A deviation bar chart for detecting dengue outbreaks in Puerto Rico

Objectives. A Centers for Disease Control and Prevention deviation bar char t (Statistical Software for Public Health Surveillance) and laboratory-base d surveillance data were evaluated for their utility in detecting dengue ou tbreaks in Fuel-to Rico. Methods. A significant increase in dengue incidence was defined as an exces s of suspected cases of more than 2 SDs beyond the mean for all 4-week peri ods from April through June (the period of lowest seasonal incidence), 1989 through 1993. An outbreak was defined as a cumulative annual rate of repor ted dengue greater than 3 per 1000 population. Results. Retrospective application of;he system to 1994 data showed agreeme nt with previous analyses. In 1995 and 1996, 36.4% and 27.3%, respectively, of municipalities with a significant increase in reports for 2 or more con secutive weeks before the first week of September had an outbreak, compared with 9.0% (in 1995, P = .042) and 6.0% (in 1996, P = .054) of towns withou t a significant increase. The system showed sensitivity near 40%, specifici ty near 89%, and accuracy in classifying municipalities near 84%. Conclusions. This method provides a statistically based, visually striking, specific, and timely signal for dengue control efforts.