. Sore throat had influenced the appearance of complications.