Oliveira Carlos R, Costa Gisela S R, Paploski Igor A D, Kikuti Mariana, Kasper Amelia M, Silva Monaise M O, Tavares Aline S, Cruz Jaqueline S, Queiroz Tássia L, Lima Helena C A V, Calcagno Juan, Reis Mitermayer G, Weinberger Daniel M, Shapiro Eugene D, Ko Albert I, Ribeiro Guilherme S
Department of Pediatrics, School of Medicine, Yale University, New Haven, USA.
Centro de Pesquisas Gonçalo Moniz, Fundação Oswaldo Cruz, Ministério da Saúde, Rua Waldemar Falcão, 121, Candeal, 40296-710, Salvador, Brazil.
BMC Infect Dis. 2016 Mar 15;16:125. doi: 10.1186/s12879-016-1456-8.
Our understanding of the epidemiology of influenza is limited in tropical regions, which in turn has hampered identifying optimal region-specific policy to diminish disease burden. Influenza-like illness (ILI) is a clinical diagnosis that can be used as a surrogate for influenza. This study aimed to define the incidence and seasonality of ILI and to assess its association with climatic variables and school calendar in an urban community in the tropical region of Salvador, Brazil.
Between 2009 and 2013, we conducted enhanced community-based surveillance for acute febrile illnesses (AFI) among patients ≥ 5 years of age in a slum community emergency unit in Salvador, Brazil. ILI was defined as a measured temperature of ≥ 37.8 °C or reported fever in a patient with cough or sore throat for ≤ 7 days, and negative test results for dengue and leptospirosis. Seasonality was analyzed with a harmonic regression model. Negative binomial regression models were used to correlate ILI incidence with rainfall, temperature, relative humidity and the number of days per month that schools were in session while controlling for seasonality.
There were 2,651 (45.6% of 5,817 AFI patients) ILI cases with a mean annual incidence of 60 cases/1,000 population (95% CI 58-62). Risk of ILI was highest among 5-9 year olds with an annual incidence of 105 cases/1,000 population in 2009. ILI had a clear seasonal pattern with peaks between the 35-40th week of the year. ILI peaks were higher and earlier in 5-9 year olds compared with > 19 year olds. No association was seen between ILI and precipitation, relative humidity or temperature. There was a significant association between the incidence of ILI in children 5-9 years of age and number of scheduled school days per month.
We identified a significant burden of ILI with distinct seasonality in the Brazilian tropics and highest rates among young school-age children. Seasonal peaks of ILI in children 5-9 years of age were positively associated with the number of school days, indicating that children may play a role in the timing of seasonal influenza transmission.
我们对热带地区流感流行病学的了解有限，这反过来又阻碍了制定最佳的针对特定地区的政策以减轻疾病负担。流感样疾病（ILI）是一种临床诊断，可作为流感的替代指标。本研究旨在确定ILI的发病率和季节性，并评估其与巴西萨尔瓦多热带地区一个城市社区的气候变量和学校日历的关联。
2009年至2013年期间，我们在巴西萨尔瓦多一个贫民窟社区急诊室对5岁及以上患者进行了基于社区的急性发热性疾病（AFI）强化监测。ILI定义为测量体温≥37.8°C或报告有咳嗽或喉咙痛且发热≤7天的患者，同时登革热和钩端螺旋体病检测结果为阴性。采用调和回归模型分析季节性。使用负二项回归模型在控制季节性的同时，将ILI发病率与降雨量、温度、相对湿度以及每月学校上课天数相关联。
共有2651例ILI病例（占5817例AFI患者的45.6%），年平均发病率为60例/1000人口（95%CI 58 - 62）。2009年，5 - 9岁儿童的ILI风险最高，年发病率为105例/1000人口。ILI有明显的季节性模式，在一年的第35 - 40周达到高峰。与19岁以上人群相比，5 - 9岁儿童的ILI高峰更高且更早出现。未发现ILI与降水量、相对湿度或温度之间存在关联。5 - 9岁儿童的ILI发病率与每月预定上学天数之间存在显著关联。
我们发现巴西热带地区ILI负担较重，具有明显的季节性，且在低龄学龄儿童中发病率最高。5 - 9岁儿童ILI的季节性高峰与上学天数呈正相关，表明儿童可能在季节性流感传播时间方面发挥作用。
