Analysis on the surveillance of infectious disease related public health bud-events in Shanghai from 2017 to 2020

Objective To determine the epidemiological characteristics of infectious disease related public health bud-events in Shanghai and assess the effects of bud-event surveillance， so as to provide scientific evidence for improving the surveillance system.

Methods Surveillance data of infectious disease related public health bud-events were collected from 16 districts of Shanghai from 2017 through 2020. Then the data were analyzed and compared with infectious disease related public health emergencies during the same period.

Results A total of 6 376 infectious disease related public health bud-events were documented in Shanghai in 2017‒2020， which involved 29 792 cases. There were two seasonal peaks， April through June and November through December. Clustered events accounted for 38.85%， mainly caused by chickenpox （14.10%）， hand，foot and mouth disease （11.17%） and norovirus-associated infectious diarrhea （6.54%）. The 36.73% of the bud-events occurred in school settings， which involved 24 718 cases （accounting for 83.00% of all cases）. Median time duration between onset date of the first cases and report date of the events was 4 days， and median duration of the events was 14 days， demonstrating positive correlation. In addition， all the infectious disease related public health emergencies（n=77） from 2017 through 2020 were classified as common events or unclassified. The proportion of infectious disease related public health emergencies in the bud-events during the same period was 1.21%， and that of infectious disease related public health emergencies in the bud-events in school settings was 2.48%.

Conclusion Two peaks of infectious disease related public health bud-events are observed in spring as well as autumn and winter in Shanghai from 2017 through 2020. Schools should be prioritized for control and prevention of infectious diseases. Bud-event surveillance system has been contributable to the prevention and control of public health emergencies， especially in the early detection， reporting and control of clustered events in schools. Bud-event surveillance system should be further improved and assessed comprehensively.