The SARS-CoV-2 Omicron variant sparked the largest wave of infections worldwide. Mainland China eased its strict COVID-19 measures in late 2022 and experienced two nationwide Omicron waves in 2023. Here, we investigated lineage distribution and virus evolution in Guangdong, China, 2022-2023 by comparing 5813 local viral genomes with the datasets from other regions of China and worldwide. Additionally, we conducted three large-scale serological surveys involving 1696 participants to measure their immune response to the BA.5 and XBB.1.9 before and after the corresponding waves. Our findings revealed the Omicron variants, mainly the BA.5.2.48 lineage, causing infections in over 90% of individuals across different age groups within a month. This rapid spread led to the establishment of widespread immunity, limiting the virus’s ability to further adaptive mutation and dissemination. While similar immune responses to BA.5 were observed across all age groups after the initial wave, children aged 3 to 11 developed a stronger cross immune response to the XBB.1.9 strain, possibly explaining their lower infection rates in the following XBB.1 wave. Reinfection with Omicron XBB.1 variant triggered a more potent neutralizing immune response among older adults. These findings highlight the impact of age-specific immune responses on viral spread in potential future waves. Release of the zero-COVID policy in China in late 2022 led to two large Omicron-driven waves of infection in 2023. Here, the authors analyze virus genomes and serology data from before and after the two waves and describe changes in virus lineage distribution and age-specific antibody responses.

Hand, Foot and Mouth Disease (HFMD) is a highly contagious viral illness primarily affecting children globally. A significant epidemiological transition has been noted in mainland China, characterized by a substantial increase in HFMD cases caused by non-Enterovirus A71 (EV-A71) and non-Coxsackievirus A16 (CVA16) enteroviruses (EVs). Our study conducts a retrospective examination of 36,461 EV-positive specimens collected from Guangdong, China, from 2013 to 2021. Epidemiological trends suggest that, following 2013, Coxsackievirus A6 (CVA6) and Coxsackievirus A10 (CVA10) have emerged as the primary etiological agents for HFMD. In stark contrast, the incidence of EV-A71 has sharply declined, nearing extinction after 2018. Notably, cases of CVA10 infection were considerably younger, with a median age of 1.8 years, compared to 2.3 years for those with EV-A71 infections, possibly indicating accumulated EV-A71-specific herd immunity among young children. Through extensive genomic sequencing and analysis, we identified the N136D mutation in the 2 A protein, contributing to a predominant subcluster within genogroup C of CVA10 circulating in Guangdong since 2017. Additionally, a high frequency of recombination events was observed in genogroup F of CVA10, suggesting that the prevalence of this lineage might be underrecognized. The dynamic landscape of EV genotypes, along with their potential to cause outbreaks, underscores the need to broaden surveillance efforts to include a more diverse spectrum of EV genotypes. Moreover, given the shifting dominance of EV genotypes, it may be prudent to re-evaluate and optimize existing vaccination strategies, which are currently focused primarily target EV-A71.

BACKGROUND:From 2022 to 2023, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused by Omicron variants spread rapidly in Guangdong Province, resulting in over 80% of the population being infected. RESULTS:To investigate the levels of neutralizing antibodies (NAbs) in individuals following the rapid pandemic and to evaluate the cross-protection against currently circulating variants of SARS-CoV-2 in China, neutralization assay and magnetic particle chemiluminescence method were used to test the 117 serum samples from individuals who had recovered 4 weeks post-infection. The results indicated that the levels of NAbs against prototype and Omicron variants BA.5 were significantly higher than those against Omicron variants BQ.1, XBB.1.1, XBB.1.9, XBB.1.16 and EG.5, regardless of whether the infection was primary or secondary. CONCLUSIONS:The cross-protection provided by NAbs induced by prototype and Omicron BA.5 variants was limited when challenged by BQ.1, XBB.1.1, XBB.1.9, XBB.1.16 and EG.5 variants. This indicates that we should pay more attention to the risk of multiple infection from any novel Omicron variants that may emerge in the near future.

Background: After the adjustment of COVID-19 epidemic policy, mainland China experienced two consecutive waves of Omicron variants within a seven-month period. In Guangzhou city, as one of the most populous regions, the viral infection characteristics, molecular epidemiology, and the dynamic of population immunity are still elusive. Methods: We launched a prospective cohort study in the Guangdong Provincial CDC from December 2022 to July 2023. Fifty participants who received the same vaccination regimen and had no previous infection were recruited. Results: 90% of individuals were infected with Omicron BA.5* variants within three weeks in the first wave. Thirteen cases (28.26%) experienced infection with XBB.1* variants, occurring from 14 weeks to 21 weeks after the first wave. BA.5* infections exhibited higher viral loads in nasopharyngeal sites compared to oropharyngeal sites. Compared to BA.5* infections, the XBB.1* infections had significantly milder clinical symptoms, lower viral loads, and shorter durations of virus positivity. The infection with the BA.5* variant elicited varying levels of neutralizing antibodies against XBB.1* among different individuals, even with similar levels of BA.5* antibodies. The level of neutralizing antibodies specific to XBB.1* determined the risk of reinfection. Conclusions: The rapid large-scale infections of the Omicron variants have quickly established herd immunity among the population in mainland China. In the future of the COVID-19 epidemic, a lower infection rate but a longer duration can be expected. Given the large population size and ongoing diversified herd immunity, it remains crucial to closely monitor the molecular epidemiology of SARS-CoV-2 for the emergence of new variants of concern in this region. Additionally, the timely evaluation of the immune status across different age groups is essential for informing future vaccination strategies and intervention policies.

Global COVID-19 vaccination programs effectively contained the fast spread of SARS-CoV-2. Characterizing the immunity status of returned populations will favor understanding the achievement of herd immunity and long-term management of COVID-19 in China. Individuals were recruited from 7 quarantine stations in Guangzhou, China. Blood and throat swab specimens were collected from participants, and their immunity status was determined through competitive ELISA, microneutralization assay and enzyme-linked FluoroSpot assay. A total of 272 subjects were involved in the questionnaire survey, of whom 235 (86.4%) were returning Chinese individuals and 37 (13.6%) were foreigners. Blood and throat swab specimens were collected from 108 returning Chinese individuals. Neutralizing antibodies against SARS-CoV-2 were detected in ~90% of returning Chinese individuals, either in the primary or the homologous and heterologous booster vaccination group. The serum NAb titers were significantly decreased against SARS-CoV-2 Omicron BA.5, BF.7, BQ.1 and XBB.1 compared with the prototype virus. However, memory T-cell responses, including specific IFN-γ and IL-2 responses, were not different in either group. Smoking, alcohol consumption, SARS-CoV-2 infection, COVID-19 vaccination, and the time interval between last vaccination and sampling were independent influencing factors for NAb titers against prototype SARS-CoV-2 and variants of concern. The vaccine dose was the unique common influencing factor for Omicron subvariants. Enhanced immunity against SARS-CoV-2 was established in returning Chinese individuals who were exposed to reinfection and vaccination. Domestic residents will benefit from booster homologous or heterologous COVID-19 vaccination after reopening of China, which is also useful against breakthrough infection.

Infection with severe acute respiratory syndrome coronavirus 2 Omicron variants still causes neurological complications in elderly individuals. However, whether and how aging brains are affected by Omicron variants in terms of neuroinvasiveness and neurovirulence are unknown. Here, we utilize resected paracarcinoma brain tissue from elderly individuals to generate primary brain spheroids (BSs) for investigating the replication capability of live wild-type (WT) strain and Omicron (BA.1/BA.2), as well as the mechanisms underlying their neurobiological effects. We find that both WT and Omicron BA.1/BA.2 are able to enter BSs but weakly replicate. There is no difference between Omicron BA.1/BA.2 and WT strains in neurotropism in aging BSs. However, Omicron BA.1/BA.2 exhibits ameliorating neurological damage. Transcriptional profiling indicates that Omicron BA.1/BA.2 induces a lower neuroinflammatory response than WT strain in elderly BSs, suggesting a mechanistic explanation for their attenuated neuropathogenicity. Moreover, we find that both Omicron BA.1/BA.2 and WT strain infections disrupt neural network activity associated with neurodegenerative disorders by causing neuron degeneration and amyloid-β deposition in elderly BSs. These results uncover Omicron-specific mechanisms and cellular immune responses associated with severe acute respiratory syndrome coronavirus 2-induced neurological complications.

Background Global COVID-19 vaccination programs effectively contain the fast spread of the SARS-CoV-2. Characteristic the immunity status of returned populations will favor for understanding the achievement of herd immunity and long-term management of COVID-19 in China. Methods Returning travellers were recruited from 7 quarantine stations in Guangzhou, China. The immunity statuses of participants were determined through Competitive ELISA, Micro-Neutralization Assay and Enzyme-Linked FluoroSpot Assay. Results A total of 272 subjects were involved in questionnaire survey, in which 235 (86.4%) were returning ex-patriot Chinese and 37 (13.6%) were foreigners. Blood and throat swabs specimens were collected from each of 108 returning ex-patriot Chinese. The neutralizing antibody against SARS-CoV-2 was detected in ~90% of returning ex-patriot Chinese, either in the primary or the homologous and heterologous booster vaccination group. The serum NAb titers of them were significantly decreased against SARS-CoV-2 Omicron BA.5, BF.7, BQ.1 and XBB.1 compare with prototype virus. However, memory T cell responses including specific IFN-γ and IL-2 were no differences in either group. Smoking, drinking, SARS-CoV-2 infection, COVID-19 vaccination, and the time interval between last vaccination and the sampling were independent influencing factors for NAb titers against prototype SARS-CoV-2 and variants of concerns. The dose of vaccination was the unique common influencing factor for Omicron variants. Conclusions The herd immunity was established in returning ex-patriot Chinese who exposure to the complicated infection and vaccination circumstance. Domestic residents will benefit from booster of COVID-19 vaccines either in homologous and heterologous vaccination after re-opening of China, as well as breakthrough infection.

We have read with interest in a recent study published in Gut by Weber et al, reporting abnormal elevation of gammaglutamyltransferase (37%) and total bilirubin (5%) in patients, that was associated with higher rates of COVID19related deaths. However, whether SARSCoV2 could infect human hepatocytes and cholangiocytes thus causing local damage has not been reported. Here, human organoids were used to investigate SARSCoV2 infection and its induced liver damage at cellular and molecular levels (figure 1A). We first established five lines of liver organoids and two lines of biliary organoids from adjacent normal tissues of seven patients with liver cancer (figure 1B; online supplemental figure 1A,B; online supplemental methods). We examined the susceptibility of human liver and biliary organoids to SARSCoV2 (Guangdong/20SF014/2020; EPI_ISL_403934; 19A) directly isolated from a patient with moderate COVID19. The expression of SARSCoV2 spike (S) glycoprotein protein was readily detected in patchy areas of human liver and biliary organoids, but not in uninfected control by immunofluorescence staining (figure 1C; online supplemental figure 1C). Viral load of SARSCoV2 was dramatically increased in liver (liver 1 to liver 4) and biliary organoids (biliary 1 and biliary 2) at 24 hours postinfection with SARSCoV2, which remained stable for 96 hours in liver organoids and 48 hours in biliary organoids (figure 1D; online supplemental figure 2A; online supplemental table S1). Meanwhile, we found that live SARSCoV2 could amplify in lysed organoids (liver 5) and its culture supernatant (figure 1E; online supplemental table S1), inferring human liver and biliary organoids are susceptible to SARSCoV2 and support robust viral replication. SARSCoV2 enters target cells mainly through the ACE2 receptor. Given that ACE2 receptor was more highly expressed in cholangiocytes (59.7%) than in hepatocytes (2.6%), we investigated the ultrastructure of SARSCoV2infected biliary organoids under transmission electron microscopes (TEM) and found that viral particles were present in the lumen and at basolateral and apical sides of the organoid, as well as in membranebound vesicles (figure 2A). Therefore, TEM captured the critical location of SARSCoV2 in infected biliary organoids, indicating potential dissemination route of how SARSCoV2 enters the cholangiocytes. Gene expression changes induced by SARSCoV2infection in liver and biliary organoids was identified by RNA sequencing. Heatmap and volcano plot of differentially expressed genes revealed robust induction of proinflammatory chemokines/cytokines including CXCL1 in SARSCoV2infected liver and biliary organoids. Consistently, KEGG Orthology Based Annotation System revealed multiple upregulated proinflammatory pathways in infected organoids, including NF-κB signalling pathway etc. Of note, the significant upregulation of TNF signalling pathway and apoptosis pathway in infection group indicated that SARSCoV2 infection may induce cell death of hepatocytes and cholangiocytes. Besides, UGT1A1 was upregulated in liver and biliary SARSCoV2infected organoids, which was associated with elevation of bilirubin. While, bile acid transporter gene SLCO4C1 was significantly decreased in SARSCoV2infected biliary organoid, and the steroid hormone biosynthesis and bile secretion pathways were upregulated in SARSCoV2infected organoids, which could cause bile acid accumulation. Moreover, the upregulation of IL1R2 and IL1RL1 could be associated with the albumin production inhibition, thereby impairing liver functions. It was reported an interacting host receptome of SARSCoV2 and demonstrated ASGR1 as alternative functional receptors, providing insight into SARSCoV2 tropism and pathogenesis. We found that ASGR1 was upregulated in infected liver organoids, which may explain that SARSCoV2 viral load was higher in liver organoids compared with biliary organoids, though expression of ACE2 receptor was upregulated in cholangiocytes than hepatocytes (figure 2B–E; online supplemental figure 2B; online supplemental table S1). Consistently, bilirubin levels were reported to be significantly higher in nonsurvivors than survivors with SARSCoV2 infection. 6 Immunohistochemistry further validated the upregulated expressions of inflammatory factor CXCL8 and CXCL11 in SARSCoV2infected biliary organoids Letter

The immunity of public health workers: observation from two waves SARS-CoV-2 Omicron variant endemic in Guangdong province, ChinaHuan Zhang1#, Lina Yi1#, Huifang Lin1#, Lirong Zou1, Pingping Zhou1, Chumin Liang1, Lilian Zeng1, Xue Zhuang1, Zhe Liu1, Jing Lu1, Jianfeng He1, Baisheng Li1*, Jiufeng Sun1,2,3,4,5*，Runyu Yuan1*.1Guangdong Workstation for Emerging Infectious Disease Control and Prevention, Guangdong Provincial Key Laboratory of Pathogen Detection for Emerging Infectious Disease Response, Guangdong Provincial Center for Disease Control and Prevention, Guangzhou 511430, China.

Enterovirus A71 (EV-A71) is a significant hand-foot-mouth disease (HFMD) etiology. The inactivated EV-A71 vaccines were approved in China in 2016. However, the seroprevalence of EV-A71 after the vaccine application and its potential association with the EV-A71 epidemic in the population are rarely studied. In this study, we analyzed the incidence of EV-A71 infection and seroepidemiology in Guangzhou City, China. From 2019 to 2021, 167,920 clinically confirmed HFMD cases were reported in Guangzhou. In 6,868 enterovirus-positive samples, Coxsackievirus A6 and Coxsackievirus A16 were dominant genotypes, and only 3 EV-A71-positive samples were detected, highlighting the deficient epidemic activity of EV-A71. Microneutralization assay was performed on 1,000 representative serum samples. Notably, the seroprevalence and geometric mean titer (GMT) decreased significantly in 2020, and that in the < 3-year age group were increased and even higher than that in 3–5-year age group in 2019 and 2021, which was contrary to our previous surveillance result and other studies in Guangzhou. Furthermore, a moderate decline of GMT level was observed following the vaccination, but the seropositive serums were still detected for 49 months after second immunization, suggesting the long-term persistence of the immunity. Our seroepidemiology study revealed relatively higher neutralizing antibody activity in the susceptible population after the EV-A71 vaccine was adopted in 2016 in Guangzhou. It may be one of the reasons for the lower epidemic activity of EV-A71 in Guangzhou from 2019 to 2021.

The SARS-CoV-2 Delta variant has spread rapidly worldwide. To provide data on its virological profile, we here report the first local transmission of Delta in mainland China. All 167 infections could be traced back to the first index case. Daily sequential PCR testing of quarantined individuals indicated that the viral loads of Delta infections, when they first become PCR-positive, were on average ~1000 times greater compared to lineage A/B infections during the first epidemic wave in China in early 2020, suggesting potentially faster viral replication and greater infectiousness of Delta during early infection. The estimated transmission bottleneck size of the Delta variant was generally narrow, with 1-3 virions in 29 donor-recipient transmission pairs. However, the transmission of minor iSNVs resulted in at least 3 of the 34 substitutions that were identified in the outbreak, highlighting the contribution of intra-host variants to population-level viral diversity during rapid spread.

A recent mutation analysis suggested that Non-Structural Protein 6 (NSP6) of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is a key determinant of the viral pathogenicity. Here, by transcriptome analysis, we demonstrated that the inflammasome-related NOD-like receptor signaling was activated in SARS-CoV-2-infected lung epithelial cells and Coronavirus Disease 2019 (COVID-19) patients’ lung tissues. The induction of inflammasomes/pyroptosis in patients with severe COVID-19 was confirmed by serological markers. Overexpression of NSP6 triggered NLRP3/ASC-dependent caspase-1 activation, interleukin-1β/18 maturation, and pyroptosis of lung epithelial cells. Upstream, NSP6 impaired lysosome acidification to inhibit autophagic flux, whose restoration by 1α,25-dihydroxyvitamin D 3 , metformin or polydatin abrogated NSP6-induced pyroptosis. NSP6 directly interacted with ATP6AP1, a vacuolar ATPase proton pump component, and inhibited its cleavage-mediated activation. L37F NSP6 variant, which was associated with asymptomatic COVID-19, exhibited reduced binding to ATP6AP1 and weakened ability to impair lysosome acidification to induce pyroptosis. Consistently, infection of cultured lung epithelial cells with live SARS-CoV-2 resulted in autophagic flux stagnation, inflammasome activation, and pyroptosis. Overall, this work supports that NSP6 of SARS-CoV-2 could induce inflammatory cell death in lung epithelial cells, through which pharmacological rectification of autophagic flux might be therapeutically exploited.

Background Southern China is at risk for arborvirus disease transmission, including Zika virus and dengue. Patients often present to clinical care with non-specific acute febrile illnesses (AFI). To better describe the etiology of AFI, we implemented a two-year AFI surveillance project at five sentinel hospitals in Yunnan and Guangdong Provinces. Methods Between June 2017 and August 2019, we enrolled patients between 2 and 65 years of age presenting at one sentinel hospital in Mengla County, Yunnan, and four in Jiangmen City, Guangdong, with symptoms of AFI (acute onset of fever ≥ 37.5°C within the past 7 days) without respiratory symptoms or diarrhea. Demographic, epidemiologic, and clinical information was obtained and entered into a web-based AFI surveillance database. A custom TaqMan Array card (TAC) was used to test patients’ whole blood specimens for 27 different pathogens using real-time polymerase chain reaction assays. Results During the two-year project period, 836 patients were enrolled; 443 patients from Mengla County and 393 patients from Jiangmen City. The median age was 33 years [range: 2–65], and most were hospitalized [641, 77%]. Of 796 patients with valid TAC results, 341 (43%) were positive for at least one of the 10 unique pathogens detected. This included 205 (26%) patients positive for dengue virus, 60 (8%) for Orientia tsutsugamushi, and 42 (5%) for Coxiella burnetii. Ten patients (1%) in Jiangmen City tested positive for malaria, 8 of whom reported recent travel outside of China. TAC results were negative for 455 (57%) patients. None of the patients had a positive TAC detection for Zika virus. Conclusions The project detected variability in the etiology of AFI in Southern China and highlighted the importance of differential diagnosis. Dengue, O. tsutsugamushi, and C. burnetii were the most frequently identified pathogens among enrolled AFI patients. As a non-notifiable disease, the frequent detection of C. burnetii is noteworthy and warrants additional investigation. The project provided a framework for routine surveillance for persons presenting with AFI.

Background: EV-A71 is a common causative agent of hand foot and mouth disease. In mainland China, EV-A71 subgenotype C4 has been the sole circulating genotype since 2008, and was used in the production of multiple licensed vaccines. Here, we report the first detection EV-A71 C1 strains in China. Methods: Full genomic sequence were obtained. The origin of the EV-A71 C1 strains were tracked down by Bayesian inferences. Recombination was analyzed using Simplot program. And the antigenicity were tested using the microneutralization test. Results: The C1-GD2019 shared high identity with the C1-like lineage recently identified in Europe and was introduced into Guangdong in 2018-2019. Close genetic relatedness between the C1-GD2019 and Europe C1-like strains were observed except for the 3D-3'UTR region. The late showed high similarity with CVA genomes. Antigenic variance was found. The C1-GD2019 could not be effectively neutralized by EV-A71 C4a neutralizing antibody positive samples. Conclusion: This is the first report of EV-A71 subgenotype C1 isolated in China. It is a recombinant strain originating from C1-like strains recently identified in Europe and CVA strains. The different antigenicity between the C1 strains and C4a vaccine strains highlighted the importance on closely monitoring the EV-A71 C1 strains in China. (C) 2020 Published by Elsevier Ltd on behalf of The British Infection Association.

探讨巨细胞病毒感染与住院严重急性呼吸道感染(SARI)肺炎的相关性.以67例符合严重急性呼吸系统感染临床诊断标准的住院病例为研究对象,同时以81例流感样门诊病例作为对照,使用荧光定量PCR方法检测所有研究对象的巨细胞病毒感染情况.采用二分类logistic回归模型分析巨细胞感染与住院严重急性呼吸道感染肺炎病例的关联.巨细胞病毒在呼吸道感染病例中有较高的阳性率,阳性率随年龄呈下降趋势.80％以上巨细胞病毒阳性病例存在与其他常见呼吸道病原共感染情况.Logistic回归分析表明:年龄和多病原共感染是SARI肺炎发生的危险因素,单独CMV阳性与SARI肺炎的发生没有显著相关性.SARI肺炎中CMV与其他呼吸道病原共感染概率高,临床上应加强对呼吸道感染病例的巨细胞病毒检测.

Noroviruses (NoVs) are the leading cause of acute gastroenteritis (AGE) outbreaks. Since 2014, novel genetic variants of NoV have been continuously identified and have caused a sharp increase in the number of AGE outbreaks. The specific geographical distribution and expanding genetic diversity of NoV has posed a challenge to conventional surveillance. Here, we describe the long-term dynamic correlation between NoV distribution in sewage and in the local population through the molecular surveillance of NoV in Guangdong, 2013-2018. The relative viral loads of the GI and GII genotypes in sewage were calculated through RT-PCR. A high-throughput sequencing method and operational taxonomic unit (OTU) clustering pipeline were developed to illustrate the abundances of different genotypes and genetic variants in sewage. Our results showed that the NoV viral loads and the emergence of new variants in sewage were closely associated with NoV outbreak risks in the population. Compared with the outbreaks surveillance, the dominance of the newly emerged variants, GII.P17-GII.17 and GII.P16-GII.2, could be detected one or two months ahead in sewage of a hub city. In addition, the dynamics of pre-epidemic variants, which were rarely detected in clinics, could be captured through sewage surveillance, thus improving our understanding of the origin and evolution of these novel epidemic variants. Our data highlight that sewage surveillance could provide nearly real-time and high-throughput data on NoV circulation in the community. With the advances in sequencing techniques, the sewage surveillance system could also be extended to other related infectious diseases.

Background HAdV infection can cause a variety of diseases. Although infections with HAdVs often are mild, life-threatening respiratory disease can occur. Pneumonia is one of the more serious types of HAdV-induced respiratory disease in children. In this study, we determined the prevalence and genotype of HAdVs among children hospitalized with pneumonia in Guangzhou, China. Methods Nasopharyngeal swabs (NPSs) were collected from children hospitalized with pneumonia in Guangzhou, China, from January 2013 to June 2019. HAdVs were detected by real-time polymerase chain reaction assay, and hexon, fiber, and penton gene were amplified and used for phylogenetic analysis. Epidemiological data were analyzed using SPSS16.0 software. Results and Conclusions A total of 1778 children hospitalized with pneumonia were enrolled. The overall HAdV detection rate was 3.26%. And the yearly detection rate varied from around 2.5% in 2013-2017 to around 6% in 2018-2019. Children >5 years had the highest HAdV infection rate. 92.86% of HAdV sequences obtained in this study were belonged to species B, and no recombination was observed. HAdV-B7 and HAdV-B3 were the common types detected in the study period, with the predominant HAdV genotype shifted from HAdV-B3 in 2015-2016 to HAdV-B7 in 2017-2018. The discrepancies in HAdV detection rates in different study period and changes of HAdV predominant types over time highlighted the importance of continued surveillance.

Objective:To understand the pathogenic spectrum and epidemiological characteristics of febrile respiratory syndrome in Guangdong province, and to provide reference for disease prevention, clinical diagnosis and treatment.Methods:The pathogens of 1 891 nasopharyngeal swabs collected from 2011 to 2018 were detected by real-time fluorescent polymerase chain reaction. The different rates were compared by chi-square test or Bonferronni method of comparison.Results:Among 1 891 samples, 810 samples were positive for viral nucleic acid, with a total detection rate of 42.78%. The main infectious agents were Parainfluenza virus (PIV), Rhinovirus (RhV) and Coronavirus(CoV). The pathogen detection rate was higher in <5 years group and 5~ years group. Pathogen detection in patients with different symptoms showed that the detection rate of Metapneumovirus (MPV) in pneumonia patients was relatively high. Influenza virus A (FluA), PIV, CoV and RhV had higher detection rate in patients without pneumonia. FLuA and Adenovirus (ADV)had a relatively high detection rate in the high and ultra-high fever groups. The detection rate of CoV and Mycoplasma pneumonia(MP) in moderate fever group was relatively high. The detection rate of PIV in cough patients was relatively high. The prevalence of several viruses has strong seasonality, and the detection rate was generally higher in winter and spring. Different virus detection rates also have strong regularity in years.Conclusions:PIV, RhV and CoV are the main pathogens of febrile respiratory syndrome in Guangdong in recent years.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a novel coronavirus first identified in December 2019. Notable features that make SARS-CoV-2 distinct from most other previously identified betacoronaviruses include a receptor binding domain and a unique insertion of 12 nucleotides or 4 amino acids (PRRA) at the S1/S2 boundary. In this study, we identified two deletion variants of SARS-CoV-2 that either directly affect the polybasic cleavage site itself (NSPRRAR) or a flanking sequence (QTQTN). These deletions were verified by multiple sequencing methods. In vitro results showed that the deletion of NSPRRAR likely does not affect virus replication in Vero and Vero-E6 cells; however, the deletion of QTQTN may restrict late-phase viral replication. The deletion of QTQTN was detected in 3 of 68 clinical samples and 12 of 24 in vitro-isolated viruses, while the deletion of NSPRRAR was identified in 3 in vitro-isolated viruses. Our data indicate that (i) there may be distinct selection pressures on SARS-CoV-2 replication or infection in vitro and in vivo; (ii) an efficient mechanism for deleting this region from the viral genome may exist, given that the deletion variant is commonly detected after two rounds of cell passage; and (iii) the PRRA insertion, which is unique to SARS-CoV-2, is not fixed during virus replication in vitro. These findings provide information to aid further investigation of SARS-CoV-2 infection mechanisms and a better understanding of the NSPRRAR deletion variant observed here. IMPORTANCE The spike protein determines the infectivity and host range of coronaviruses. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has two unique features in its spike protein, the receptor binding domain and an insertion of 12 nucleotides at the S1/S2 boundary resulting in a furin-like cleavage site. Here, we identified two deletion variants of SARS-CoV-2 that either directly affect the furin-like cleavage site itself (NSPRRAR) or a flanking sequence (QTQTN), and we investigated these deletions in cell isolates and clinical samples. The absence of the polybasic cleavage site in SARS-CoV-2 did not affect virus replication in Vero or Vero-E6 cells. Our data indicate the PRRAR sequence and the flanking QTQTN sequence are not fixed in vitro; thus, there appears to be distinct selection pressures on SARS-CoV-2 sequences in vitro and in vivo. Further investigation of the mechanism of generating these deletion variants and their infectivity in different animal models would improve our understanding of the origin and evolution of this virus.

In April 2019, a suspect cluster of enterovirus cases was reported in a neonatology department in Guangdong, China, resulting in five deaths. We aimed to investigate the pathogen profiles in fatal cases, the circulation and transmission pattern of the viruses by combining metatranscriptomic, phylogenetic, and epidemiological analyses. Metatranscriptomic sequencing was used to characterize the enteroviruses. Clinical and environmental surveillance in the local population was performed to understand the prevalence and genetic diversity of the viruses in the local population. The possible source(s), evolution, transmission, and recombination of the viruses were investigated by incorporating genomes from the current outbreak, from local retrospective surveillance, and from public databases. Metatranscriptomic analysis identified Echovirus 11 (E11) in three fatal cases. Seroprevalence of neutralization antibody to E11 was 35 to 44 per cent in 3-15 age groups of general population, and the viruses were associated with various clinical symptoms. From the viral phylogeny, nosocomial transmissions were identified and all E11 2019 outbreak strains were closely related with E11 strains circulating in local population 2017-19. Frequent recombination occurred among the 2019 Guangdong E11 outbreak strains and various genotypes in enterovirus B species. This study provides an example of combining advanced genetic technology and epidemiological surveillance in pathogen diagnosis, source(s), and transmission tracing during an infectious disease outbreak. The result highlights the hidden E11 circulation and the risk of viral transmission and infection in the young age population in China. Frequent recombination between Guangdong-like strains and other enterovirus genotypes also implies the prevalence of these emerging E11 strains.