Objective  To analyze infection risk and its influencing factors among close contacts of patients with novel coronavirus disease 2019 (COVID-19) in Liaoning province for providing evidences to develop precise prevention and control strategies.

  Methods  We collected the information on all close contacts of COVID-19 cases reported in Liaoning province from January 22 to February 29, 2020. Unconditional logistic regression analysis was adopted to explore disparities in the infection risk among different close contacts.

  Results  Of the 2 784 close contacts identified, 67 (2.41%) infections were confirmed by virus nucleic acid test. Univariate analysis results demonstrated that compared with those aged 16 – 45 years, the close contacts of other age groups were more likely to be infected; the close contacts being an index case′ relative or cohabitating with an index case had a higher infection risk. After excluding 25 close contacts with a history of traveling in other provinces, the results of multivariate analysis revealed that in comparison with those having no family relationship with the index case, the close contacts being the index cases′ distant relatives (odds ratio OR = 4.845, 95% confidence interval 95% CI: 1.350 – 17.393), immediate relatives (OR = 27.571, 95% CI: 6.361 – 119.501), and spouses (OR = 26.200, 95% CI: 4.702 – 146.000) were at a significantly increased infection risk. The disease severity of the infected close contacts was positively correlated with age (r = 0.445, P < 0.001) and disease severity of the index case (r = 0.243, P = 0.048).

  Conclusion  The infection risk of close contacts of patients with COVID-19 is related to age, the relationship and the mode of contact with the index case. The disease severity of an infected close contact is related to the contact′s age and the disease severity of the index case. Close contact is a main route for COVID-19 transmission and family clustering is prevalent in COVID-19 epidemic.