INTRODUCTION Influenza A and B viruses constantly evolve and cause seasonal epidemics and sporadic outbreaks. Therefore, epidemiological surveillance is critical for monitoring their circulation pattern. Trivalent and quadrivalent vaccine formulations are available in Panama (until and since 2016, respectively). Herein, we analysed influenza A and B epidemiological patterns in Panama. METHODS This was a retrospective descriptive analysis of all laboratory-confirmed influenza nasopharyngeal samples recorded between 2011 and 2017 in the nationwide surveillance database of Gorgas Memorial Institute for Health Studies. The analysis involved data relative to demographic information, virus type, subtype and lineage, geographic region, treatment and outcomes. The percentage level of mismatch between circulating and vaccine-recommended B lineage was assessed for each May-October influenza season. RESULTS Among 1839 influenza cases, 79.6% were type A and 20.4% were type B. Most of them were observed in Panama City (54.7%) followed by the West (23.2%) and Central (16.7%) regions; across all regions, influenza A and B cases were distributed in a 4:1 ratio. Overall, approximately half were hospitalized (52.0% for type A; 45.5% for type B) and 11 (0.6%) died. Treatment, usually antimicrobial, was administered in 15.1% of cases. Children less than 2 years old were the most affected by this disease. Influenza type A circulated every year, while influenza B only circulated in 2012, 2014 and 2017. In the 2012 May-October influenza B season, the predominant lineage was B/Victoria and a switch to B/Yamagata was observed in 2014. Both lineages co-circulated in 2017, leading to a 38.9% B-lineage-level vaccine mismatch. CONCLUSION Influenza A was predominant among all ages and children less than 2 years and inhabitants of Panama City reported the highest circulation rate. In 2017, co-circulation of both B lineages led to a vaccine mismatch. Continuous monitoring of seasonal influenza is critical to establish immunization recommendations. Influenza or “flu” is caused by influenza viruses A and B and its symptoms range from mild to severe. This virus is constantly evolving; thus, careful monitoring of influenza is important to update immunization and vaccine recommendations yearly. This study used data from surveillance centres in Panama from 2011 to 2017 and evaluated the number of flu cases by age, gender, region, virus type, symptoms, comorbidities, treatment, coinfections with other viruses, and the circulating influenza subtype and the vaccine recommended each year. We found several points: almost 80% of cases were influenza A; most of the positive samples were found in children less than 2 years old and the Panama city region; more than 50% of influenza cases needed hospitalization; and in 2017 a mismatch was detected between the circulating influenza subtype and the recommended vaccine. This study helped to better characterize influenza circulation patterns and the burden of the disease during 2011–2017. We concluded that continuous monitoring of the influenza cases is necessary to establish future vaccination recommendations.

中文翻译：

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2011 年至 2017 年巴拿马季节性甲型和乙型流感的负担：一项观察性回顾性数据库研究。

引言 A 型和 B 型流感病毒不断进化并引起季节性流行病和零星爆发。因此，流行病学监测对于监测其传播模式至关重要。巴拿马提供三价和四价疫苗制剂（分别截至 2016 年和自 2016 年以来）。在此，我们分析了巴拿马的甲型和乙型流感流行病学模式。方法 这是对 2011 年至 2017 年间记录在 Gorgas Memorial Institute for Health Studies 全国监测数据库中的所有实验室确诊流感鼻咽样本的回顾性描述性分析。分析涉及与人口统计信息、病毒类型、亚型和谱系、地理区域、治疗和结果相关的数据。对每个 5 月至 10 月的流感季节，评估了循环和疫苗推荐的 B 谱系之间不匹配的百分比水平。结果 1839例流感病例中，甲型占79.6%，乙型占20.4%。大部分集中在巴拿马城（54.7%），其次是西部（23.2%）和中部（16.7%）地区；在所有地区，甲型和乙型流感病例以 4:1 的比例分布。总体而言，约有一半住院（A 型为 52.0%；B 型为 45.5%），11 人（0.6%）死亡。在 15.1% 的病例中进行了治疗，通常是抗生素治疗。2岁以下的儿童受这种疾病的影响最大。甲型流感每年都在流行，而乙型流感只在2012年、2014年和2017年流行。在2012年5-10月的乙型流感季节，主要谱系是 B/Victoria，2014 年观察到 B/Yamagata 的转变。两个谱系在 2017 年共同流通，导致 38.9% 的 B 谱系水平疫苗不匹配。结论 A 型流感在所有年龄和 2 岁以下儿童中占主导地位，巴拿马城居民报告的传播率最高。2017 年，两种 B 谱系的共同循环导致疫苗不匹配。持续监测季节性流感对于制定免疫建议至关重要。流感或“流感”是由流感病毒 A 和 B 引起的，其症状从轻微到严重不等。这种病毒在不断进化；因此，仔细监测流感对于每年更新免疫接种和疫苗建议非常重要。本研究使用了巴拿马监测中心 2011 年至 2017 年的数据，并按年龄、性别、地区、病毒类型、症状、合并症、治疗、与其他病毒的合并感染以及流行的流感亚型和推荐的疫苗评估了流感病例数每年。我们发现了几点：几乎 80% 的病例是甲型流感；大多数阳性样本发现于 2 岁以下的儿童和巴拿马城地区；超过 50% 的流感病例需要住院治疗；2017 年，在流行的流感亚型和推荐的疫苗之间检测到不匹配。这项研究有助于更好地描述 2011-2017 年流感传播模式和疾病负担。