A comparative study on active and passive epidemiological surveillance for dengue in five countries of Latin America.

Background: Dengue is a notifiable infectious disease in many countries, but under-reporting of cases to National Epidemiological Surveillance Systems (NESSs) conceals the true extent of the disease burden. The incidence of dengue identified in a cohort study was compared with those reported to NESSs.

Methods: A randomized, placebo-controlled study was undertaken in Brazil, Colombia, Honduras, Mexico, and Puerto Rico to assess the efficacy of a tetravalent dengue vaccine (CYD-TDV) in children aged 9-16 years. The incidence of dengue in the placebo group was compared with that reported to NESSs in a similar age group (10-19 years) from June 2011 to April 2014.

Results: Three thousand six hundred and fifteen suspected dengue cases were identified in the study over 13527 person-years of observation. The overall incidence of confirmed dengue was 2.9 per 100 person-years (range 1.5 to 4.1 per 100 person-years). In the NESSs combined, over 3.2 million suspected dengue cases were reported during the same period, corresponding to over 1 billion person-years of observation. The incidence of confirmed dengue reported by the NESSs in the same locality where the study took place was 0.286 per 100 person-years across Brazil, Colombia, and Mexico (range 0.180 to 0.734 per 100 person-years). The incidence of confirmed dengue was 10.0-fold higher in the study than that reported to NESSs in the same localities (range 3.5- to 19.4-fold higher).

Conclusions: There is a substantial under-reporting of dengue in the NESSs. Understanding the level of under-reporting would allow more accurate estimates of the dengue burden in Latin America.