Risk factors associated with COVID-19 infection: a retrospective cohort study based on contacts tracing.

ABSTRACT

This study aimed to estimate the attack rates, and identify the risk factors of COVID-19 infection. Based on a retrospective cohort study, we investigated 11,580 contacts of COVID-19 cases in Guangdong Province from 10 January to 15 March 2020. All contacts were tested by RT-PCR to detect their infection of SARS-COV-2. Attack rates by characteristics were calculated. Logistic regression was used to estimate the risk factors of infection for COVID-19. A total of 515 of 11,580 contacts were identified to be infected with SARS-COV-2. Compared to young adults aged 20-29 years, the infected risk was higher in children (RR 2.59, 95%CI 1.79-3.76), and old people aged 60-69 years (RR 5.29, 95%CI 3.76-7.46). Females also had higher infected risk (RR 1.66, 95%CI 1.39-2.00). People having close relationship with index cases encountered higher infected risk (RR for spouse 20.68, 95%CI 14.28-29.95; RR for non-spouse family members 9.55, 95%CI 6.73-13.55; RR for close relatives 5.90, 95%CI 4.06-8.59). Moreover, contacts exposed to index case in symptomatic period (RR 2.15, 95%CI 1.67-2.79), with critically severe symptoms (RR 1.61, 95%CI 1.00-2.57), with symptoms of dizzy (RR 1.58, 95%CI 1.08-2.30), myalgia (RR 1.49, 95%CI 1.15-1.94), and chill (RR 1.42, 95%CI 1.05-1.92) had higher infected risks. Children, old people, females, and family members are susceptible of COVID-19 infection, while index cases in the incubation period had lower contagiousness. Our findings will be helpful for developing targeted prevention and control strategies to combat the worldwide pandemic.