The outbreak of the novel coronavirus disease quickly spread all over China and to more than 20 other countries. Although the virus (SARS-Cov-2) nucleic acid RT-PCR test has become the standard method for diagnosis of SARS-CoV-2 infection, these real-time PCR test kits have many limitations. In addition, high false negative rates were reported. There is an urgent need for an accurate and rapid test method to quickly identify large number of infected patients and asymptomatic carriers to prevent virus transmission and assure timely treatment of patients.We have developed a rapid and simple point-of-care lateral flow immunoassay which can detect IgM and IgG antibodies simultaneously against SARS-CoV-2 virus in human blood within 15 minutes which can detect patients at different infection stages. With this test kit, we carried out clinical studies to validate its clinical efficacy uses. The clinical detection sensitivity and specificity of this test were measured using blood samples collected from 397 PCR confirmed COVID-19 patients and 128 negative patients at 8 different clinical sites. The overall testing sensitivity was 88.66% and specificity was 90.63%. In addition, we evaluated clinical diagnosis results obtained from different types of venous and fingerstick blood samples. The results indicated great detection consistency among samples from fingerstick blood, serum and plasma of venous blood. The IgM-IgG combined assay has better utility and sensitivity compared with a single IgM or IgG test. It can be used for the rapid screening of SARS-CoV-2 carriers, symptomatic or asymptomatic, in hospitals, clinics, and test laboratories.

Highlights d 1.6 million tests identified 1,388 SARS-CoV-2 infections in Guangdong by 19 March d Virus genomes can be recovered using a variety of sequencing approaches d Analyses reveal multiple viral importations with limited local transmission d Effective control measures helped reduce and eliminate chains of viral transmission

The Cre-loxP recombination system is the most widely used technology for in vivo tracing of stem or progenitor cell lineages. The precision of this genetic system largely depends on the specificity of Cre recombinase expression in targeted stem or progenitor cells. However, Cre expression in nontargeted cell types can complicate the interpretation of lineage-tracing studies and has caused controversy in many previous studies. Here we describe a new genetic lineage tracing system that incorporates the Dre-rox recombination system to enhance the precision of conventional Cre-loxP-mediated lineage tracing. The Dre-rox system permits rigorous control of Cre-loxP recombination in lineage tracing, effectively circumventing potential uncertainty of the cell-type specificity of Cre expression. Using this new system we investigated two topics of recent debates-the contribution of c-Kit cardiac stem cells to cardiomyocytes in the heart and the contribution of Sox9 hepatic progenitor cells to hepatocytes in the liver. By overcoming the technical hurdle of nonspecific Cre-loxP-mediated recombination, this new technology provides more precise analysis of cell lineage and fate decisions and facilitates the in vivo study of stem and progenitor cell plasticity in disease and regeneration.

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Organ homeostasis is orchestrated by time- and spatially restricted cell proliferation. Studies identifying cells with superior proliferative capacities often rely on the lineage tracing of a subset of cell populations, which introduces a potential selective bias. In this work, we developed a genetic system [proliferation tracer (ProTracer)] by incorporating dual recombinases to seamlessly record the proliferation events of entire cell populations over time in multiple organs. In the mouse liver, ProTracer revealed more hepatocyte proliferation in distinct zones during liver homeostasis, injury repair, and regrowth. Clonal analysis showed that most of the hepatocytes labeled by ProTracer had undergone cell division. By genetically recording proliferation events of entire cell populations, ProTracer enables the unbiased detection of specific cellular compartments with enhanced regenerative capacities.