2018年杭州市登革热流行病学及病原特征研究

目的:了解2018年杭州市登革热疫情的流行病学及病原特征。方法:应用RT-PCR方法检测血清标本中的登革病毒核酸及其型别,并对阳性标本进行病毒分离、 E基因扩增、序列测定及进化分析;描述病例的时间、人群和地区分布特征。 结果:2018年杭州市共检测登革热病例80例,其中输入性病例55例,本地病例2...     

Molecular Characterisation and Phylogenetic Analysis of Dengue Outbreak in Pasighat,Arunachal Pradesh,Northeast India

Background and Objectives: Dengue is one of the most prevalent arboviral diseases in the world with 390 million dengue infections per year. In this study, we report the molecular characterisation of dengue outbreak in Pasighat, Arunachal Pradesh, Northeast India during 2015. Subjects and Methods: A total of 613 dengue-suspected cases were screened for dengue virus by dengue NS1 Ag and anti-dengue IgM antibody depending on the duration of sample collection and onset of symptom. Further, molecular characterisation was done by amplifying the C-PrM region by real-time polymerase chain reaction followed by phylogenetic analysis. Results: Molecular characterisation revealed that the dengue outbreak was predominantly due to dengue virus serotype-1 (DENV-1) (90.9%) while DENV-2 was detected in 7.5% of samples. Co-infection of DENV-1 and DENV-2 was detected in one case. Phylogenetic analysis of the DENV-1 strains with the prototype revealed that the DENV-1 strains were grouped within genotype III. Similarly, DENV-2 strains were clustered within genotype IV. The study revealed a change in the predominant serotype in recent years with DENV-3 in 2012 to DENV-1, 2, 3 and 4 in 2014 to DENV-1 in 2015 in the study region. A unique L24M mutation was observed in the DENV-1 strains of Arunachal Pradesh which was absent in all the circulating strains in India except one strain from the state of Kerala in South India. Marked variation within the DENV-2 strains was observed at A102V and I163V in one strain similar to earlier circulating isolates in India. Conclusions: The present study reveals a shift in the serotype dominance in the study region. As serotype shifts and secondary infection with a heterologous DENV serotype are frequently associated with disease severity, there is an urgent need for sustained monitoring of the circulating serotypes and enhanced surveillance operations, especially in the monsoon and post-monsoon periods to prevent large-scale, severe dengue outbreaks in this region.     

Phylogenetic and evolutionary analyses of dengue viruses isolated in Jakarta,Indonesia

Dengue has affected Indonesia for the last five decades and become a major health problem in many cities in the country. Jakarta, the capital of Indonesia, reports dengue cases annually, with several outbreaks documented. To gain information on the dynamic and evolutionary history of dengue virus (DENV) in Jakarta, we conducted phylogenetic and evolutionary analyses of DENV isolated in 2009. Three hundred thirty-three dengue-suspected patients were recruited. Our data revealed that dengue predominantly affected young adults, and the majority of cases were due to secondary infection. A total of 171 virus isolates were successfully serotyped. All four DENV serotypes were circulating in the city, and DENV-1 was the predominant serotype. The DENV genotyping of 17 isolates revealed the presence of Genotypes I and IV in DENV-1, while DENV-2 isolates were grouped into the Cosmopolitan genotype. The grouping of isolates into Genotype I and II was seen for DENV-3 and DENV-4, respectively. Evolutionary analysis revealed the relatedness of Jakarta isolates with other isolates from other cities in Indonesia and isolates from imported cases in other countries. We revealed the endemicity of DENV and the role of Jakarta as the potential source of imported dengue cases in other countries. Our study provides genetic information regarding DENV from Jakarta, which will be useful for upstream applications, such as the study of DENV epidemiology and evolution and transmission dynamics.     

Letter to the editor: molecular genotyping of Dengue Virus Types 2 and 4 from the Guatemalan and Honduran Epidemics of 2007 using the envelope glycoprotein gene

Eight serum specimens collected from dengue patients in Guatemala and Honduras during the Central American epidemic of 2007 were analyzed. Virus identification and serotyping performed by a nested RT-PCR assay revealed two DENV-1 isolates from Guatemala, four DENV-2 isolates, two each from Guatemala and Honduras, and two DENV-4 isolates from Honduras. Viral genotyping determined by phylogenetic analysis of the complete envelope gene sequences demonstrated that the DENV-2 isolates from Guatemala and Honduras fell into the American/Asian Genotype III, and were most closely related to DENV-2/NI/BID-V2683-1999 isolated from a dengue case in Nicaragua in 1999; and the DENV-4 F07-076 isolate from Honduras belonged to genotype II, and was most closely related to DENV-4/US/BID-V1093/1998 isolated from Puerto Rico in 1998. Our results suggest that the 2007 dengue outbreaks in Guatemala and Honduras were most likely caused by the re-emergence of earlier, indigenous DENV strains rather than by newly introduced strains and there were at least three serotypes of DENV co-circulating during the 2007 Central American epidemics.     

The whole-genome sequencing of prevalent DENV-1 strains during the largest dengue virus outbreak in Xishuangbanna Dai autonomous prefecture in 2019

In 2019, a serious dengue virus (DENV) infection broke out in the Xishuangbanna Dai Autonomous Prefecture, China. Therefore, we conducted a molecular epidemiological analysis in people that contracted DENV serotype 1 (DENV-1) during this year. We analyzed the molecular epidemiology of six DENV-1 epidemic strains in 2019 by full-length genome sequencing, amino acid mutation site analysis, evolutionary tree analysis, and recombination site comparison analysis. Through the analysis of amino acid mutation sites, it was found that DENV-1 strain (MW386867) was different from the other five epidemic DENV-1 strains in Xishuangbanna in 2019. MW386867 had unique mutation sites at six loci. The six epidemic DENV-1 strains in Xishuangbanna in 2019 were divided into two clusters. MW386867 was highly similar to the MG679800 (Myanmar 2017), MG679801 (Myanmar 2017), and KC172834 (Laos 2008), and the other five strains were highly similar to JQ045660 (Vietnam 2011), FJ176780 (GuangDong 2006). Genetic recombination analysis revealed that there was no recombination signal in the six epidemic DENV-1 strains in Xishuangbanna in 2019. We speculate that the DENV-1 epidemic in 2019 has a co-epidemic of local strains and cross-border strains.     

A retrospective survey of dengue virus infection in fatal cases from an epidemic in Brazil

Dengue virus can infect many cell types from the vascular, muscular and hematological systems causing diverse clinical and pathological signs. The purpose of the present study was to investigate by different diagnostic methods dengue virus in human tissue specimens obtained from fatal cases (n=29) during a large-scale dengue fever epidemic in 2002 in the State of Rio de Janeiro, Brazil. The combination of four procedures provided diagnostic confirmation of DENV-3 infection in 26 (89.6%) out of the 29 suspected fatal cases. Dengue virus (DENV) was isolated from 2/74 (2.7%) tissue samples, inoculated into C6/36 cells and identified as DENV-3, nested RT-PCR accusing 22/72 (30.5%) samples as DENV-3. Real-time RT-PCR yielded the highest positivity rate, detecting viral RNA in 45/77 (58.4%) clinical specimens, including the liver (n=18), lung (n=8), spleen (n=8), brain (n=6), kidney (n=3), bone marrow (n=1) and heart (n=1). Immunohistochemical tests recognized the DENV antigen in 26/59 (44%) specimens. Given the accuracy and effectiveness of real-time RT-PCR in this investigation, this approach may play an important role for rapid diagnosis of dengue infections.     

Genomic analysis of dengue virus serotype 1 (DENV-1) genotypes from Surabaya,Indonesia

Dengue has caused a significant public health impact globally. With the diverse genetic of the causative viruses, analysis of dengue virus (DENV) genomes is important to supplement epidemiological data with information that can be used to reconstruct the history of epidemics in time and space. We have reported the clinical and virological characteristics of dengue in Surabaya, Indonesia and revealed the presence of all four DENV serotypes and the predominance of DENV-1. The further classification of Surabaya DENV-1 into two different genotypes warrants in-depth genomic analysis to study the dynamics of both genotypes and their contribution to virus evolution, virus transmission, and disease. We performed full-length genome sequencing to nine isolates’ representatives from DENV-1 Genotype I and Genotype IV. Phylogenetic and evolutionary analyses suggested the more recent introduction of Genotype I viruses compared to the more endemic Genotype IV. Comparative analysis of Surabaya DENV-1 genomes and other sequences available publicly revealed that the majority of the DENV-1 codons were under strong purifying selection, while seven codon sites identified to be under positive selection. We highlight a unique codon site under the positive pressure in the NS1 gene of DENV-1. Our results provide additional genomic data of DENV from Indonesia that may contribute to the better understanding of dengue disease dynamics.     

Dengue in Rio Grande do Sul,Brazil: 2014 to 2016

The first autochthonous dengue case in Rio Grande do Sul (RS), Southern Brazil, occurred in 2007. In 2008 and 2009, only imported cases were reported in RS, but from 2010 to 2013, reports of autochthonous infections increased significantly. This study analyzes and discusses laboratory, demographic, and clinical data regarding dengue cases in RS, from 2014 to 2016. This study analyzed 13,420 serum samples from notified patients with suspicion of dengue fever in RS from 2014 to 2016. Seasonality of positive cases, viral serotypes, and clinical and epidemiological aspects were analyzed. There was no difference in gender (P = .4); dengue fever occurred mainly in adults, with similar distribution among age groups. The number of dengue virus (DENV) cases increased from 89 cases in 2014 to 2518 in 2016. Dengue virus 1 was the most prevalent circulating serotype during this period (97.5% of cases). Dengue virus infections show peaks in March and April (late summer and early autumn), after periods of high temperatures and rainfall. In 2014, dengue cases were concentrated in the northwestern and eastern regions of RS, and in 2015 and 2016, the northern region also confirmed a high number of cases. With increase in DENV circulation in RS, a rise in the number of autochthonous infections was also observed, mainly in highly urbanized areas. This study revealed that circulation of DENV in RS increased significantly in 2015 and 2016, with a rise in the number of autochthonous infections and cocirculation with Chikungunya and Zika viruses, recently introduced into RS.     

Isolation of dengue serotype 3 virus from the cerebrospinal fluid of an encephalitis patient in Hai Phong,Vietnam in 2013

Dengue encephalitis (DE) is characterized as unusual presentation of dengue infection. Despite the reports that DE accounts for only 1–5% of dengue cases, this disease tends to be increasingly reported to threaten global human health throughout dengue endemic areas particularly in Southeast Asia. The molecular information of clinically characterized, neurotropic dengue virus (DENV) in human beings is extremely scarce despite it playing an important role in deciphering the pathogenesis of dengue-related neurological cases. Here we report a case of DE caused by DENV3 genotype III in a male patient with atypical symptoms of DENV infection in Hai Phong, Vietnam in 2013. The virus isolated from the cerebrospinal fluid of this case-patient was closely related to DENV3 genotype III strains isolated from serum of two other patients, who manifested classical dengue in the same year and residing in the same area as the case-patient. It is noteworthy to mention that in 2013, DENV3 genotype III was detected for the first time in Vietnam.     

Subversion of early innate antiviral responses during antibody-dependent enhancement of Dengue virus infection induces severe disease in immunocompetent mice

Dengue is a mosquito-borne disease caused by one of four serotypes of Dengue virus (DENV-1–4). Epidemiologic and observational studies demonstrate that the majority of severe dengue cases, dengue hemorrhagic fever and dengue shock syndrome (DHF/DSS), occurs predominantly in either individuals with cross-reactive immunity following a secondary heterologous infection or in infants with primary DENV infections born from dengue-immune mothers, suggesting that B-cell-mediated and antibody responses impact on disease evolution. We demonstrate here that B cells play a pivotal role in host responses against primary DENV infection in mice. After infection, μMT^?/? mice showed increased viral loads followed by severe disease manifestation characterized by intense thrombocytopenia, hemoconcentration, cytokine production and massive liver damage that culminated in death. In addition, we show that poly and monoclonal anti-DENV-specific antibodies can sufficiently increase viral replication through a suppression of early innate antiviral responses and enhance disease manifestation, so that a mostly non-lethal illness becomes a fatal disease resembling human DHF/DSS. Finally, treatment with intravenous immunoglobulin containing anti-DENV antibodies confirmed the potential enhancing capacity of subneutralizing antibodies to mediate virus infection and replication and induce severe disease manifestation of DENV-infected mice. Thus, our results show that humoral responses unleashed during DENV infections can exert protective or pathological outcomes and provide insight into the pathogenesis of this important human pathogen.     

Imported dengue from 2013 Angola outbreak: Not just serotype 1 was detected

BackgroundAll the reports from Angola’s 2013 dengue outbreak revealed serotype 1. However, previously dengue serotypes 1–4 have been reported in Africa and in 2014 serotype 4 was reported in Angola.ObjectivesTo report dengue serotypes in patients returning from Angola during 2013 outbreak.Study designRetrospective, cross-sectional study. We serotyped the dengue by an in house Polymerase Chain Reaction technique in randomly selected cases.ResultsFrom the 2013 Angola’s dengue outbreak we treated 47 adult patients. None had history of past dengue. A combo kit test for dengue revealed positive NS1 antigen in 39 and IgM antibodies in 8. From 17 randomly patients tested by RNA Real Time-PCR, 11 were positive: 7 for DENV-1, 2 for DENV-2, 1 for DENV-3 (co-infected with DENV-1) and 1 for DENV-4. None had a complicated or fatal evolution.ConclusionUnlike previous reports the 4 serotypes were detected, and this resulted in a different epidemiological situation, raising the risk of future outbreaks of severe dengue.     

Natural attenuation of dengue virus type-2 after a series of island outbreaks: A retrospective phylogenetic study of events in the South Pacific three decades ago

Dengue is an expanding arboviral disease of variable severity characterized by the emergence of virus strains with greater fitness, epidemic potential and possibly virulence. To investigate the role of dengue virus (DENV) strain variation on epidemic activity we studied DENV-2 viruses from a series of South Pacific islands experiencing outbreaks of varying intensity and clinical severity. Initially appearing in 1971 in Tahiti and Fiji, the virus was responsible for subsequent epidemics in American Samoa, New Caledonia and Niue Island in 1972, reaching Tonga in 1973 where there was near-silent transmission for over a year. Based on whole-genome sequencing and phylogenetic analysis on 20 virus isolates, Tonga viruses were genetically unique, clustering in a single clade. Substitutions in the pre-membrane (prM) and nonstructural genes NS2A and NS4A correlated with the attenuation of the Tongan viruses and suggest that genetic change may play a significant role in dengue epidemic severity.     

Potential of ancestral sylvatic dengue-2 viruses to re-emerge

Dengue viruses (DENV) are the most important arboviral pathogens in tropical and subtropical regions throughout the world. DENV transmission includes both a sylvatic, enzootic cycle between nonhuman primates and arboreal mosquitoes of the genus Aedes, and an urban, endemic/epidemic cycle between Aedes aegypti, a mosquito with larval development in peridomestic water containers, and human reservoir hosts. All 4 serotypes of endemic DENV evolved independently from ancestral sylvatic viruses and have become both ecologically and evolutionarily distinct; this process may have involved adaptation to (i) peridomestic mosquito vectors and/or (ii) human reservoir hosts. To test the latter hypothesis, we assessed the ability of sylvatic and endemic DENV-2 strains, representing major genotypes from Southeast Asia, West Africa and the Americas, to replicate in two surrogate human model hosts: monocyte-derived, human dendritic cells (moDCs), and mice engrafted with human hepatoma cells. Although the various DENV-2 strains showed significant inter-strain variation in mean replication titers in both models, no overall difference between sylvatic and endemic strains was detected in either model. Our findings suggest that emergence of endemic DENV strains from ancestral sylvatic strains may not have required adaptation to replicate more efficiently in human reservoir hosts, implying that the potential for re-emergence of sylvatic dengue strains into the endemic cycle is high. The shared replication profiles of the American endemic and sylvatic strains suggest that American strains have maintained or regained the ancestral phenotype.     

Molecular epidemiology of dengue virus serotypes 2 and 3 in Paraguay during 2001-2006: the association of viral clade introductions with shifting serotype dominance

To determine the genetic variability of dengue viruses (DENVs) in Paraguay, the complete envelope gene was sequenced for 4 DENV-2 and 22 DENV-3 strains isolated from 2001 to 2006. The sequence data were used in Bayesian phylogenetic analyses, which revealed that Paraguayan DENV-2 strains fell into two distinct clades within the American/Asian genotype, thus suggesting that the introduction of a new DENV-2 clade was likely associated with the shift of dominant serotype from DENV-3 to DENV-2 in 2005 and might have caused an outbreak of DENV-2. This study also indicated that DENV-3 strains fell into genotype III, of which, several 2006 isolates varied from the remaining isolates in their tree locations. The introduction of this new clade was likely associated with the shift of dominant serotype from DENV-2 to DENV-3 in 2006 and might have caused an epidemic of DENV-3. More data are needed to test this hypothesis.     

Dengue virus serotypes and genotypic characterization from northeast India

Dengue is a rapidly spreading acute arboviral infection transmitted through a human and Aedes mosquito cycle. Though northeast region of India has been experiencing dengue outbreaks regularly for over a decade, reports on genetic characterization of the virus from this region are limited. The present study was undertaken to detect the genotype and genetic composition of circulating dengue virus (DENV) in this region. Blood samples were collected from 918 suspected dengue patients of five northeast Indian states. Serological investigations, viz, nonstructural 1 (NS1) enzyme-linked immunosorbent assay (ELISA), immunoglobulin M (IgM) ELISA, and immunoglobulin G (IgG) ELISA were performed followed by molecular detection. Sequence analysis and phylogenetic tree construction based on capsid-premembrane (C-prM) gene junction was done by BioEdit and MEGA6 software, respectively. Serological detection showed 35.34% NS1 and 18.12% IgM positivity. Secondary infection was observed in 24.53%. All four serotypes were detected. Phylogenetic analysis demonstrated circulation of genotype III of DENV-1, genotype IV of DENV-2, and genotype III of DENV-3. Sequences from this region form distinct clades in the phylogenetic tree. Characterization of the C-prM gene junction reveals divergence among the DENV strains. As genetic variation within the DENV is known to be associated with diverse clinical outcomes, information regarding the genetic composition of circulating virus could be beneficial in designing an effective intervention strategy.