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Duck is commonly used for premium meat adulteration. A simple, rapid, accurate, and affordable method is urgently needed for duck ingredient identification. Therefore, we developed two recombinase polymerase amplification (RPA) assays based on the duck-specific Cytb gene for rapid detection of duck ingredient in this study, and there were less than 30 min from sample to answer. Two RPA assays were validated to demonstrate good inter- and intra-species specificity. The real-time RPA could detect as low as 10 pg of duck DNA while the RPA combined with lateral flow test strips (LFS RPA) could detect down to 1 pg, and both could detect 0.1% duck meat adulteration. Then the two RPA assays applicability was confirmed using 113 different foods. The effects of background DNA and whole blood on RPA amplification were also analyzed, which did not affect the feasibility of the developed two RPA assays. The developed real-time RPA and LFS RPA would be promising user-friendly on-site detection methods for rapid detecting duck ingredient in different meat products.

BackgroundSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a new type of virus that firstly confirmed in Wuhan, China recently. SARS-CoV-2 mainly spread through droplets. Infection characteristics data of SARS-CoV-2 is still limited, especially about asymptomatic infection, familial aggregation infection and infection risk in family member.MethodsFrom 2nd January 2020 to 23th February 2020, we have screened 22,729 throat swab samples from individuals with either have contact history of imported personnel, out-of-city travel or residence history or flu-like symptoms during the past 14 days. SARS-CoV-2 RNA was extracted and detected by real-time PCR. Data were analyzed using SPSS version 19 (IBM, Armonk, NY, USA). The results were confirmed by the Pearson χ2 test; P ＜ 0.05 was considered statistically significant.Results35 SARS-CoV-2 positive patients were found, 22 were asymptomatic infection, and 31 were familial aggregation infection. Odds ratio of SARS-CoV-2 infection risk between family aggregated close contacts and overall close contacts was 29.40 (95％ confidence interval: 13.99 - 62.205, χ2 = 140.23, P ＜ 0.001); odds ratio of SARS-CoV-2 infection risk between family aggregated close contacts and non-family aggregated close contacts was 703.50 （95％ confidence interval: 89.53 - 5527.95, χ2 = 282.659, P ＜ 0.001). One SARS-CoV-2 positive patient infected 2.08 (25/12) people on average under social control without separate isolation.ConclusionsSocial control is effective in SARS-CoV-2 inhibition, but self-isolation and screening should be added as supplementary means to avoid familial aggregation infection and find out asymptomatic patients.