Sensitivity of Fever Sentinel Surveillance System to Survey Malaria Trends in Madagascar, 2014-2015

Fever sentinel surveillance system involving 34 health centers was set up in Madagascar to detect epidemicprone diseases in real time. Evaluative research was performed to assess the proportion of febrile cases that are not captured by sentinel sites. Capture-recapture method was used with two independent data sources: the first source was a passive detection of fevers in health centers while the second was an active screening of febrile subjects in the catchment area of each corresponding health center. Cases common to both sources were identified by matching name, age and location. Completeness of collected data was estimated through the population census. In 2014-15, six health centers were randomly selected from the sentinel network to perform the study. Active screening in the catchment areas of the six health centers detected 2,902 febrile illnesses among 149,835 inhabitants. Acute malaria represented 0.3% (10/2902) of febrile illnesses. The passive screening in health centers notified 157 cases of fever of which 7.6% (12/157) were acute malaria. The estimated number of febrile cases and acute malaria in the catchment areas based on the capture recapture analysis of data from the health facilities and the active screening was 3,829 [95% CI: 3,498-4,160] and 17 [95% CI: 7-27] respectively. The overall sensitivity of sentinel health centers to detect febrile illnesses and acute malaria was 4.1% and 70.0% respectively. Therefore most malaria cases were captured by the sentinel fever surveillance system. These results will serve as a baseline for future evaluative research of the fever sentinel surveillance system in Madagascar.