Abstract
What is already known on this topic? Contact tracing and testing with isolated medical care of identified cases is a key strategy for interrupting chains of transmission of COVID-19 and reducing mortality associated with COVID-19. At the early phases of the COVID-19 pandemic, due to test capacity limitations, case finding often started from suspected cases. What is added by this report? The index patient infected 74 individuals who were close contacts that were identified through contact tracing, and exposed individuals were monitored in quarantine with daily polymerase chain reaction (PCR) testing. All individuals were asymptomatic initially, but all PCR-positive individuals eventually developed symptoms. Infectivity was documented up to 8 days before being confirmed as a symptomatic case, approximately 4 days before turning PCR positive. What are the implications for public health practice? During an outbreak, we suggest tracing close contacts from both PCR-positive individuals and suspected cases, rather than from suspected cases alone. Due to the long period of infectivity before turning PCR positive or developing symptoms, close contacts that had contact with a newly PCR positive case within 4 days should be judged as at risk of being infected; close contacts that had contact within 8 days of a newly symptomatic case should be judged as at risk being infected.
Highlights
Contact tracing — along with robust testing, isolation, and care of cases — is a key strategy for interrupting chains of transmission of coronavirus disease 2019 (COVID-19), caused by COVID-19 virus known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and reducing mortality associated with COVID-19 [1,2]
In response to the outbreak, close contacts were quarantined, and nucleic acid testing was conducted daily to determine whether the contacts had been infected
As soon as polymerase chain reaction (PCR)-positive individuals developed symptoms, they would be classified by physicians as confirmed cases, and their National Infectious Diseases Reporting System (NIDRS) record would be updated with their new status as a confirmed COVID-19 case
Summary
Index and First-Generation Cases in a COVID-19 Outbreak — Jilin Province, China, 2021. On January 9, 2021, the first case (Patient A) of a COVID-19 outbreak arrived unknowingly infected in Dongchang District, Tonghua City, Jilin Province, China. Once Patient A had been diagnosed using polymerase chain reaction (PCR) testing as being infected, lecture participants were located and placed in quarantine where they were tested with PCR and evaluated for COVID-19 symptoms every day. This careful observation period under quarantine provided an opportunity to assess infectivity period, incubation time, the time between becoming PCR positive and developing symptoms. We report results of our study of first-generation cases to further improve investigation and management of close contacts of COVID-19 cases
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