COVID-19 Outbreak Caused by Contaminated Packaging of Imported Cold-Chain Products — Liaoning Province, China, July 2020

Abstract

What is known about this topic? Few major outbreaks of coronavirus disease 2019 have occurred in China after major nonpharmaceutical interventions and vaccines have been deployed and implemented. However, sporadic outbreaks that had high possibility to be linked to cold chain products were reported in several cities of China.. What is added by this report?In July 2020, a COVID-19 outbreak occurred in Dalian, China. The investigations of this outbreak strongly suggested that the infection source was from COVID-19 virus-contaminated packaging of frozen seafood during inbound unloading personnel contact. What are the implications for public health practice? Virus contaminated paper surfaces could maintain infectivity for at least 17-24 days at -25 ℃. Exposure to COVID-19 virus-contaminated surfaces is a potential route for introducing the virus to a susceptible population. Countries with no domestic transmission of COVID-19 should consider introducing prevention strategies for both inbound travellers and imported goods. Several measures to prevent the introduction of the virus via cold-chain goods can be implemented. INVESTIGATION AND RESULTSCOVID-19 cases were diagnosed by a local hospital in Dalian according to the Protocol for Prevention and Control of COVID-19 (Edition 6) issued by China CDC (1). In this study, a confirmed case was defined as having a throat swab that tested positive for COVID-19 virus RNA by RT-qPCR; an undiscovered infected case was defined as having a sera sample that tested positive for COVID-19 antibodies but negative for COVID-19 virus RNA. Detailed epidemiological investigation for early cases were conducted through in-person interviews for their travel history, activity, work history, and contact history starting 14 days (incubation period) before the onset of illness. Environmental samples and cold-chain product samples collected from Company K were further tested with RT-qPCR. Individuals who had contact with the China CDC Weekly Chinese Center for Disease Control and Prevention CCDC Weekly / Vol. 3 / No.

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“…This study also finds other potential transmission between two probable cases regardless of P1 and P2’s connection in C1’s contact network ( Figure 1 ). A previous study in Liaoning Province also showed a phenomenon in an outbreak that made it difficult to determine the first index case, persons who were double-positive for IgM and IgG but negative for nucleic acid testing were also found, which supported our finding ( 10 ).…”

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