Influenza like illness monitoring in adults of the State Capitals and Federal District in Brazil by telephone survey.

OBJECTIVES In order to estimate the prevalence of influenza like illness (ILI) in adults from all state capitals and geographic regions in Brazil, a periodical monitoring of ILI cases by the national telephone survey (VIGITEL) was carried out in 2010. METHOD A cross-sectional study with 47,876 telephone interviews in the state capitals and Federal District, a probabilistic sample of adult population (>18 years-old) with landline telephone. Questions concerning the results of ILI cases and pandemic influenza (H1N1) 2009, from January 10 to November 30, were analyzed. The proportion of cases stratified by sociodemographic characteristics and Brazilian geographic region was weighted with data from the National Survey with Household Sampling (PNAD) 2008. RESULTS The prevalence of ILI cases in the last 30 days before interview was 31.2% (95%CI 30.2-32.2%) for all state capitals and the Federal District. This prevalence was higher among women, young adults (18 to 29 years-old) and individuals with 9 to 11 years of schooling. According to the geographic region analysis, Northern Brazil presented the highest prevalence of ILI cases. A tendency to increase with further decrease was observed among the geographic regions, except the Northeast. Need for health care assistance was reported by 26.8% (95%CI 25.1-28.5) from ILI cases. Among ILI cases that sought health care assistance, 2.6% (95%CI 1.8-3.4) reported pandemic influenza (H1N1) 2009 medical suspicion. CONCLUSION The results of this survey supported influenza surveillance as it provided timeliness and useful surveillance information, which were not captured by the traditional surveillance system, as the occurrence of ILI and need of health care assistance.