PROGRAM FOR THE SURVEILLANCE OF INFLUENZA IN PORTUGAL - RESULTS OF THE PERIOD 1990-1996

Objectives - To describe the situation of the influenza in Portugal th rough the estimates of the incidence rates and the identification of t he viral strains implicated on it during the period 1990-1996. Design - The integrated clinical and laboratory surveillance system for influ enza in Portugal is based on the Portuguese sentinel network. Influenz a cases are identified by general practitioners (GP) and notified to D ivision of Epidemiology (DEP) and to National Influenza Centre. Clinic al and epidemiological data based on the clinical diagnosis are record ed and incidence rates are computed for the whole country. Throat swab s and blood samples are taken from the patients with influenza and sen t to the National Influenza Centre to identify and classify the viral strains implicated. Participants - Lists of patients of the GPs collab orating on ''Medicos-Sentinela'' network. Results - In 1990-1991, 1992 -1993, and 1994-1995 there was a higher prevalence of influenza B viru s and the highest influenza activity occurred in February and March in contrast with 1991-1992, 1993-1994, and 1995-1996 where the highest n umbers of influenza cases occurred in November and December, and were associated with influenza A. Conclusions - During the past six years, 1990-1996, the influenza activity has been moderate in Portugal. From 1990-1996 influenza A and B viruses were prevalent every second year. The prevalence of influenza A was associated with the occurrence of th e highest number of influenza cases during December and January and th e prevalence of influenza B with the occurrence of the highest number of influenza cases during February and March.