Objective Based on the investigation of an outbreak of cluster COVID-19 epidemic in a district of Chongqing

the disease transmission chain and mode were analyzed in order to provide a scientific basis for relevant departments to formulate prevention and control strategies and guide the public to protect themselves personally.Methods The confirmed cases and their close contacts and general contacts were investigated by on-the-spot epidemiological methods

and the nasopharyngeal swab samples were detected for coronavirus nucleic acid testing by real-time fluorescence PT-PCR.Results The source of infection of this cluster epidemic was case A

which had a history of living in Wuhan

Hubei Province.Case B was a second-generation case.CT showed right lung infection.Blood routine test showed that the number of white blood cells and lymphocytes were 5.30×10

9

/L and 3.93×10

9

/L

respectively.Case C

a third-generation case

is a cohabiting boyfriend of case B.CT showed bilateral lung infection.Blood routine test showed that the number of white blood cells and lymphocytes were 4.02×10

9

/L and 1.49×10

9

/L

respectively.Conclusion COVID-19 is easy to spread in the family through contact and droplet transmission.Active and decisive prevention and control measures should be taken to prevent and control the spread of the epidemic.