Birds as reservoirs: unraveling the global spread of Gamma- and Deltacoronaviruses.

Avian migration is a global phenomenon that transcends geographical boundaries. These migratory birds serve as unwitting carriers of diverse Gammacoronaviruses (γ-CoVs) and Deltacoronaviruses (δ-CoVs). While recombination events have been documented among γ-CoVs in avian species and ß-CoVs in mammals, evidence for recombination between CoVs of distinct genera remains limited. This minireview examines the prevalence of CoVs in both domestic waterfowl (ducks and geese) and wild bird populations inhabiting various regions. We investigate the dissemination patterns of γ-CoVs and δ-CoVs among these populations, highlighting their shared characteristics. Furthermore, the review explores the intricate web of cross-species transmission of δ-CoVs from wild birds to mammals, with a particular focus on pigs. Understanding the distinct features of CoVs harbored by waterfowl and wild birds and their potential for cross-species transmission is crucial for preparedness and response to future CoV epidemics.

Immune responses induced by a recombinant C-strain of classical swine fever virus expressing the F317L protein of African swine fever virus.

African swine fever (ASF), a highly infectious and devastating disease affecting both domestic pigs and wild boars, owes its etiology to African swine fever virus (ASFV). ASFV encodes more than 165 proteins. However, novel immunogenic proteins remain unknown. This study aimed to determine the antigenicity of the F317L protein (pF317L) of ASFV. The results revealed that pF317L was able to react with convalescent pig sera, indicating that pF317L could be a candidate antigen. The antigenic potential of pF317L expressed by rHCLV-F317L, a recombinant virus in the backbone of C-strain (a lapinized live attenuated classical swine fever virus) was further investigated in rabbits and pigs. The results revealed that antibodies and cell-mediated immune responses against pF317L were induced in either rabbits or pigs inoculated with rHCLV-F317L. Importantly, anti-pF317L antibodies from rabbits or pigs immunized with rHCLV-F317L significantly inhibited ASFV replication in vitro. In conclusion, pF317L demonstrates favorable immunogenic properties, positioning it as a promising candidate for the development of protective antigens in the ongoing endeavor to formulate efficacious ASF vaccine strategies.

The H4 subtype of avian influenza virus: a review of its historical evolution, global distribution, adaptive mutations and receptor binding properties.

The H4 subtype of avian influenza virus (AIV) exhibits a wide host range and is commonly found in migratory waterfowl. Recent studies have revealed that the H4N6 AIV can infect guinea pigs via aerosol transmission without prior adaptation. Additionally, the Q226L/G228S substitutions in the receptor-binding site have led to structural changes in globular head of H4 AIV, resulting in a configuration similar to that of pandemic H2N2 and H3N2 human influenza viruses. This article provides an updated review of the historical evolution, global distribution, adaptive mutations, receptor-binding preferences, and host range of H4 AIV. The insights presented herein will help in assessing the potential risk of future H4 AIV epidemics.

Research progress of porcine epidemic diarrhea virus S protein.

Porcine epidemic diarrhea virus (PEDV) is a single-stranded RNA virus with a capsid membrane that causes acute infectious gastrointestinal disease characterized by vomiting, diarrhea, and dehydration in swine. Piglets are more susceptible to PEDV than adults, with an infection rate reaching 90% and a fatality rate as high as 100%. Moreover, PEDV has a rapid transmission rate and broad transmission range. Consequently, PEDV has caused considerable economic losses and negatively impacted the sustainability of the pig industry. The surface spike (S) glycoprotein is the largest structural protein in PEDV virions and is closely associated with host cell fusion and virus invasion. As such, the S protein is an important target for vaccine development. In this article, we review the genetic variation, immunity, apoptosis-induction function, virulence, vaccine potential, and other aspects of the PEDV S protein. This review provides a theoretical foundation for preventing and controlling PEDV infection and serves as a valuable resource for further research and development of PEDV vaccines.

Recent H9N2 avian influenza virus lost hemagglutination activity due to a K141N substitution in hemagglutinin.

The H9N2 avian influenza virus (AIV) represents a significant risk to both the poultry industry and public health. Our surveillance efforts in China have revealed a growing trend of recent H9N2 AIV strains exhibiting a loss of hemagglutination activity at 37°C, posing challenges to detection and monitoring protocols. This study identified a single K141N substitution in the hemagglutinin (HA) glycoprotein as the culprit behind this diminished hemagglutination activity. The study evaluated the evolutionary dynamics of residue HA141 and studied the impact of the N141K substitution on aspects such as virus growth, thermostability, receptor-binding properties, and antigenic properties. Our findings indicate a polymorphism at residue 141, with the N variant becoming increasingly prevalent in recent Chinese H9N2 isolates. Although both wild-type and N141K mutant strains exclusively target α,2-6 sialic acid receptors, the N141K mutation notably impedes the virus's ability to bind to these receptors. Despite the mutation exerting minimal influence on viral titers, antigenicity, and pathogenicity in chicken embryos, it significantly enhances viral thermostability and reduces plaque size on Madin-Darby canine kidney (MDCK) cells. Additionally, the N141K mutation leads to decreased expression levels of HA protein in both MDCK cells and eggs. These findings highlight the critical role of the K141N substitution in altering the hemagglutination characteristics of recent H9N2 AIV strains under elevated temperatures. This emphasizes the need for ongoing surveillance and genetic analysis of circulating H9N2 AIV strains to develop effective control and prevention measures.IMPORTANCEThe H9N2 subtype of avian influenza virus (AIV) is currently the most prevalent low-pathogenicity AIV circulating in domestic poultry globally. Recently, there has been an emerging trend of H9N2 AIV strains acquiring increased affinity for human-type receptors and even losing their ability to bind to avian-type receptors, which raises concerns about their pandemic potential. In China, there has been a growing number of H9N2 AIV strains that have lost their ability to agglutinate chicken red blood cells, leading to false-negative results during surveillance efforts. In this study, we identified a K141N mutation in the HA protein of H9N2 AIV to be responsible for the loss of hemagglutination activity. This finding provides insight into the development of effective surveillance, prevention, and control strategies to mitigate the threat posed by H9N2 AIV to both animal and human health.

Prevalence, genomic characteristics, and pathogenicity of fowl adenovirus 2 in Southern China.

In recent years, the occurrence of fowl adenovirus 2 (FAdV-2) has been on the rise in China, posing a significant threat to the poultry industry. This study aimed to investigate the epidemiology, phylogenetic relationship, genomic characteristics, and pathogenicity of FAdV-2. The epidemiological analysis revealed the detection of multiple FAdV serotypes, including FAdV-1, FAdV-2, FAdV-3, FAdV-4, FAdV-8a, FAdV-8b, and FAdV-11 serotypes. Among them, FAdV-2 exhibited the highest proportion, accounting for 21.05% (8/38). The complete genomes of these 8 FAdV-2 strains were sequenced. Genetic evolution analysis indicated that these FAdV-2 strains formed a separate branch within the FAdV-D group, sharing 94.60 to 97.90% nucleotide similarity with the reference FAdV-2 and FAdV-11 strains. Notably, the recombination analysis revealed that 5 out of the 8 FAdV-2 strains, exhibited recombination events between FAdV-2 and FAdV-11. The recombination regions involved Hexon, Fiber, ORF19 genes and 3' end. Furthermore, pathogenicity experiments demonstrated that recombinant FAdV-2 XX strain is capable of inducing mortality rate of 66.70% and causing more severe hepatitis hydropericardium syndrome (HHS) in 6-wk-old specific-pathogen-free chickens. These findings contribute to our understanding of the prevalence, genomic characteristics, and the pathogenicity of FAdV-2, providing foundations for FAdV-2 vaccine development.

Identification, pathological, and genomic characterization of novel goose reovirus associated with liver necrosis in geese, China.

Since 2021, a novel strain of goose reovirus (GRV) has emerged within the goose farming industry in Guangdong province, China. This particular viral variant is distinguished by the presence of white necrotic foci primarily localized in the liver and spleen, leading to substantial economic losses for the poultry industry. However, the etiology, prevalence and genomic characteristics of the causative agent have not been thoroughly investigated. In this study, we conducted an epidemiological inquiry employing suspected GRV samples collected from May 2021 to September 2022. The macroscopic pathological and histopathological lesions associated with GRV-infected clinical specimens were examined. Moreover, we successfully isolated the GRV strain and elucidated the complete genome sequence of the isolate GD21/88. Through phylogenetic and recombination analysis, we unveiled that the GRV strains represent a novel variant resulting from multiple reassortment events. Specifically, the µNS, λC, and σNS genes of GRV were found to have originated from chicken reovirus, while the σA gene of GRV exhibited a higher degree of similarity with a novel duck reovirus. The remaining genes of GRV were traced back to Muscovy duck reovirus. Collectively, our findings underscore the significance of GRV as a pathogenic agent impacting the goose farming industry. The insights gleaned from this study contribute to a more comprehensive understanding of the epidemiology of GRV in Southern China and shed light on the genetic reassortment events exhibited by the virus.

Development and application of a triplex real-time PCR assay for the detection of H3, H4, and H5 subtypes of avian influenza virus.

Avian influenza virus (AIV) poses a significant threat to the poultry industry and public health. Among the diverse AIV subtypes, H3, H4, and H5 are frequently detected in waterfowl and live poultry markets (LPM). The expeditious and precise identification of these subtypes is imperative in impeding the dissemination of the disease. In this study, we have developed a triplex real-time PCR assay endowed with the capacity to simultaneously discriminate AIV subtypes H3, H4, and H5. This method showcases remarkable specificity, selectively amplifying H3, H4, and H5 AIV subtypes sans any cross-reactivity with other subtypes or common avian pathogens. Furthermore, this method exhibits high sensitivity, with a detection threshold of 2.1 × 102 copies/µL for H3, H4, and H5 AIV subtypes. Additionally, the assay demonstrates reproducibility, as evidenced by intra- and interassay variability, with a coefficient of variation below 1.5%. A total of 338 cloacal swabs were collected from LPM to evaluate the performance of our assay. The obtained results evinced a high level of concordance with the sequencing data. In summary, our study has developed a triplex real-time PCR method that can be employed in laboratory-based testing and surveillance of AIV. This assay holds promise in augmenting our ability to detect and monitor AIV subtypes, thereby facilitating timely interventions and safeguarding both the poultry industry and public health.

The Prevalence and Genetic Diversity of Porcine Circoviruses (PCVs) during 2017-2023 in Guangdong Province, China.

Porcine circovirus disease poses a significant threat to the pig farming industry. Globally, four genotypes of porcine circovirus are circulating, with porcine circovirus type 2 and 3 (PCV2 and PCV3) being most strongly associated with clinical manifestations. The recently discovered porcine circovirus type 4 (PCV4) exhibits clinical symptoms resembling porcine dermatitis nephropathy syndrome. This study aimed to assess the prevalence and genetic characteristics of PCVs in Guangdong province, China. A comprehensive analysis was conducted on 193 samples collected from 83 distinct pig farms during the period of 2017-2023. A conventional PCR was employed to investigate the presence of PCV2, PCV3, and PCV4. Among the samples, 56.48%, 8.81%, and 8.81% tested positive for PCV2, PCV3, and PCV2/3 co-infection, respectively. Interestingly, PCV4 was not detected. Whole-genome sequencing was performed on 80 PCV2 isolates and 7 PCV3 isolates. A phylo-genetic analysis revealed that 12 strains belonged to PCV2a, 8 strains belonged to PCV2b, and 60 strains belonged to PCV2d, indicating the prevailing presence of PCV2d in Guangdong province, China. Furthermore, two PCV3 isolates were classified as PCV3a and five strains as PCV3b. Notably, an in-depth analysis of the Cap protein sequence of the PCV2 and PCV3 isolates identified high-frequency mutation sites located in predicted epitope regions. Overall, this study provides valuable insights into the prevalence and evolution of PCV2 and PCV3 during the period of 2017-2023 in Guangdong province, China, thereby contributing to the development of effective prevention and control measures.

Global distribution, receptor binding, and cross-species transmission of H6 influenza viruses: risks and implications for humans.

The H6 subtype of avian influenza virus (AIV) is a pervasive subtype that is ubiquitously found in both wild bird and poultry populations across the globe. Recent investigations have unveiled its capacity to infect mammals, thereby expanding its host range beyond that of other subtypes and potentially facilitating its global transmission. This heightened breadth also endows H6 AIVs with the potential to serve as a genetic reservoir for the emergence of highly pathogenic avian influenza strains through genetic reassortment and adaptive mutations. Furthermore, alterations in key amino acid loci within the H6 AIV genome foster the evolution of viral infection mechanisms, which may enable the virus to surmount interspecies barriers and infect mammals, including humans, thus posing a potential threat to human well-being. In this review, we summarize the origins, dissemination patterns, geographical distribution, cross-species transmission dynamics, and genetic attributes of H6 influenza viruses. This study holds implications for the timely detection and surveillance of H6 AIVs.

The MGF300-2R protein of African swine fever virus is associated with viral pathogenicity by promoting the autophagic degradation of IKKα and IKKß through the recruitment of TOLLIP.

The multigene family genes (MGFs) in the left variable region (LVR) of the African swine fever virus (ASFV) genome have been reported to be involved in viral replication in primary porcine alveolar macrophages (PAMs) and virulence in pigs. However, the exact functions of key MGFs in the LVR that regulate the replication and virulence of ASFV remain unclear. In this study, we identified the MGF300-2R gene to be critical for viral replication in PAMs by deleting different sets of MGFs in the LVR from the highly virulent strain ASFV HLJ/18 (ASFV-WT). The ASFV mutant lacking the MGF300-2R gene (Del2R) showed a 1-log reduction in viral titer, and induced higher IL-1ß and TNF-α production in PAMs than did ASFV-WT. Mechanistically, the MGF300-2R protein was found to interact with and degrade IKKα and IKKß via the selective autophagy pathway. Furthermore, we showed that MGF300-2R promoted the K27-linked polyubiquitination of IKKα and IKKß, which subsequently served as a recognition signal for the cargo receptor TOLLIP-mediated selective autophagic degradation. Importantly, Del2R exhibited a significant reduction in both replication and virulence compared with ASFV-WT in pigs, likely due to the increased IL-1ß and TNF-α, indicating that MGF300-2R is a virulence determinant. These findings reveal that MGF300-2R suppresses host innate immune responses by mediating the degradation of IKKα and IKKß, which provides clues to paving the way for the rational design of live attenuated vaccines to control ASF.

Receptor Binding Properties of Neuraminidase for influenza A virus: An Overview of Recent Research Advances.

Influenza A viruses (IAVs) pose a serious risk to both human and animal health. IAVs' receptor binding characteristics account for a major portion of their host range and tissue tropism. While the function of neuraminidase (NA) in promoting the release of progeny virus is well-known, its role in the virus entry process remains poorly understood. Studies have suggested that certain subtypes of NA can act as receptor-binding proteins, either alone or in conjunction with haemagglutinin (HA). An important distinction is that NA from the avian influenza virus have a second sialic acid-binding site (2SBS) that is preserved in avian strains but missing in human or swine strains. Those observations suggest that the 2SBS may play a key role in the adaptation of the avian influenza virus to mammalian hosts. In this review, we provide an update of the recent research advances in the receptor-binding role of NA and highlight its underestimated importance during the early stages of the IAV life cycle. By doing so, we aim to provide new insights into the mechanisms underlying IAV host adaptation and pathogenesis.

Characterization and pathogenicity evaluation of recombinant novel duck reovirus isolated from Southeast China.

The novel duck reovirus (NDRV) emerged in southeast China in 2005. The virus causes severe liver and spleen hemorrhage and necrosis in various duck species, bringing serious harm to waterfowl farming. In this study, three strains of NDRV designated as NDRV-ZSS-FJ20, NDRV-LRS-GD20, and NDRV-FJ19 were isolated from diseased Muscovy ducks in Guangdong and Fujian provinces. Pairwise sequence comparisons revealed that the three strains were closely related to NDRV, with nucleotide sequence identities for 10 genomic fragments ranging between 84.8 and 99.8%. In contrast, the nucleotide sequences of the three strains were only 38.9-80.9% similar to the chicken-origin reovirus and only 37.6-98.9% similar to the classical waterfowl-origin reovirus. Similarly, phylogenetic analysis revealed that the three strains clustered together with NDRV and were significantly different from classical waterfowl-origin reovirus and chicken-origin reovirus. In addition, the analyses showed that the L1 segment of the NDRV-FJ19 strain was a recombinant of 03G and J18 strains. Experimental reproduction of the disease showed that the NDRV-FJ19 strain was pathogenic to both ducks and chickens and could lead to symptoms of hemorrhage and necrosis in the liver and spleen. This was somewhat different from previous reports that NDRV is less pathogenic to chickens. In conclusion, we speculated that the NDRV-FJ19 causing duck liver and spleen necrosis is a new variant of a duck orthoreovirus that is significantly different in pathogenicity from any previously reported waterfowl-origin orthoreovirus.

An ultrasensitive electrochemical sensor for detecting porcine epidemic diarrhea virus based on a Prussian blue-reduced graphene oxide modified glassy carbon electrode.

This study developed a novel, ultrasensitive sandwich-type electrochemical immunosensor for detecting the porcine epidemic diarrhea virus (PEDV). By electrochemical co-deposition of graphene and Prussian blue, a Prussian blue-reduced graphene oxide-modified glassy carbon electrode was made, further modified with PEDV-monoclonal antibodies (mAbs) to create a new PEDV immunosensor using the double antibody sandwich technique. The electrochemical characteristics of several modified electrodes were investigated using cyclic voltammetry (CV). We optimized the pH levels and scan rate. Additionally, we examined specificity, reproducibility, repeatability, accuracy, and stability. The study indicates that the immunosensor has good performance in the concentration range of 1 × 101.88 to 1 × 105.38 TCID50/mL of PEDV, with a detection limit of 1 × 101.93 TCID50/mL at a signal-to-noise ratio of 3σ. The composite membranes produced via co-deposition of graphene and Prussian blue effectively increased electron transport to the glassy carbon electrode, boosted response signals, and increased the sensitivity, specificity, and stability of the immunosensor. The immunosensor could accurately detect PEDV, with results comparable to real-time quantitative PCR. This technique was applied to PEDV detection and served as a model for developing additional immunosensors for detecting hazardous chemicals and pathogenic microbes.

Pathological and Molecular Characterization of a Duck Plague Outbreak in Southern China in 2021.

Duck plague (DP) is a highly contagious viral disease in ducks caused by the duck plague virus (DPV). The DPV, a member of Herpesviridae, poses a severe threat to the waterfowl farming industry worldwide. In this study, we reported a recent outbreak of DPV in domestic laying ducks at 310 days of age from southern China in December 2021. The gross lesion, histopathologic examination, molecular detection, and genetic characterization studies of DPV are described here. As a result, gross lesions such as an enlarged congestive spleen and liver were observed. Liver with vacuolar degeneration and small vacuoles and spleen with hemosiderosis were remarkable microscopic findings. Our results suggested that the liver had the highest viral load, followed by the trachea, pancreas, kidney, brain, spleen, and heart. In addition, DPV was successfully isolated in chicken embryo fibroblast cell culture and designated as DP-GD-305-21. The UL2, UL12, UL41, UL47, and LORF11 genes of DP-GD-305-21 shared a high nucleotide homology with the Chinese virulent (CHv) strain and the Chinese variant (CV) strain. In conclusion, this study reports the isolation and molecular characterization of DPV from a recent outbreak in southern China. Our results contributed to the understanding of the pathological and molecular characterization of currently circulating DPV in China.

Difference analysis of intestinal microbiota and metabolites in piglets of different breeds exposed to porcine epidemic diarrhea virus infection.

The gut microbial composition of the Luchuan (LC) piglet, one of China's native breeds, has rarely been studied, especially when compared to other breeds. This study developed a porcine epidemic diarrhea virus (PEDV) infection model in LC and Largewhite (LW) piglets, and analyzed the patterns and differences of intestinal microbial communities and metabolites in piglets of these two breeds after infection. The diarrhea score, survival time, and distribution of viral antigens in the intestine of piglets infected with PEDV differed among breeds, with the jejunal immunohistochemistry score of LW piglets being significantly higher than that of LC piglets (P < 0.001). The results of 16S rRNA sequencing showed differences in microbial diversity and community composition in the intestine of piglets with different breeds between PEDV infection piglets and the healthy controls. There were differences in the species and number of dominant phyla and dominant genera in the same intestinal segment. The relative abundance of Shigella in the jejunum of LC piglets after PEDV infection was significantly lower than that of LW piglets (P < 0.05). The key microorganisms differed in the microbiota were Streptococcus alactolyticus, Roseburia faecis, Lactobacillus iners, Streptococcus equi, and Lactobacillus mucosae (P < 0.05). The non-targeted metabolite analysis revealed that intestinal metabolites showed great differences among the different breeds related to infection. Spearman correlation analysis was conducted to examine any links between the microbiota and metabolites. The metabolites in the intestine of different breeds related to infection were mainly involved in arginine biosynthesis, synaptic vesicle cycle, nicotinic acid and nicotinamide metabolism and mTOR signaling pathway, with significantly positive or negative correlations (P < 0.05) between the various microorganisms. This study provides a theoretical foundation for investigating the application of core microorganisms in the gut of piglets of different breeds in the digestive tracts of those infected with PEDV, and helps to tackle the antimicrobial resistance problem further.

The 24.5-kb Left Variable Region Is Not a Determinant for African Swine Fever Virus to Replicate in Primary Porcine Alveolar Macrophages.

African swine fever (ASF) is a widespread hemorrhagic and highly contagious infectious disease caused by African swine fever virus (ASFV), currently threatening the pig industry worldwide. Here, we demonstrated that the cell-adapted strain ASFV-P121 with a 24.5-kb deletion in the left variable region (LVR) lost the ability to replicate in primary porcine alveolar macrophages (PAMs). To explore whether this deletion determines the inability of ASFV-P121 replication in PAMs, a mutant virus (ASFV-ΔLVR) with the same LVR deletion as ASFV-P121 was constructed based on the wild-type ASFV HLJ/18 (ASFV-WT). However, the growth titer of ASFV-ΔLVR only reduced 10-fold compared with ASFV-WT in PAMs. Furthermore, we found that the large deletion of the LVR does not affect the formation of virus factories and virion morphogenesis. These findings reveal important implications for analyzing the molecular mechanism of ASFV cell tropism change.

The first complete genome sequence and pathogenicity characterization of fowl adenovirus serotype 2 with inclusion body hepatitis and hydropericardium in China.

Since 2015, fowl adenovirus (FAdV) has been frequently reported worldwide, causing serious economic losses to the poultry industry. In this study, a FAdV-2, namely GX01, was isolated from liver samples of chickens with hepatitis and hydropericardium in Guangxi Province, China. The complete genome sequence of GX01 was determined about 43,663 base pairs (bp) with 53% G+C content. To our knowledge, this is the first FAdV-2 complete genome in China. There was a deleting fragment in ORF25 gene. Phylogenetic analysis based on the hexon loop-1 gene showed that GX01 is most closely related to FAdV-2 strain 685. Pathogenicity experiment of GX01 in 3-day-old and 10-day-old specific-pathogen-free chickens showed that although no mortality was observed within 21 days post infection (dpi), strain GX01 significantly inhibited weight gain of infected chickens. Moreover, FAdV-2 was still detectable in the anal swabs of infected chickens at 21 dpi. Necropsy analysis showed that the main lesions were observed in liver, heart, and spleen. Of note, hepatitis and hydropericardium were observed in the infected chickens. In addition, massive necrosis of lymphocyte was observed in spleen of infected 3-days-old chickens. We concluded that FAdV-2 strain GX01 is capable of causing hepatitis and hydropericardium, which will make serious impact on the growth of chickens. Our research lays a foundation to investigate the molecular epidemiology and etiology of FAdV.

Detection and genetic characterization of novel infectious bronchitis viruses from recent outbreaks in broiler and layer chicken flocks in southern China, 2021.

Avian infectious bronchitis virus (IBV) is a prevalent RNA virus that causes respiratory distress, nephritis, salpingitis, and egg production decline in chickens, resulting in significant economic loss. IBV is composed of complex genotypes and serotypes, which poses a great challenge for disease control. The current study reports 2 IBV outbreaks which were characterized by respiratory symptoms in IBV vaccinated commercial broilers and layers in Guangdong, China, in 2021. Two IBV strains, ZH01 and HH09, were identified via a RT-PCR assay through targeting the N gene and further characterization through full-length spike (S) gene sequence analysis. Phylogenetic analysis of S1 gene revealed that both ZH01 and HH09 belonged to the GI-19 lineage but contained a certain genetic distance from the GI-19 strain. Of note, the ZH01 and HH09 strains share a low homology of 70 and 86%, respectively, with common vaccine strains (H120), resulting in low vaccine protection. Further recombination analysis based on the S1 sequence suggested the newly identified IBV strains emerged through an intragroup recombination events between CK/CH/SCDY2003-2 and I0305/19 from G1-19 lineage. In addition, a number of novel mutations such as T273I, T292A, and S331K were found in the emerging IBV strains. Taken together, this study reports the genetic characteristics of 2 recent IBV outbreaks in southern China and emphasizes the urgent need for enhanced surveillance and development of novel vaccines for the control of IBV.