Abstract: Objective To investigate the epidemiological characteristics, source of infection, and transmission route of a cluster associated with the corona virus disease 2019(COVID-19), and to provide evidence for prevention and control strategies. Methods Field epidemiological investigation and analysis were performed on 4 cases(A-D). The survey contents included basic information, onset of cases, diagnosis and treatment, exposure history and close contacts. Results Cases A, B, and C all had symptoms such as fever, fatigue, and muscle soreness. Case D was an asymptomatic case. Computed tomography showed interstitial hyperplasia with infection in all of the patients lungs. The interval from onset to treatment was 0-3 days, and the interval from onset to hospitalization was 1-7 days. Case B was the close contact of case A, and case D was the close contact of case C, respectively. Cases A, C, and D were colleagues, and they all went to Beijing, Taian and other places to participate in the companys party activities before the onset. Cases A and B were father-daughter relationship. Conclusion The outbreak was an infection caused by company gatherings and families infection. Cases A, C, and D may have been infected during a meeting in Beijing, and case B was an infection caused by exposure to case A. Investigation, isolation and testing of close contacts should be strengthened to reduce the concentration of personnel and close attention should be paid to asymptomatic cases.

Key words: Corona virus disease 2019, Epidemiology, Field investigation