Performance of a syndromic system for influenza based on the activity of general practitioners, France.

BACKGROUND: In France, as in other industrialized countries, syndromic surveillance systems for the early detection of illnesses have proliferated, but few validation studies on these systems performances exist. In Bordeaux, a south-western city in France, a system using a network of general practitioners house calls, such as SOS Médecins, provided local health data used to guide health service response, in particular in case of flu-like pandemic. We explored the capacity of SOS Médecins system to identify and follow influenza outbreaks using data from the Sentinel network, considered as being a gold standard for tracking seasonal influenza in France. METHODS: Data from SOS Médecins were analysed and compared with data from the Sentinel network. The sensitivity and specificity of SOS Médecins system were evaluated for different simulated thresholds. RESULTS: A relationship between the number of visits for influenza from SOS Médecins and the number of influenza cases from the Sentinel network was observed; data from the two systems were highly correlated. We showed the capacity of SOS Médecins system to identify outbreaks with a sensitivity and specificity of 93%. CONCLUSION: The sensitivity and specificity of SOS Médecins for early outbreak detection showed the value of these data in monitoring influenza activity.

Validation of a syndromic surveillance system using a general practitioner house calls network, Bordeaux, France.

A new syndromic surveillance system has been developed in Bordeaux City, South West France, using a general practitioners' house calls network. Routinely collected, sociodemographic data, patients' complaints and medical diagnoses made at the end of the visit were monitored using syndrome groups such as influenza syndromes, bronchiolitis, gastrointestinal, respiratory syndromes and others, based on International Classification of Primary Care (ICPC)-2 codes. A process control chart was implemented in order to distinguish signals of interest from "background noise". In 2005 and 2006, a total of 303,936 visits were recorded. Seasonal epidemics of influenza-like illness, bronchiolitis or gastrointestinal were identified. The automated and real time nature of the system also allowed the early detection of unusual events such as an acute increase in the number of heat syndromes during the heat-wave that occurred in France in July 2006. This new system complements existing surveillance programs by assessing a large part of episodes of illness that do not require hospital admissions or the identification of an etiologic agent. Attributes and advantages of the system, such as timeliness and diagnostic specificity, demonstrated its utility and validity in term of syndromic surveillance purposes, and its extension at the national level is in process.