Objective: To understand the epidemiological characteristics of COVID-19 cases in different epidemic stages in Gansu province. Methods: Epidemiological investigation was conducted to collect the information of confirmed COVID-19 cases, including demographic, epidemiological and clinical information. Results: As of 25 February 2020, a total of 91 confirmed COVID-19 cases had been reported in Gansu. The epidemic of COVID-19 in Gansu can be divided as three different stages, i.e. imported case stage, imported-case plus indigenous case stage, and indigenous case stage. A total of 63 cases were clustered cases (69.23%), 3 cases were medical staff infected with non-occupational exposure. The initial symptoms included fever (54.95%, 50/91), cough (52.75%, 48/91), or fatigue (28.57%, 26/91), the proportion of each symptom showed a decreasing trend along with the three epidemic stages, but only the differences in proportions of fever (trend χ2=2.20, P<0.05) and fatigue (trend χ2=3.18, P<0.05) among the three epidemic stages were statistically significant. The cases with critical severe symptoms accounted for 42.85% (6/14), 23.73% (14/59) and 16.67% (3/18), respectively, in three epidemic stages, showed a decreasing trend (H=6.45, P<0.05). Also, the incubation period prolonged along with the epidemic stage (F=51.65, P<0.01), but the intervals between disease onset and hospital visit (F=5.32, P<0.01), disease onset and diagnosis (F=5.25, P<0.01) became shorter along with the epidemic stage. Additionally, the basic reproduction number (R0) had decreased from 2.61 in imported case stage to 0.66 in indigenous case stage. Conclusions: The COVID-19 epidemic in Gansu was caused by the imported cases, and about 2/3 cases were clustered ones. No medical worker was observed to be infected by occupational exposure. With the progression of COVID-19 epidemic in Gansu, the change in initial symptom and incubation period suggests, the early screening cannot only depend on body temperature monitoring.
目的： 对甘肃省确诊的新型冠状病毒肺炎（COVID-19）病例进行流行病学特征分析，探索疫情流行的阶段性特征和变化。 方法： 通过流行病学调查收集甘肃省COVID-19病例资料，包括基本资料、流行病学史、发病、就诊和确诊时间、临床表现等信息。 结果： 截至2020年2月25日，甘肃省共报告91例确诊病例，COVID-19流行分为输入病例期、输入病例与本地病例并存期、本地病例为主期3个阶段。聚集性疫情病例共63例（69.23%）。医务人员有3例，均为非职业暴露感染。首发症状为发热、咳嗽和乏力的比例分别为54.95%（50/91）、52.75%（48/91）和28.57%（26/91），且在3个阶段中的比例呈下降趋势，但只有发热与乏力症状的差异有统计学意义（趋势χ2值分别为2.20和3.18，P<0.05）；3个阶段的重型/危重型病例比例分别为42.86%（6/14）、23.73%（14/59）和16.67%（3/18），呈下降趋势（H＝6.40，P<0.05）；潜伏期随着疫情的3个阶段有延长的趋势（F＝51.65，P<0.01）；发病到就诊、发病到确诊的时间间隔随着疫情进展有缩短的趋势（F值分别为5.32和5.25，P<0.01）；基本再生数（R0）从输入病例期的2.61降至本地病例为主期的0.66。 结论： 甘肃省COVID-19流行早期均为湖北省输入，聚集性疫情占三分之二，未发现医务人员职业性暴露感染。总体流行呈阶段性变化特征，随着疫情进展有首发症状不明显和潜伏期延长的特点，并提示体温监测不能作为单一的早期筛查手段。.
Keywords: COVID-19; Epidemiological characteristic.