布雷图指数、输入病例、气象因子与登革热本地流行的关系研究

Associations of Breteau index,imported cases,and meteorological factors with the risk of local epidemic of dengue fever

目的探讨布雷图指数（BI）、输入病例、气象因子与登革热本地病例发生与否和本地流行严重程度的关系，提出预警界值。方法选择广州市为研究现场，以2002—2013年为研究期限，以月为时间单元，分别选择登革热月本地病例发生与否和月本地感染病例发病数为结局变量，以月均BI、月均输入病例数、月均气温、月最高气温、月最低气温、月均日温差、月总和降雨量、月均降雨量、月均相对湿度和月均气压为自变量，应用分类和回归树（CART）模型对数据进行分析。结果2002—2013年期间共44个月（44/144，30.56%）发生本地感染疫情，共报告病例3 996例，包括3 769例（占94.32%）本地感染病例和227例（占5.68%）输入性病例。本地病例发生与否的分类树模型最终纳入月均输入病例数、月均BI、月最高气温和月最低气温，其中月均输入病例≥3.5例时本地病例发生风险最大，RR值为3.00（2.22～4.05）；月均输入病例＜3.5例、月均BI≥8.59时RR值为2.40（1.62～3.55）；月均输入病例〈3.5例、BI〈8.59、月最高气温≥31.41 ℃且月最低气温＜24.90 ℃时RR值为2.18（1.29～3.68）。本地流行严重程度的回归树模型最终纳入月均BI、月均气温和月均输入病例数，其中月均BI≥5.29且月均气温＜27.04 ℃时RR值最大，为5.11（3.36～7.77）；月均气温≥27.04 ℃且月均BI≥9.16时RR值为3.20（2.06～4.96 ），月均BI＜5.29且月均输入病例数≥3.5例时RR值为2.22（1.40～3.53）结论月均输入病例数和月均BI是本地病例发生与否的2个最重要因素，而月均BI和月均气温则是本地流行疫情严重程度的2个最重要因素。

ObjectiveTo explore the association of Breteau index（BI）, imported cases, and meteorological factors with local epidemic of dengue fever, so as to propose early warning thresholds.MethodsGuangzhou was selected as study site and years 2002-2013, as study period. The classification and regression trees model was applied to analyze the associations between the predictive variables including average monthly BI, average monthly imported cases, average monthly temperature,monthly maximum temperature,monthly minimum temperature,average monthly temperature difference,monthly total rainfall, average monthly rainfall,average monthly relative humidity, average monthly atmospheric pressure, and the outcome variables consisting of local dengue whether or not occur and the number of indigenous cases at month level separately.ResultsA total of 3 996dengue cases, including 3 769 （94.32%） indigenous cases and 227 （5.68%） imported cases, were reported in 44 （30.56% of 144） months during the period of 2002 - 2013. In the classification tree model for whether or not the local cases of dengue fever would appear, the number of imported cases, BI, maximum temperature and minimum temperature of the months were eventually incorporated. When the average monthly imported cases were ≥3.5, the RR was 3.00 （2.22 - 4.05） indicating the risk for local cases to occur was the greatest; when the average monthly imported cases were 〈3.5 and average monthly BI was ≥8.59, the RR was 2.40 （1.62 - 3.55）; when inputting the average monthly imported cases 〈3.5, average monthly BI 〈8.59, monthly maximum temperature ≥31.41 ℃, and monthly minimum temperature 〈24.90 ℃, the RR was 2.18 （1.29 - 3.68）. In the regression tree model for the severity of indigenous cases, average monthly BI, average monthly temperature, and average monthly imported cases were incorporated. When the average monthly BI was ≥5.29 and average monthly temperature was 〈27.04 ℃, the RR was the highest （5.11,3.36 - 7.77） ; when the average monthly temperature was ≥27.04 ℃ and everage monthly BI was ≥9.16, the RR was 3.20 （2.06 - 4.96）; when the average monthly BI was 〈5.29 and the average monthly imported cases were ≥3.5, the RR was 2.22 （1.40 - 3.53）.ConclusionThe everage monthly imported cases and everage monthly BI are most important two factors for whether or not local dengue cases would appear, and the average monthly BI and monthly average temperature, most important two factors for the severity of local dengue epidemic.