International Epidemic Intelligence at the Institut de Veille Sanitaire, France

The French Institute for Public Health Surveillance monitors health events of potential international importance occurring worldwide to provide timely warning to French health authorities. We reviewed the nature and place of occurrence of the last 200 events. From an individual country’s perspective, the need for multiple sources is emphasized.

L ocal epidemics may rapidly acquire international importance due to international travel and trade (1). With early warning, timely and adequate control measures can be adopted to prevent transmission. Epidemic intelligence is the systematic collection and collation of verifi ed and unverifi ed information from various sources, such as governments, United Nations organizations, nongovernmental organizations (NGOs), mass media, and personal communications (2). The Internet is transforming global disease surveillance (3). Information is selected by specifi c criteria, verifi ed (if informal), and thoroughly analyzed before communication to the public.
The Institut de Veille Sanitaire (InVS)-the French Institute for Public Health Surveillance-set up an epidemic intelligence unit to monitor outbreaks worldwide along the lines of the World Health Organization (WHO) Department of Epidemic and Pandemic Alert and Response. At the national level, this unit's legal mandate is to detect, verify, and rapidly assess information on potential international health threats, which may affect populations in France or French nationals worldwide. Its main task is to inform French authorities, public health professionals, and other partners of these epidemic risks and to place events with excessive media coverage in the proper perspective. Information is structured and widely communicated weekly through the electronic Bulletin Hebdomadaire International (BHI) (www.invs.sante.fr/international/index. htm). To better assess the type, characteristics, and location of alerts documented by the unit, we reviewed the health events posted in the BHI, i.e., all confi rmed information on potential international health threats that may affect populations in France or French nationals worldwide. We also examined initial signals and the use of various sources of international epidemic intelligence.

The Study
We reviewed 200 events posted in the 32 BHI from May 17, 2006 to December 27, 2006. We examined event topics, geographic location (country and world region), onset date of the fi rst case/outbreak, source, and publication date of the fi rst signal, delay between fi rst occurrence and the fi rst signal, signal type (passive email alert vs. active manual search) and alarm status (fi rst report vs. follow-up).
Potential sources were formal outbreak reports communicated by countries and supranational organizations (both offi cial and NGO) posted on the Internet and scientifi c online forums such as ProMED-mail (available from www.promedmail.org) (4-6). A dedicated tool was used to collect information available on the Internet: the Global Public Health Intelligence Network (GPHIN) (available from www.phac-aspc.gc.ca/media/nr-rp/2004/2004_gphin-rmispbk_e.html) is a software codeveloped by WHO and Health Canada. GPHIN is a secure, restricted-access early warning system that gathers media reports of public health signifi cance on a 24/7 basis (7). Like the medical intelligence system developed by the European community, the GPHIN is a multilingual system that provides relevant unverifi ed information on public health events by monitoring global media sources in 7 languages. This automated process includes a fi lter for relevancy, but specifi c email alerts and the categorizing of information must be complemented by human analysis.
The fi rst signal's source could be identifi ed in 88% (176/200) of events. News reports collected using the GPHIN were the most important initial sources of information, providing 36% (63/176) of all initial signals (online Appendix Table, available from www.cdc.gov/EID/ content/13/10/1590-appT.htm). Of these 63 events, 37 (59%) were automatically forwarded by the GPHIN e-alert system, and 26 (41%) were detected through active searches. Offi cial signals from the WHO network accounted for 29% (51/176) of all events posted in the BHI; ProMED-mail provided the fi rst signal for 17% of the events. Of 176 events included in the BHI, 20% (35/176) were fi rst detected only by manual and nonspecifi c Internet searches. Furthermore, 60% (105/176) of the posted events were fi rst detected through informal sources that required extensive verifi cation.
On average, delay between the fi rst case of an outbreak (including retrospectively) and the fi rst widely available signal was 3 months and 14 days (range 1 day-2 years, 10.5 months; n = 86). Among the 200 events posted, 107 were reported for the fi rst time. For these, mean delay between the fi rst case and the fi rst signal was 1 month and 23 days (range 1 day-5 months, 16 days; n = 63). Based on a small sample of alerts, the mean delay for alert messages provided by the GPHIN was shorter (1 month, 19 days; n = 19) than that of the ProMED-mail (2 months, 4 days; n = 6).

Conclusions
As in the 2006 WHO report (2), infl uenza A (H5N1) HPAI cases and cholera outbreaks were the major topics included in the BHI. Alerts posted for this period mainly concerned Asia due to the occurrence of infl uenza A (H5N1). Due to the specifi c economic and political situations of each country, availability and sensitivity of information sources differed. Multiple information sources somewhat compensated for these differences. Delays between the occurrence of events and fi rst reports refl ect the following: 1) interval between the occurrence of a fi rst case and development into a full-blown outbreak of international importance; 2) limitations of communicable disease surveillance, i.e., interval before an event is detected; 3) intrinsic limitations of epidemic intelligence, i.e., availability of information; and 4) the unavoidable prioritization of alerts, given time and resource constraints.
GPHIN was more effi cient than any other information source used in this analysis, including ProMED-mail, both in terms of number of signals and rapidity of signal availability after event occurrence. Signals from GPHIN, however, are unverifi ed media reports,and not all relevant events for our specifi c needs are electronically forwarded as e-alert. Permanent proactive searches using GPHIN or similar tools remain compulsory to address this limitation. Time-consuming human-operated screening of each report of the daily GPHIN list (500-2,000 reports/day) is needed as signal detection cannot be automated. Verifi cation processes are essential because reports of outbreaks are widely disseminated and easily accessible to the public (1).
WHO and other supranational organizations, such as the European Centre for Disease Prevention and Control, monitor health events of international importance. However, these organizations cannot completely meet all needs of individual countries. Our experience at a national institute shows that implementation of epidemic intelligence should be specifi cally tailored to effectively monitor the health of a country's population and translate directly into public health action. For example, in 2005, an extensive cholera outbreak was detected and documented in Senegal, with far-reaching implications for Franco-Senegalese pilgrims. Information posted in the BHI is used by physicians in French tropical disease departments and travel clinics, who can provide timely information to travelers, and target clinical examinations of those returning with suggestive symptoms. The operational suspect case defi nition for infl uenza A (H5N1) in returning travelers is continuously updated as foci appear in various areas. Information is also forwarded to the French Ministries of Health and Foreign Affairs to alert a larger segment of the population through institutional websites or warnings on airport billboards. This work was supported by the Institut de Veille Sanitaire, Saint-Maurice, France.
Dr Rotureau is an epidemiologist at the Tropical and International Department of the French Institut de Veille Sanitaire, Saint-Maurice, France. His research interests involve the study of ecologic, epidemiologic, and physiologic properties of Trypanosomatidae parasites and the diseases they cause.