Using Breteau Index to analyze the nature of sporadic and outbreak cases of Dengue fever

Objective To understand the threshold of Breteau Index (BI) on Dengue fever outbreak in Guangzhou.Methods Dengue cases from Guangzhou during 2006 to 2012 in the National Infectious Disease Report and Management System were collected and described.Receiveroperating characteristic (ROC) curve was used to judge the threshold of BI on the outbreaks of Dengue fever.Results A total of 1 038 local cases were reported from 2006 to 2012 in Guangzhou city,with a total of 71 outbreaks and 259 sporadic episodes.Data from the ROC curve analysis showed that the highest Youden index that BI predicting Dengue fever outbreaks or sporadic were 6.4 and 9.5,respectively.When using BI=6.4 in predicting the sporadic case of Dengue,sensitivity and specificity were 67.8％,79.1％,respectively.When using BI=9.5 in predicting the outbreaks of Dengue,sensitivity and specificity were 81.7％,90.9％,respectively.Conclusion Both BI=5.0 and BI=9.5 showed effects on predicting the nature of sporadic or outbreak on Dengue,suggesting that the threshold need to be monitored,according to the purpose of control and availability of manpower,in order to get better sensitivity and specificity. Key words: Dengue fever;  Breteau index;  Threshold