A space-time criterion for early detection of epidemics of influenza-like-illness.

OBJECTIVES

To develop a method based on a space-time criterion for early detection of epidemics of influenza-like-illness in France.

METHODS

Since 1984, the French Communicable Diseases computer Network (FCDN) routinely detects epidemics of influenza-like-illness when the national incidence rate is, for 2 consecutive weeks, above a threshold computed by a periodic regression model. It appears that some areas reported early increases in incidence several weeks before the national epidemic. An optimised space-time criterion allows an early detection of the epidemic periods.

RESULTS

Applying this space-time criterion to the last 11 epidemics (from 1986), the sensitivity was 0.82 and the specificity was 0.99.

CONCLUSION

This simple procedure can be used as an additional tool for early detection of an epidemic taking into account the distribution of new cases in space and time.