Introduction In Brazil, after influenza pandemic in 2009, influenza surveillance system was restricted to cases who sought healthcare assistance within severity signs and symptoms.
Objective To estimate the prevalence of influenza like illness (ILI) cases, ILI cases who sought healthcare assistance, with pandemic influenza H1N1 2009 (pH1N1) medical suspicion and oseltamivir prescription among the pH1N1 suspected cases by telephone survey.
Method In 2010, an influenza module of four questions was firstly included in the Telephone-based System for the Surveillance of Risk and Protective Factors for Chronic Diseases (Vigitel). In this study, data from January to November 2010 were analysed. The proportion of cases stratified by sociodemographic characteristics and Brazilian geographic region was weighted with data from the National Survey with Household Sampling, 2008.
Result The prevalence of ILI cases was 31.2% (95% CI 30.2% to 32.1%) in the period studied and it was higher among women, young adults (18–29 years of age) and individuals with higher education level. Northern Brazil presented the highest prevalence (36.8% of ILI cases; 95% CI 35.3 to 38.3%) of ILI cases. Need for healthcare assistance was reported by 26.8% (95% CI 25.1 to 28.5%) of ILI cases. Among ILI cases 2.5% (95% CI 1.8 to 3.4%) reported pandemic influenza H1N1 2009 (pH1N1) suspicion. Oseltamivir prescription was reported by 4.9% (95% CI 1.1 to 8.7%) pH1N1 suspected cases.
Conclusion The results of Vigitel supported the influenza surveillance in Brazil as it provided timeliness and useful information, which was not collected by the traditional surveillance system, based on sentinel units and severe acute respiratory infection notification.
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