Abstract:Objective To analyze the epidemiological characteristics of Chlamydia psittaci pneumonia diagnosed by macrogenomic next-generation sequencing (mNGS). Methods The mNGS data of metagenome were provided by Vision Medicals Center for Medical Research (dataset Ⅰ, November 2019 to January 2021) and Dinfectome Inc. (dataset Ⅱ, April 2019 to December 2020), and including: sex, age, city, test sample type, test time, the number of DNA sequence of Chlamydia psittaci positive patients and the number of pneumonia patients detected by mNGS in the corresponding time period. The data were analyzed by statistical software. Results A total of 11 514 samples were examined and 132 patients were positive, with a detection rate of 1.1% (132/11 514). There were 44 cases in spring and summer, accounting for 33.3% of the total number of cases. There were 88 cases in autumn and winter, accounting for 66.7% of the total number of cases. The positive rate of Chlamydia psittaci infection was 0.5% (9/1 756) of patients in northern China and was 1.3% (123/9 758)of patients in southern China. All 132 positive cases were mainly treated by respiratory department, critical medicine department, emergency department and infection department, accounting for 94.7% of the total cases (125/132). The number of samples from positive cases was 179, of which 172 were alveolar lavage fluid, blood and sputum, accounting for 96.1% (172/179). The positive rate of alveolar lavage fluid samples was high, with dataset Ⅰ and dataset Ⅱ being 100% and 96.8% respectively, while the positive rate of blood samples was slightly lower, at 81.3% and 67.6%, respectively. Conclusions The Chlamydia psittaci pneumonia occurs frequently in autumn and winter. The detection rate in the areas south of the Qinling Mountains-Huaihe River is higher than that in the areas north of the Qinling Mountains-Huaihe River. Alveolar lavage fluid is the preferred specimen for chlamydia psittaci detection.