Transmission of COVID-۱۹ and its Determinants among Close Contacts of COVID-۱۹ Patients

Background: This study aimed to determine the secondary attack rate (SAR) and its determinantsto describe the clinical features and epidemiological aspects of patients and determine the riskfactors of COVID-۱۹ among household contacts in Hamadan Province, west of Iran.Study design: A cohort study.Methods: In this cohort study, a total of ۳۲۳ index cases and ۹۸۹ related close contacts ages morethan ۱۵ years old (family members, relatives, and co-workers) were enrolled using a manual contacttracing approach, and all participants were tested by reverse transcription polymerase chainreaction test. In this research, the frequency of symptoms was assessed, the SAR among contactsof index cases was calculated, and the risk factors of COVID-۱۹ were evaluated by the logisticregression model.Results: The secondary attack rate for total household members of index cases was estimated at۳۱.۷% (۹۵% CI: ۲۸.۸-۳۴.۷). It was found that among household contacts, the highest SARs wererelated to spouses ۴۷.۱% (۹۵% CI: ۳۸.۷-۵۵.۷) and grandparents/parents ۳۹.۳% (۹۵% CI: ۲۹.۴,۴۹.۹) of index cases, who had also higher risks to become secondary cases (adjusted odds ratio[OR]=۲.۹۸, ۹۵% CI: ۱.۳۱-۶.۷۵ and adjusted OR=۲.۷۶, ۹۵% CI: ۱.۱۸-۶.۴۴, respectively).Considering the occupation of contacts, unemployed and retired people and housewives were mostsusceptible for transmission of COVID-۱۹. It was revealed that cough was the most prevalentsymptom among index and secondary cases.Conclusions: Our findings indicated that spouses and grandparents/parents of index cases werethe most susceptible individuals for COVID-۱۹ transmission. Prolonged exposure with index casebefore COVID-۱۹ diagnosis raised the chance of infection among secondary cases.

Keywords:

SARS-CoV-۲ , COVID-۱۹ , Contact tracing , Secondary attack rate , Close contacts