Abstract：
Legionnaires\' disease (LD) (Legionella) is a common cause of community-acquired pneumonia (CAP) in those requiring hospitalization. Geographical variation in the importance of Legionella species as an aetiologic agent of CAP is poorly understood. We performed a systematic review and meta-analysis of population-based observational studies that reported the proportion of Legionella infection in patients with CAP (1 January 1990 to 31 May 2020). Using five electronic databases, articles were identified, appraised and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The quality of the included studies was assessed using the Newcastle-Ottawa Scale. Univariate and multivariate meta-regression analyses were conducted using study design, WHO region, study quality and healthcare setting as the explanatory variables. We reviewed 2778 studies, of which 219 were included in the meta-analysis. The mean incidence of CAP was 46.7/100,000 population (95% CI: 46.6-46.8). The mean proportion of Legionella as the causative agent for CAP was 4.6% (95% CI: 4.4 to 4.7). Consequently, the mean Legionella incidence rate was 2.8/100,000 population (95% CI: 2.7-2.9). There was significant heterogeneity across all studies I2 = 99.27% (p < 0.0001). After outliers were removed, there was a decrease in the heterogeneity (I2 = 43.53%). Legionella contribution to CAP has a global distribution. Although the rates appear highest in high income countries in temperate regions, there are insufficient studies from low- and middle-income countries to draw conclusions about the rates in these regions. Nevertheless, this study provides an estimate of the mean incidence of Legionella infection in CAP, which could be used to estimate the regional and global burden of LD to support efforts to reduce the impact of this infection as well as to fill important knowledge gaps.
摘要：
军团病（LD）（军团菌）是需要住院治疗的社区获得性肺炎（CAP）的常见原因。军团菌物种作为CAP病因的重要性的地理差异知之甚少。我们对基于人群的观察性研究进行了系统评价和荟萃分析，这些研究报告了军团菌感染在CAP患者中的比例（1990年1月1日至2020年5月31日）。使用五个电子数据库，文章被识别，根据系统审查和荟萃分析（PRISMA）指南的首选报告项目进行评估和报告。使用纽卡斯尔-渥太华量表评估纳入研究的质量。使用研究设计进行单变量和多变量荟萃回归分析，世卫组织区域，研究质量和医疗保健环境作为解释变量。我们回顾了2778项研究，其中219人纳入荟萃分析。CAP的平均发生率为46.7/100,000人群（95％CI：46.6-46.8）。军团菌作为CAP病原体的平均比例为4.6％（95％CI：4.4至4.7）。因此,军团菌平均发病率为2.8/100,000(95%CI:2.7-2.9).在所有研究中存在显著的异质性I2=99.27%(p<0.0001)。删除异常值后，异质性降低(I2=43.53%)。军团菌对CAP的贡献在全球范围内分布。尽管温带地区的高收入国家的比率似乎最高，低收入和中等收入国家的研究不足，无法对这些地区的比率得出结论。然而，这项研究提供了CAP中军团菌感染的平均发生率的估计，这可用于估计LD的区域和全球负担，以支持减少这种感染的影响以及填补重要的知识空白的努力。
