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Porcine deltacoronavirus (PDCoV) is an emerging swine coronavirus that causes severe diarrhea to pigs of all ages, especially the suckling piglets under one-week-old. We previously isolated a highly pathogenic PDCoV strain, CZ2020, from a diarrheal piglet and have passaged it for over 100 passages. The adaptability of the CZ2020 increased gradually in vitro as the passage increased. Amino acid mutations were observed in pp1a, pp1ab, spike, envelop, and membrane proteins, and the spike protein accounts for 66.7% of all amino acid mutations. Then, the high passage strains, CZ2020-F80 and CZ2020-F100, were selected for evaluation of the pathogenicity in three-day-old piglets to examine whether these amino acid changes affected their virulence. At 2 days postchallenge (DPC), 2/5 piglets started to show typical diarrhea, and at 4 DPC, severe diarrhea was observed in the CZ2020-challenged piglets. Viral RNA could be detected at 1 DPC in rectal swabs and reached its highest at 4 DPC in the CZ2020-challenged group. CZ2020-F80- and CZ2020-F100-challenged groups have one piglet exhibiting mild diarrhea at 4 and 6 DPC, respectively. Compared with the CZ2020-challenged group, the piglets in CZ2020-F80- and F100-challenged groups had lower viral loads in rectal swabs, intestines, and other organs. No obvious histopathological lesions were observed in the intestines of CZ2020-F80- and F100-challenged piglets. Virulent PDCoV infection could also induce strong interferons and proinflammatory cytokines in vitro and in vivo. These data indicate that the strains, CZ2020-F80 and CZ2020-F100, were significantly attenuated via serial passaging in vitro and have the potential for developing attenuated vaccine candidates. [ABSTRACT FROM AUTHOR]

The novel coronavirus disease (COVID‐19) poses a serious threat to global public health and economics. Serial interval (SI), time between the onset of symptoms of a primary case and a secondary case, is a key epidemiological parameter. We estimated SI of COVID‐19 in Shenzhen, China based on 27 records of transmission chains. We adopted three parametric models: Weibull, lognormal and gamma distributions, and an interval‐censored likelihood framework. The three models were compared using the corrected Akaike information criterion (AICc). We also fitted the epidemic curve of COVID‐19 to the logistic growth model to estimate the reproduction number. Using a Weibull distribution, we estimated the mean SI to be 5.9 days (95% CI: 3.9–9.6) with a standard deviation (SD) of 4.8 days (95% CI: 3.1–10.1). Using a logistic growth model, we estimated the basic reproduction number in Shenzhen to be 2.6 (95% CI: 2.4–2.8). The SI of COVID‐19 is relatively shorter than that of SARS and MERS, the other two betacoronavirus diseases, which suggests the iteration of the transmission may be rapid. Thus, it is crucial to isolate close contacts promptly to effectively control the spread of COVID‐19. [ABSTRACT FROM AUTHOR]

Summary: Porcine deltacoronavirus (PDCoV) has emerged and spread throughout the porcine industry in many countries over the last 6 years. PDCoV caused watery diarrhoea, vomiting and dehydration in newborn piglets. A sensitive diagnostic method would be beneficial to the prevention and control of PDCoV infection. Recombinase polymerase amplification (RPA) is an isothermal amplification method which has been widely used for virus detection. A probe‐based reverse transcription RPA (RT‐RPA) assay was developed for real‐time detection of PDCoV. The amplification can be finished in 20 min and fluorescence monitoring was performed by a portable device. The lowest detection limit of the PDCoV RT‐RPA assay was 100 copies of RNA molecules per reaction; moreover, the RT‐RPA assay had no cross‐reaction with other common swine viruses. The clinical performance of the RT‐RPA assay was evaluated using 108 clinical samples (54 intestine specimens and 54 faecal swab specimens). The coincidence rate of the detection results for clinical samples between RT‐RPA and RT‐qPCR was 97.2%. In summary, the real‐time RT‐RPA assay offers a promising alternative to RT‐qPCR for point‐of‐care detection of PDCoV. [ABSTRACT FROM AUTHOR]

Elizabethkingia miricola is a Gram‐negative rod which has been incriminated in severe infections in humans. Recently, a serious infectious disease was identified in Chinese spiny frogs (Quasipaa spinosa), in the Sichuan Province of China; the disease was characterized by corneal opacity, the presence of ascites and neurological symptoms. A Gram‐negative bacillus was isolated from the liver, spleen and kidney of the diseased frogs. Experimental infection test revealed that the bacillus could infect the frogs Q. spinosa and the LD50 value was 1.19 × 106 cfu per frog. The isolated Gram‐negative bacillus was identified as E. miricola according to phenotypic characteristics, 16S rRNA and gyrB gene sequence analysis. The isolated strain was only susceptible to florfenicol among all investigated chemotherapeutic agents. Histological examination revealed that E. miricola infection caused pathological lesions to multiple organs and tissues, especially in the liver, brain, kidney. These results confirmed that E. miricola is an emerging pathogen of Chinese spiny frogs. [ABSTRACT FROM AUTHOR]