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ABSTRACT Introduction: Severe fever with thrombocytopenia syndrome virus (SFTSV) is a newly emerged virus that poses a great threat to human health because of high fatality rate. Methods: To develop sensitive and specific sero-diagnostic systems for SFTSV infections, monoclonal antibodies (MAbs) against recombinant SFTSV nucleocapsid (rSFTSV-N) protein were developed by immunizing BALB/C mice with rSFTSV-N protein and fusing the spleen cells with SP2/0 myeloma cells. Three hybridoma cell lines secreting MAbs against rSFTSV-N were obtained. MAb based IgG sandwich enzyme linked immunosorbent assay (ELISA) and IgM capture ELISA systems were established by using the newly developed MAbs. One hundred fifteen clinical suspected SFTS patients serum samples were used to evaluate the newly established systems by comparing with the total antibody detecting sandwich ELISA system and indirect ELISA systems. Results: The MAbs based sandwich IgG ELISA was perfectly matched with that of the total antibody sandwich ELISA and the indirect IgG ELISA. IgM capture ELISA results perfectly matched with that of the total antibody sandwich ELISA while detecting eight additional positive samples missed by the indirect IgM ELISA. Conclusions: The MAbs against rSFTSV-N protein offer new tools for SFTSV studies and our newly developed MAb-based IgG and IgM capture ELISA systems would offer safe and useful tools for diagnosis of SFTS virus infections and epidemiological investigations.
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Objective@#To learn the epidemiological characteristics of family clusters of COVID-19 in Henan Province from January 23 to February 22, 2020, so as to provide reference for the prevention and control. @*Methods@#The data of family clusters of COVID-19 in Henan Province from January 23 to February 22 was retrieved from Public Health Emergency Management System, the epidemiological characteristics of time, space, population distribution and clinical feasures were analyzed. @*Results@#By February 22, there were 202 family clusters of COVID-19, with 546 cases reported in Henan Province, including 493 ( 90.29% ) confirmed cases and 53 ( 9.71% ) asymptomatic cases. There were 247 ( 45.24% ) imported cases and 299 ( 54.76% ) local cases. Most of the clusters were reported from January 25 to February 7, with 129 clusters accounting for 63.86% . The cases reported before February 5 were mainly imported ( 153 cases, 57.09% ) , after that local cases were predominant ( 168 cases, 68.29% ) . Eighteen cities in Henan Province all reported family clusters of COVID-19, with Xinyang, Zhengzhou, Nanyang, Zhumadian and Shangqiu as the top five. Most of the confirmed cases ( 430, 87.22% ) were mild. The median and longest incubation period was 8 and 17 days, respectively. The intergenerational distribution was dominated by first-generation and second-generation cases ( 537 cases, 98.35% ) . A total of 5 635 close contacts were tracked down, of whom 262 were secondary cases, with an incidence rate of 4.65%. The first cases of the family clusters were mainly imported from other provinces ( 149 cases, 73.76% ) .@*Conclusions @#The family clusters of COVID-19 in Henan Province were concentrated from January 25 to February 7. The source of infection mainly comes from other provinces. Most of the cases are first-and second-generation cases, with longer incubation period. Close contacts have higher incidence rate.