A reactive mortality surveillance system in France for alert and decision-making

Abstract

Background In France, after the 2003 heat wave, a mortality syndromic surveillance system was set up by the National Public Health Agency, with objectives of early detection and reactive evaluation of the impact of expected and unexpected events to support decision makers. This study aims to describe the characteristics of the system and the main excess mortality period detected by the system since 2011 that led to alert decision makers for actions. Methods Anonymized data from the administrative part of death certificate were daily collected from 3042 computerized city halls and were transmitted to the agency in routine. Representativeness was measured as the proportion of death registered by the system among the exhaustive number of deaths and analyzed by age, month and region. Deaths were described by gender, age group at national and regional levels using proportion. Mortality surveillance is performed routinely based on the comparison of the weekly observed and expected number of deaths estimated with the model developed by the European consortium EuroMomo between 2012 and 2016. Based on criteria, when an excess of death is observed, decision makers are alerted and an investigation is launched. Results The system recorded 77.5% of the national mortality covering the whole territory and varying from 67% to 96.8% in metropolitan regions and overseas. Three major excess deaths episodes occurred during winters 2011–12, 2012–13 and 2014–15 and were highly correlated with flu epidemics periods. Five punctual excess periods were identified during the summer months, among them 4 were concomitant with a heat wave or elevated temperature period. No particular event was found correlated to the fifth excess. The system was also able to detect events such as an increase in mortality in Guadeloupe in 2014 concomitant with chikungunya epidemics. National and regional epidemiological mortality reports were published weekly (daily if required) and transmitted to the Ministry of Health and regional health authorities with potential recommendations. Conclusion The effectiveness of the reactive mortality surveillance system to alert decision makers has been demonstrated. It is useful to adapt along the event recommendation for control measures as well as evaluation of impact of the event on mortality. However, the absence of medical causes of death may limit the ability to target recommendations. Facing the challenge of emergence of epidemics and climate changes, this reactive mortality system will be complementary for other surveillance systems for the future health crisis. The development of mortality surveillance with causes of death will ensure more information for interpretation of all-cause mortality changes.