3.1 Detection rate of PB and its distribution in different seasons.
Among 4958 children of pneumonia with FOB and BAL therapy, 269 subjects were diagnosed as PB from 2016 to 2019. The annual cases of PB was 30, 42, 67 and 130, respectively, while the annual cases of pneumonia with FOB and BAL for adjuvant therapy was 818, 858, 1471 and 1811. The detection rate of PB in pneumonia was 3.7%, 4.9%, 4.6% and 7.2%, respectively ( 2016 to 2019) ( figure 1). The seasonal distribution of PB from 2016 to 2019 was shown in figure 2 and the peak incidence was observed in 2019 winter.