SURVEILLANCE OF INFLUENZA-LIKE ILLNESS IN FRANCE - THE EXAMPLE OF THE1995 1996 EPIDEMIC/

Study objectives-To discover if continuous computerised collection of morbidity data through a medical practice based sentinel network can b e used to monitor influenza-like illness (ILI) epidemics. To obtain ro ugh estimates of influenza vaccine effectiveness. Design-Continuous pa ssive surveillance of ILI through a computerised network of voluntary sentinel general practitioners (SGPs) in France (Sentinelle system). S etting-Five hundred SGPs practices. Participants-Since 1984, SGPs upda ted a database with information on eight communicable diseases includi ng ILI, via videotext terminals. Each ILI case is defined by the assoc iation of a sudden fever of 39 degrees C or above, respiratory symptom s, and myalgias. An ILI epidemic is detected when the national weekly incidence rate exceeds a seasonal threshold for two successive weeks. Main results-An ILI epidemic was reported from November 1995 to Januar y 1996. In total, 13 951 individual cases were reported by SGPs during the epidemic period. The size of the epidemic (number of patients con sulting a GP) was estimated to be 2 370 000 subjects. Maps of the epid emic showed that all regions have reported a high level ILI activity. The attack rate was the highest in school age children (13.5/100) and decreased as the age rose. Nearly 6% of the reported ILI cases among a dults and elderly were vaccinated. The flu vaccine effectiveness again st ILI was estimated to be 66% (95% CI 73%, 92%), ranging between 83% (95% CI 73%, 92%) among the subjects aged 15 to 24 years old to 16% (9 5% CI -12%, 44%) among the subjects aged 75 years or older. Conclusion s-The Sentinelle system demonstrated adequate sensitivity and timeline ss regarding ILI epidemic. Moreover, results of the monitoring were ma de available on the internet to increase the dissemination of informat ion. Also, estimates of influenza vaccine effectiveness have been easi ly obtained. Altogether, they represent key points for the control of crisis situation such as ILI epidemics or pandemics.