Surveillance of Influenza-Like Diseases through a National Computer Network -- France, 1984-1989

In France, national surveillance of influenza-like syndromes has been continuous since November 1984 through the French Communicable Diseases Computer Network (FCDN). This report describes epidemics documented from 1984 to 1989 and emphasizes the 1988-89 epidemic.

FCDN was initiated under the joint auspices of the Institut National de la Sante et de la Recherche Medicale (comparable to the National Institutes of Health in the United States) and the Direction Generale de la Sante (the national department of health). FCDN uses electronic communications to facilitate collection, analysis, and redistribution of epidemiologic information about communicable diseases (1,2). Notifiable disease data collected by France's 96 regional departments of health are forwarded to the national department of health, analyzed, and redistributed to all users of the network through a weekly electronic bulletin.

FCDN collects epidemiologic data from general practitioners who volunteer to provide sentinel notification of epidemics. In November 1984, 50 sentinel general practitioners (SGPs) participated in FCDN; the number of participants has increased steadily and, since January 1988, has included 550, or approximately 1% of, French general practitioners. The SGPs were selected to be demographically representative of all general practitioners (i.e., by age, sex, geographic distribution, and type of practice). SGPs use terminals or personal computers with modems to report influenza-like syndromes and other selected conditions (e.g., measles, mumps, and viral hepatitis) to FCDN's host computer. SGPs can access the host computer 24 hours a day but must access the computer at least once a week--even if they have no cases to report. In particular, SGPs report the age, sex, and vaccination status of patients meeting the World Health Organization definition of influenza-like syndromes (i.e., a sudden fever of greater than 39 C, myalgia, and respiratory symptoms) (3). Estimates of the incidences of influenza-like syndromes are determined by geographic regions and redistributed on FCDN 4-10 days after the report of diagnosis.

From November 1984 through April 1989, a total of 89,705 cases of influenza-like syndromes were reported. In the 1984-85, 1985-86, and 1986-87 epidemics, increased activity began in the second half of December, peaked in early February, and ended by mid-April (Figure 1). During the respective three periods, maximal incidences were 12.7, 9.4, and 5.6 cases per 1000 residents. Although the 1987-88 epidemic began considerably later (late February), the maximal estimated incidence was comparable (5.8 cases per 1000).

In 1988-89, however, increased activity began in mid-November, peaked at 18.3 cases per 1000 residents during the second week of December, and ended in late January. In addition, the 1988-89 epidemic was characterized by a different distribution among age groups (Figure 1)--predominating in persons aged 0-17 years and affecting a smaller proportion of elderly persons than previous epidemics. Among persons aged 5-17 years, the peak incidence was 31.4 cases per 1000, compared with 2.4 cases per 1000 persons aged greater than or equal to 65 years. Thus, the 1988-89 epidemic occurred earlier, was of shorter duration, and affected primarily younger age groups while sparing the elderly.

From 1984 to 1989, the French Reference Centers on Influenza ("France Nord" and "France Sud") provided weekly results of viral isolates. For the 1984-85, 1985-86, and 1986-87 epidemics, most influenza isolates were A(H3N2) and A(H1N1) viruses. In 1987-88, influenza B virus was most frequently isolated. In 1988-89, influenza A(H1N1) predominated, although sporadic A(H3N2) activity occurred (4). Respiratory syncytial virus (RSV) was also isolated during each of the five periods. The predominance of illness reported in the 0-4-year age group (peak incidence: 23.5 cases per 1000 persons) may reflect RSV activity during the 1988-89 epidemic. Reported by: J Menares, Ph Garnerin, AJ Valleron, Unite de Recherches Biomathematiques et Biostatistiques de l'Institut National de la Sante et de la Recherche Medicale, Universite Paris 7, Paris. Influenza Br and Epidemiology Office, Div of Viral and Rickettsial Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note:

A major strength of the FCDN system for surveillance of infectious diseases is the rapidity of the collection, analysis, and distribution of data. The reports of influenza-like illness from SGPs, combined with information on virus isolations provided by the French Reference Centers, provide timely information for physicians who need to make decisions each year about both the administration of influenza vaccine and use of antiviral agents that are effective only against type A influenza viruses. Rapid diagnostic techniques to determine the type of influenza reported by the SGPs would further enhance the usefulness of this innovative system.

References

1. Valleron AJ, Bouvet E, Garnerin Ph, et al. A computer network for the surveillance of communicable disease: the French experiment. Am J Public Health 1986;76:1289-92.

2. World Health Organization. Communicable diseases: teleprocessing surveillance network. Wkly Epidemiol Rec 1986;61:369-76.

3. World Health Organization. Surveillance of acute viral respiratory infections in Europe--a report of WHO symposium, Madrid June 2-6, 1980. Copenhagen: World Health Organization Regional Office for Europe, 1981.

4. World Health Organization. Recommended composition of influenza virus vaccines for use in the 1989-1990 season: influenza activity, October 1988-February 1989. Wkly Epidemiol Rec 1989;64:53-6.

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