European Journal of Epidemiology

, Volume 14, Issue 3, pp 275–285

Influenza A and B epidemic criteria based on time-series analysis of health services surveillance data

  • Philippe Quénel
  • William Dab


Many countries now have epidemiological surveillance systems using health services-based indicators that allow detection of influenza epidemics. However, there is no accepted criterion for defining an influenza epidemic. An epidemic criterion has been developed, based on a time-series analysis of health services-based indicators collected on a weekly basis by a surveillance network implemented in the Paris region since 1984: the Groupe Régional d'Observation de la Grippe (GROG). For each new season, an epidemic threshold is independently defined for each health services-based indicator as the upper limit of the one-sided confidence interval of the expected value calculated from the weekly differences between the observed number of events and those predicted by a SARIMA model fitted on the non-epidemic data of previous seasons. Epidemic criteria for influenza A and B are then defined from the combination of both viral indicators and epidemic thresholds of individual health services-based indicators. Among health indicators, sick-leave data collected from GP's or the Health Insurance system, emergency home medical visits, and influenza-like-illness reported by GP's are the most sensitive indicators for the early recognition of epidemics. The exceeding of the above mentioned thresholds combined with virological data allows the specific detection of influenza A or B epidemics. This time-series method of analysing surveillance data provides early and reliable recognition of these epidemics.

Epidemics Health services-based indicators Influenza Public health surveillance Time-series analysis 


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  1. 1.
    MMWR. Influenza activity–United States, 1989–1991. MMWR 1991;40:809–810.Google Scholar
  2. 2.
    Housworth J, Langmuir AD. Excess mortality from epidemic influenza, 1957–1966. Am J Epidemiol 1974; 100: 40–48.Google Scholar
  3. 3.
    Jensen KE, Hogan RB. Laboratory diagnosis of Asian influenza. Public Health Rep 1958; 73: 140–144.Google Scholar
  4. 4.
    Thacker SB. The persistence of influenza A in human populations. Epidemiol Rev 1986; 8: 129–142.Google Scholar
  5. 5.
    Hope-Simpson RE. Epidemic mechanisms of type A influenza. J Hyg Camb 1979; 83: 11–26.Google Scholar
  6. 6.
    Stuart-Harris CH. Epidemiology of influenza in man. Br Med Bull 1979; 35: 3–8.Google Scholar
  7. 7.
    Thacker SB, Stroup DF. Persistence of influenza A by continuous close-contact transmission: The effect of non-random mixing. Int J Epidemiol 1990; 19: 1078–1082.Google Scholar
  8. 8.
    Neustadt RE, Fineberg HV, Califano JA. The swine flu affair. Decision-making on a slippery disease. Washington, United States Department of Health, Education, and Welfare, 1978.Google Scholar
  9. 9.
    Serfling RE. Methods for current statistical analysis of excess pneumonia-influenza deaths. Public Health Rep 1963; 78: 494–506.Google Scholar
  10. 10.
    Choi K, Thacker SB. An evaluation of influenza mortality surveillance 1962–1979. I. Time series forecasts of expected pneumonia and influenza deaths. Am J Epidemiol 1981; 113: 215–226.Google Scholar
  11. 11.
    Choi K, Thacker SB. An evaluation of influenza mortality surveillance, 1962–1979. II. Percentage of pneumonia and influenza deaths as an indicator of influenza activity. Am J Epidemiol 1981; 113: 227–235.Google Scholar
  12. 12.
    Perrotta DM, Decker M, Glezen WP. Acute respiratory disease hospitalizations as a measure of impact of epidemic influenza. Am J Epidemiol 1985; 122: 468–476.Google Scholar
  13. 13.
    Pachucki CT, Walsh Pappas SA, et al. Influenza A among hospital personnel and patients. Arch Intern Med 1989; 149: 77–80.Google Scholar
  14. 14.
    Buffington J, Chapman LE, Schmeltz LM, et al. Do family physicians make good sentinels for influenza ? Arch Fam Med 1993; 2: 859–864.Google Scholar
  15. 15.
    Hall CB, Douglas RG. Respiratory syncytial virus and influenza. Practical community surveillance. Am J Dis Child 1976; 130: 615–620.Google Scholar
  16. 16.
    Costagliola D, Flahault A, Galinec D, et al. A routine tool for detection and assessment of epidemics of influenza-like syndromes in France. Am J Public Health 1991; 81: 97–99.Google Scholar
  17. 17.
    Campbell DM, Paixao MT, Reid D. Influenza and the 'spotter' general practitioner. J R Col Gen Pract 1988; 38: 418–421.Google Scholar
  18. 18.
    Welliver RC, Cherry JD, Boyer KM, et al. Sales of nonprescription cold remedies: a unique method of influenza surveillance. Pediatr Res 1979; 13: 1015–1017.Google Scholar
  19. 19.
    Hannoun C, Dab W, Cohen JM. A new influenza surveillance system in France: The Ile-de-France GROG. I. Principles and methodology. Eur J Epidemiol 1989; 5: 285–293.Google Scholar
  20. 20.
    Dab W, Quénel P, Cohen JM, et al. A new influenza surveillance system in France: The Ile-de-France 'GROG'. II. Validity of indicators (1984–1989). Eur J Epidemiol 1991; 7: 579–587.Google Scholar
  21. 21.
    Quénel P, Dab W, Hannoun C, et al. Sensitivity, specificity and predictive values of health service based indicators for the surveillance of influenza A epidemics. Int J Epidemiol 1994; 23: 849–855.Google Scholar
  22. 22.
    SAS/ETS. User's Guide, Version 5 Edition, 1984.Google Scholar
  23. 23.
    Box GEP, Jenkins GM. Time series analysis: Forecasting and control. San Francisco: Holden Days, 1976.Google Scholar
  24. 24.
    Ljung GM, Box GEP. On a measure of lack of fit in time series models. Biometrika 1978; 65: 297–303.Google Scholar
  25. 25.
    Akaike H. On the likelihood of a time series model. Statistician 1978; 27: 215–235.Google Scholar
  26. 26.
    Choi K, Thacker SB. Improved accuracy and specificity of forecasting deaths attributed to pneumonia and influenza. J Infect Dis 1981; 144: 606–608.Google Scholar
  27. 27.
    Chatfield C, Prothero DL. Box-Jenkins seasonal forecasting: Problems in a case-study. J R Stat Soc 1973; 136: 295–336.Google Scholar
  28. 28.
    Quénel P, Dab W, Cohen JM, Hannoun C. Le groupe régional d'observation de la grippe en Ile-de-France: Cinq ans d'expérience. Santé Publ 1991; 6: 46–53.Google Scholar
  29. 29.
    Douglas RG. Prophylaxis and treatment of influenza. N Engl J Med 1990; 332: 443–450.Google Scholar

Copyright information

© Kluwer Academic Publishers 1998

Authors and Affiliations

  • Philippe Quénel
    • 1
  • William Dab
    • 2
  1. 1.Réseau National de Santé PubliqueCedexFrance
  2. 2.EDF-GDF, Service des études médicalesParisFrance

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