Imported COVID-19 cases pose new challenges for ChinaDear editor , Recently, a letter in your journal predicted the trend of the spread of the novel coronavirus disease 2019 in China, an illness caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), 1 , 2 would end after March 20, 2020. 3 Currently, the COVID-19 has spread around the globe, with the center of the epidemic shifting from China to Europe and the United States. 4 As of March 24, 2020, a total of 372,757 cases have been confirmed worldwide, with a death toll of 16,231 (WHO, Coronavirus disease 2019 Situation Report 64, March 24, 2020). Italy, in particular, had thus far diagnosed 63,927 patients, 6077 of whom had lost their lives. That translates to a mortality rate of 9.51%, which is more than twice as high as that of China's 4.02% (3283/81,747). The greater share of elderly patients with confirmed COVID-19 infection in Italy along with the population's significantly higher median age may partly explain the differences in cases and case-fatality rates between the two nations. 5 Countries such as the United States (42,164 cases), Spain (33,089 cases), Germany (29,212 cases), and France (19,615 cases) have seen an explosive increase in confirmed cases, with the rate of growth showing no hint of slowing down.For China-the initial epicenter of the outbreak-two stages of the epidemic have passed ( Fig. 1 A). The first stage is the outbreak period (December 31, 2019 to February 29, 2020), which entailed the period from the first detection of cases to the peak of the epidemic which saw a rapid increase in the number of confirmed cases, and to the time when the growth rate slowed down to less than 200 new confirmed cases per day. In the second stage, which lasted from March 1, 2020 to March 21, 2020, the number of existing cases in most Chinese provinces was reduced to less than 10, respectively, whilst the number of newly confirmed cases in Wuhan, Hubei province, the worst-hit city, was slowly approaching zero. It was during this stage-more specifically on the March 4-that foreign imported cases to appear. During these two stages, the Chinese government, its populous, and its medical professionals had managed to stabilized the deadly epidemic with great deliberation and sacrifices. 6 Currently, however, the situation in China has entered its third stage-recontamination through close contact with foreign infection, as demonstrated by the emergence of second-generation case originated from imported cases first reported in Guangzhou, Guangdong province on March 22, 2020 ( Fig. 1 B). As of March 24, 2020, there were 427 imported cases and 3 second-generation cases originated from imported cases, one each in Beijing, Shanghai and Guangzhou (National Health Commission of the People's Republic of China). It shows that China needs to pay more attention to the control of imported cases and reflect on the measures previously taken against imported cases.

Newcastle disease virus (NDV) is distributed worldwide and has caused significant losses to the poultry industry. Almost all virulent NDV strains belong to class II, among which genotype VII is the predominant genotype in China. However, the molecular evolution and phylodynamics of class II genotype VII NDV strains in China remained largely unknown. In this study, we identified 13 virulent NDV including 11 genotype VII strains and 2 genotype IX strains, from clinical samples during 1997 to 2019. Combined NDV sequences submitted to GenBank, we investigate evolution, and transmission dynamics of class II NDVs in China, especially genotype VII strains. Our results revealed that East and South China have the most genotypic diversity of class II NDV, and East China might be the origin of genotype VII NDVs in China. In addition, genotype VII NDVs in China are presumably transmitted by chickens, as the virus was most prevalent in chickens. Furthermore, codon usage analysis revealed that the F genes of genotype VII NDVs have stronger adaptation in chickens, and six amino acids in this gene are found under positive selection via selection model analysis. Collectively, our results revealed the genetic diversity and evolutionary dynamics of genotype VII NDVs in China, providing important insights into the epidemiology of these viruses in China.

Newcastle disease (ND) is an infectious disease that affects both wild and domestic birds worldwide, causing significant losses to the poultry industry (Swayne, 2013). The economic burden of ND in poultry is attributed not only to the mortality and depopulation of stock but also to the preventative measures and restriction of poultry trade during and immediately after outbreaks (Hicks, Dimitrov, Afonso, Ramey, & Bahl, 2019;Leslie, 2000). ND is caused by Newcastle disease virus (NDV), a member of the genus Orthoavulavirus of the family Paramyxoviridae and the subfamily Avulavirinae, whose genome is a single-stranded, negative-sense RNA, coding for six structural proteins, namely nucleoprotein (NP), phosphoprotein (P), matrix protein (M), fusion protein (F), hemagglutinin-neuraminidase (HN) and large protein (L), and two non-structural proteins, V and W (Alexander, 2000).Based on the completed F gene sequence (1662 nt), NDV is phylogenetically divided into two groups with a single serotype,

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Newcastle disease (ND), caused by the Newcastle disease virus (NDV), is a highly virulent infectious disease of poultry. Virulent NDV can cause severe autophagy and inflammation in host cells. While studies have shown a mutual regulatory relationship between autophagy and inflammation, this relationship in NDV infection remains unclear. This study confirmed that NDV infection could trigger autophagy in DF-1 cells to promote cytopathic and viral replication. NDV-induced autophagy was positively correlated with the mRNA levels of inflammatory cytokines such as IL-1β, IL-8, IL-18, CCL-5, and TNF-α, suggesting that NDV-induced autophagy promotes the expression of inflammatory cytokines. Further investigation demonstrated that NLRP3 protein expression, Caspase-1 activity, and p38 phosphorylation level positively correlated with autophagy, suggesting that NDV-induced autophagy could promote the expression of inflammatory cytokines through NLRP3/Caspase-1 inflammasomes and p38/MAPK pathway. In addition, NDV infection also triggered mitochondrial damage and mitophagy in DF-1 cells, but did not result in a large leakage of reactive oxygen species (ROS) and mitochondrial DNA (mtDNA), indicating that mitochondrial damage and mitophagy do not contribute to the inflammation response during NDV infection.

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Infectious bronchitis virus (IBV) is distributed worldwide and causes significant losses in the poultry industry. In recent decades, lineages GI-19 and GI-7 have become the most prevalent IBV strains in China. However, the molecular evolution and phylodynamics of the lineage GI-7 IBV strains remain largely unknown. In this study, we identified 19 IBV strains from clinical samples from January 2021 to June 2022 in China, including 12 strains of GI-19, 3 strains of GI-7, and 1 strain each of GI-1, GI-9, GI-13, and GI-28. These results indicated that lineages GI-19 and GI-7 IBVs are still the most prevalent IBVs in China. Here, we investigated the evolution and transmission dynamics of lineage GI-7 IBVs. Our results revealed that the Taiwan province might be the origin of lineage GI-7 IBVs and that South China plays an important role in the spread of IBV. Furthermore, we found low codon usage bias of the S1 gene in lineage GI-7 IBVs. This allowed IBV to replicate in the host during evolution as a result of reduced competition, mainly driven by natural selection and mutational pressure, where the role of natural selection is more prominent. Collectively, our results reveal the genetic diversity and evolutionary dynamics of lineage GI-7 IBVs, which could assist in the prevention and control of viral infection.

IntroductionNewcastle disease virus (NDV) is an important avian pathogen prevalent worldwide; it has an extensive host range and seriously harms the poultry industry. Velogenic NDV strains exhibit high pathogenicity and mortality in chickens. Circular RNAs (circRNAs) are among the most abundant and conserved eukaryotic transcripts. They are part of the innate immunity and antiviral response. However, the relationship between circRNAs and NDV infection is unclear.MethodsIn this study, we used circRNA transcriptome sequencing to analyze the differences in circRNA expression profiles post velogenic NDV infection in chicken embryo fibroblasts (CEFs). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were used to reveal significant enrichment of differentially expressed (DE) circRNAs. The circRNA- miRNA-mRNA interaction networks were further predicted. Moreover, circ-EZH2 was selected to determine its effect on NDV infection in CEFs.ResultsNDV infection altered circRNA expression profiles in CEFs, and 86 significantly DE circRNAs were identified. GO and KEGG enrichment analyses revealed significant enrichment of DE circRNAs for metabolism-related pathways, such as lysine degradation, glutaminergic synapse, and alanine, aspartic-acid, and glutamic-acid metabolism. The circRNA- miRNA-mRNA interaction networks further demonstrated that CEFs might combat NDV infection by regulating metabolism through circRNA-targeted mRNAs and miRNAs. Furthermore, we verified that circ-EZH2 overexpression and knockdown inhibited and promoted NDV replication, respectively, indicating that circRNAs are involved in NDV replication.ConclusionsThese results demonstrate that CEFs exert antiviral responses by forming circRNAs, offering new insights into the mechanisms underlying NDV-host interactions.