Abstract
Standard contact tracing practice for COVID-19 is to identify persons exposed to an infected person during the contagious period, assumed to start two days before symptom onset or diagnosis. In the first large cohort study on backward contact tracing for COVID-19, we extended the contact tracing window by 5 days, aiming to identify the source of the infection and persons infected by the same source. The risk of infection amongst these additional contacts was similar to contacts exposed during the standard tracing window and significantly higher than symptomatic individuals in a control group, leading to 42% more cases identified as direct contacts of an index case. Compared to standard practice, backward traced contacts required fewer tests and shorter quarantine. However, they were identified later in their infectious cycle if infected. Our results support implementing backward contact tracing when rigorous suppression of viral transmission is warranted.
【초록키워드】 COVID-19, quarantine, Infection, Diagnosis, Contact tracing, Viral transmission, large cohort, risk of infection, Contact, index case, Standard, Support, symptom onset, control group, contagious period, identify, required, significantly higher, assumed, symptomatic individual, 【제목키워드】 COVID-19, Contact tracing, Efficiency, empirical evidence,