The neglected arboviral infections in mainland China

Trends in temporal and spatial changes of Japanese encephalitis in Chinese mainland, 2004-2019: A population-based surveillance study

BACKGROUND

Japanese encephalitis (JE) is a serious health concern in China, with approximately 80 % of global infections occurring in China. To develop effective prevention and control strategies, this study explored the epidemiological characteristics of JE in China based on spatiotemporal data, to understand the patterns and trends of JE incidence in different regions and time periods.

METHOD

The incidence and mortality rates of JE were extracted from the Public Health Data Center, the official website of the National Health Commission of the People's Republic of China, and the National Notifiable Infectious Disease Surveillance System from 2004 to 2019. Joinpoint regression was applied to examine the spatiotemporal patterns and annual percentage change in incidence and mortality of the JE.

RESULTS

From 2004 to 2019, a total of 43,569 cases of JE were diagnosed, including 2081 deaths. The annual incidence rate of JE decreased from 0.4171/100,000 in 2004 to 0.0298/100,000 in 2019, with an annual percentage change (APC) of -13.5 % (P < 0.001). The annual mortality rate of JE showed three stages of change, with inflection points in 2006 and 2014. The incidence and mortality rates of JE have declined in all provinces of China, and more cases were reported in 0-14 years of age, accounting for nearly 80 % of all patients.

CONCLUSIONS

The morbidity and mortality rates of JE in China are generally on a downward trend, and emphasis should be placed on strengthening disease surveillance in special areas and populations, popularizing vaccination, and increasing publicity.

Transcriptomic Investigation of the Virus Spectrum Carried by Midges in Border Areas of Yunnan Province

Yunnan province in China shares its borders with three neighboring countries: Myanmar, Vietnam, and Laos. The region is characterized by a diverse climate and is known to be a suitable habitat for various arthropods, including midges which are notorious for transmitting diseases which pose significant health burdens affecting both human and animal health. A total of 431,100 midges were collected from 15 different locations in the border region of Yunnan province from 2015 to 2020. These midges were divided into 37 groups according to the collection year and sampling site. These 37 groups of midges were then homogenized to extract nucleic acid. Metatranscriptomics were used to analyze their viromes. Based on the obtained cytochrome C oxidase I gene (COI) sequences, three genera were identified, including one species of Forcipomyia, one species of Dasyhelea, and twenty-five species of Culicoides. We identified a total of 3199 viruses in five orders and 12 families, including 1305 single-stranded positive-stranded RNA viruses (+ssRNA) in two orders and seven families, 175 single-stranded negative-stranded RNA viruses (-ssRNA) in two orders and one family, and 1719 double-stranded RNA viruses in five families. Six arboviruses of economic importance were identified, namely Banna virus (BAV), Japanese encephalitis virus (JEV), Akabane virus (AKV), Bluetongue virus (BTV), Tibetan circovirus (TIBOV), and Epizootic hemorrhagic disease virus (EHDV), all of which are capable, to varying extents, of causing disease in humans and/or animals. The survey sites in this study basically covered the current distribution area of midges in Yunnan province, which helps to predict the geographic expansion of midge species. The complexity and diversity of the viral spectrum carried by midges identified in the study calls for more in-depth research, which can be utilized to monitor arthropod vectors and to predict the emergence and spread of zoonoses and animal epidemics, which is of great significance for the control of vector-borne diseases.

Viromes of Haemaphysalis longicornis reveal different viral abundance and diversity in free and engorged ticks

Haemaphysalis longicornis ticks, commonly found in East Asia, can transmit various pathogenic viruses, including the severe fever with thrombocytopenia syndrome virus (SFTSV) that has caused febrile diseases among humans in Hubei Province. However, understanding of the viromes of H. longicornis was limited, and the prevalence of viruses among H. longicornis ticks in Hubei was not well clarified. This study investigates the viromes of both engorged (fed) and free (unfed) H. longicornis ticks across three mountainous regions in Hubei Province from 2019 to 2020. RNA-sequencing analysis identified viral sequences that were related to 39 reference viruses belonging to unclassified viruses and seven RNA viral families, namely Chuviridae, Nairoviridae, Orthomyxoviridae, Parvoviridae, Phenuiviridae, Rhabdoviridae, and Totiviridae. Viral abundance and diversity in these ticks were analysed, and phylogenetic characteristics of the Henan tick virus (HNTV), Dabieshan tick virus (DBSTV), Okutama tick virus (OKTV), and Jingmen tick virus (JMTV) were elucidated based on their full genomic sequences. Prevalence analysis demonstrated that DBSTV was the most common virus found in individual H. longicornis ticks (12.59%), followed by HNTV (0.35%), whereas JMTV and OKTV were not detected. These results improve our understanding of H. longicornis tick viromes in central China and highlight the role of tick feeding status and geography in shaping the viral community. The findings of new viral strains and their potential impact on public health raise the need to strengthen surveillance efforts for comprehensively assessing their spillover potentials.

Inhibition of tick-borne encephalitis virus in cell cultures by ribavirin

Tick-borne encephalitis virus (TBEV) belonging to arboviruses is a major member of zoonotic pathogens. TBEV infection causes severe human encephalitis without specific antiviral drugs. Due to its use of antiviral drug against a wide range of viruses, we investigated antiviral effect of ribavirin against TBEV in susceptible human cell lines A549 and SH-SY5Y. Ribavirin displayed minor cytotoxicity on multiple cell lines. Ribavirin obviously impaired TBEV replication and protected the infected cells from cytopathic effect. Importantly, ribavirin markedly inhibited TBEV propagation, as evidenced by impairment of TBEV production and viral RNA replication. Treatment with ribavirin (co-treatment and post-treatment) led to a dose-dependent reduction in TBEV titers as well as the viral RNA levels. Antiviral protein myxovirus resistance A mRNA expression was significantly up-regulated and signal transducer and activator of transcription 3 was activated in TBEV-infected A549 cells upon the ribavirin treatment. Induction of inflammatory cytokine tumor necrosis factor alpha by TBEV was decreased in A549 cells with the treatment of ribavirin, whereas interleukin 1 beta release appeared to be unaffected. These results suggest that ribavirin might represent a promising safe and effective antiviral drug against TBEV.

Recent Population Dynamics of Japanese Encephalitis Virus

Japanese encephalitis virus (JEV) causes acute viral encephalitis in humans and reproductive disorders in pigs. JEV emerged during the 1870s in Japan, and since that time, JEV has been transmitted exclusively throughout Asia, according to known reporting and sequencing records. A recent JEV outbreak occurred in Australia, affecting commercial piggeries across different temperate southern Australian states, and causing confirmed infections in humans. A total of 47 human cases and 7 deaths were reported. The recent evolving situation of JEV needs to be reported due to its continuous circulation in endemic regions and spread to non-endemics areas. Here, we reconstructed the phylogeny and population dynamics of JEV using recent JEV isolates for the future perception of disease spread. Phylogenetic analysis shows the most recent common ancestor occurred about 2993 years ago (YA) (95% Highest posterior density (HPD), 2433 to 3569). Our results of the Bayesian skyline plot (BSP) demonstrates that JEV demography lacks fluctuations for the last two decades, but it shows that JEV genetic diversity has increased during the last ten years. This indicates the potential JEV replication in the reservoir host, which is helping it to maintain its genetic diversity and to continue its dispersal into non-endemic areas. The continuous spread in Asia and recent detection from Australia further support these findings. Therefore, an enhanced surveillance system is needed along with precautionary measures such as regular vaccination and mosquito control to avoid future JEV outbreaks.

Persistence of Tembusu Virus in Culex tritaeniorhynchus in Yunnan Province, China

The Tembusu virus (TMUV), a member of the Flaviviridae family, can be transmitted via mosquitoes and cause poultry disease. In 2020, a strain of TMUV (YN2020-20) was isolated from mosquito samples collected in Yunnan province, China. In vitro experiments showed that TMUV-YN2020-20 produced a significant cytopathic effect (CPE) in BHK, DF-1, and VERO cells, while the CPE in C6/36 cells was not significant. Phylogenetic analysis revealed that the strain belonged to Cluster 3.2 and was closely related to the Yunnan mosquito-derived isolates obtained in 2012 and the Shandong avian-derived isolate obtained in 2014. Notably, TMUV-YN2020-20 developed five novel mutations (E-V358I, NS1-Y/F/I113L, NS4A-T/A89V, NS4B-D/E/N/C22S, and NS5-E638G) at loci that were relatively conserved previously. The results of this study demonstrate the continuous circulation and unique evolution of TMUV in mosquitoes in Yunnan province and suggest that appropriate surveillance should be taken.

DNA virome of ticks in the Northeast and Hubei provinces of China reveals diverse single-stranded circular DNA viruses

BACKGROUND

Ticks are medically important vectors capable of transmitting a variety of pathogens to and between host species. Although the spectrum of tick-borne RNA viruses has been frequently investigated, the diversity of tick-borne DNA viruses remains largely unknown.

METHODS

A total of 1571 ticks were collected from forests and infested animals, and the diversity of the viruses they harbored was profiled using a DNA-specific virome method. The viromic data were phylogenetically analyzed and validated by PCR assays.

RESULTS

Although diverse and abundant prokaryotic viruses were identified in the collected ticks, only eukaryotic DNA viruses with single-stranded circular genomes covering the anelloviruses and circular replication-associated (Rep) protein-encoding single-stranded (CRESS) DNA viruses were recovered from ticks. Anelloviruses were detected only in two tick pools, but CRESS DNA viruses were prevalent across these ticks except in one pool of Dermacentor spp. ticks. Phylogenetic analyses revealed that these tick-borne CRESS DNA viruses were related to viruses recovered from animal feces, tissues and even environmental samples, suggesting that their presence may be largely explained by environmental factors rather than by tick species and host blood meals.

CONCLUSIONS

Based on the results, tick-borne eukaryotic DNA viruses appear to be much less common than eukaryotic RNA viruses. Investigations involving a wider collection area and more diverse tick species are required to further support this speculation.

Distribution pattern of Crimean-Congo Hemorrhagic Fever in Asia and the Middle East

Crimean-Congo Hemorrhagic Fever (CCHF) is one of the most important vector-borne diseases of zoonotic potential that can be acquired following the bite of the Hyalomma species of ticks. It is a highly prevalent disease in Asia and the Middle East. The risk factors of this disease are contact with infected tissue, blood, patient, or livestock in the acute viremic phase, infected tick bites, or the manual removal of ticks. The disease is clinically described as progressive hemorrhages, fever, and pain in musculature. Biochemical tests reveal elevated levels of creatinine phosphokinase, alanine transaminase, aspartate aminotransferase, and lactate dehydrogenase. Clotting time is prolonged in pro-thrombin tests, and pathogenesis is mostly related to the disruption of the epithelium during viral replication and indirectly by secreting cytotoxic molecules. These molecules cause endothelial activation and result in the loss of function. Supportive therapy is given through blood or plasma infusions to treat or manage the patients. According to the most advanced studies, CCHF can be treated by Ribavirin, which is an antiviral drug that shows excellent results in preventing the disease. Health-care staff are more prone to infection. The hemorrhagic phase represents a high risk for accidental exposures. This literature review presents a comprehensive overview of the viral epidemiology, zoonotic perspectives, and significant risk factors of CCHF in various Middle East and Asian countries. Furthermore, the pathophysiology and preventive strategies of CCHF have also been discussed as well as legislation and policies regarding public outreach programs, research, and development aimed at infection prevention and control that are required at a global level.

Changing Paradigm in the epidemiology of Japanese encephalitis in India

Japanese encephalitis (JE) is a very serious public health problem in India and the conducive environment permit its emergence in non-endemic areas in the country. There are constant changes taking place in the pattern of current agricultural practices and vector breeding habitats which had far-reaching consequences on the epidemiology of JE and the severity of epidemic outbreaks today. Due to the continuous ecological changes taking place, vectors changed in their breeding dynamics, feeding, and resting behavior and started invading previously non-endemic areas. JE has recently spread to new territories due to land-use changes, including forest fragmentation and concentrated livestock production. Changes in the livestock population decreased the cattle pig ratio which enhanced the Japanese encephalitis virus (JEV) infection. This review brings forth the present widespread changes encountered that grossly impact the risk of infection in many places for the emergence of Japanese encephalitis and to address the implications for its control.

OUP accepted manuscript

Although metagenomic sequencing has revealed high numbers of viruses in mosquitoes sampled globally, our understanding of how their diversity and abundance varies in time and space as well as by host species and gender remains unclear. To address this, we collected 23,109 mosquitoes over the course of 12 months from a bat-dwelling cave and a nearby village in Yunnan province, China. These samples were organized by mosquito species, mosquito gender, and sampling time for meta-transcriptomic sequencing. A total of 162 eukaryotic virus species were identified, of which 101 were novel, including representatives of seventeen RNA virus multi-family supergroups and four species of DNA virus from the families Parvoviridae, Circoviridae, and Nudiviridae. In addition, two known vector-borne viruses—Japanese encephalitis virus and Banna virus—were found. Analyses of the entire virome revealed strikingly different viral compositions and abundance levels in warmer compared to colder months, a strong host structure at the level of mosquito species, and no substantial differences between those viruses harbored by male and female mosquitoes. At the scale of individual viruses, some were found to be ubiquitous throughout the year and across four mosquito species, while most of the other viruses were season and/or host specific. Collectively, this study reveals the diversity, dynamics, and evolution of the mosquito virome at a single location and sheds new lights on the ecology of these important vector animals.

Environmental factors and spatiotemporal distribution of Japanese encephalitis after vaccination campaign in Guizhou Province, China (2004-2016)

Background

Although a vaccination campaign has been conducted since 2004, Japanese encephalitis (JE) is still a public health problem in Guizhou, one of the provinces with the highest incidence of JE in China. The aim of this study was to understand the spatiotemporal distribution of JE and its relationship with environmental factors in Guizhou Province in the post-vaccination era, 2004–2016.

Methods

We collected data on human JE cases in Guizhou Province from 2004 to 2016 from the national infectious disease reporting system. A Poisson regression model was used to analyze the relationship between JE occurrence and environmental factors amongst counties.

Results

Our results showed that the incidence and mortality of JE decreased after the initiation of vaccination. JE cases were mainly concentrated in preschool and school-age children and the number of cases in children over age 15 years was significantly decreased compared with the previous 10 years; the seasonality of JE before and after the use of vaccines was unchanged. JE incidence was positively associated with cultivated land and negatively associated with gross domestic product (GDP) per capita, vegetation coverage, and developed land. In areas with cultivated land coverage < 25%, vegetation coverage > 55%, and urban area coverage > 25%, the JE risk was lower. The highest JE incidence was among mid-level GDP areas and in moderately urbanized areas.

Conclusions

This study assessed the relationship between incidence of JE and environmental factors in Guizhou Province. Our results highlight that the highest risk of JE transmission in the post-vaccination era is in mid-level developed areas.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06857-3.

Phylogenetic analysis of Crimean-Congo hemorrhagic fever virus in inner Mongolia, China

Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne arbovirus that can cause bleeding and death in humans. The mortality rate in humans is between 5 and 30%. The pathogen is prevalent in more than 30 countries in the world. In China, the CCHFV has been reported in Xinjiang province but not in Inner Mongolia province yet. In this report, we phylogenetically analyzed a new CCHFV strain, HANM-18, identified from Hyalomma asiaticum and Hyalomma dromedarii collected in Alxa Left Banner and Alxa Right Banner of Inner Mongolia, China. Complete sequences of CCHFV were obtained by the nested PCR technique and used for phylogenetic analysis of the identity and evolutionary relationship with other CCHFV strains. Our results showed that the S and L fragments of the HANM-18 strain had a high percentage of identity with strains in Xinjiang, China. The M fragment was significantly homologous to South African isolates. In addition, these data also indicate that the HANM-18 strain may have been prevalent in northwestern Inner Mongolia for many years. This discovery will be helpful in CCHF prevention and control in Inner Mongolia, and it also adds new evidence to the epidemiology of CCHF in China.

Crimean-Congo Hemorrhagic Fever Virus in Asia, Africa and Europe

The global spread of ticks and various tick-borne viruses (TBVs) suggests the possibility of new tick-borne diseases emerging. Crimean-Congo hemorrhagic fever virus (CCHFV) is an emerging TBV of the Nairoviridae family that causes serious disease that can be fatal in humans. CCHFV endemic foci can be found in Africa, Asia, the Middle East, and South-Eastern Europe, and has spread to previously unaffected regions and nations, such as Spain, over the last two decades. In this review, we discuss the current situation of CCHFV in Asia, Africa and Europe based on existing knowledge, and we discuss driving factors in the distribution and transmission of the virus, such as the spread of tick vector species and host reservoirs.

Association between meteorological factors and the prevalence dynamics of Japanese encephalitis

Japanese encephalitis (JE) is an acute infectious disease caused by the Japanese encephalitis virus (JEV) and is transmitted by mosquitoes. Meteorological conditions are known to play a pivotal role in the spread of JEV. In this study, a zero-inflated generalised additive model and a long short-term memory model were used to assess the relationship between the meteorological factors and population density of Culex tritaeniorhynchus as well as the incidence of JE and to predict the prevalence dynamics of JE, respectively. The incidence of JE in the previous month, the mean air temperature and the average of relative humidity had positive effects on the outbreak risk and intensity. Meanwhile, the density of all mosquito species in livestock sheds (DMSL) only affected the outbreak risk. Moreover, the region-specific prediction model of JE was developed in Chongqing by used the Long Short-Term Memory Neural Network. Our study contributes to a better understanding of the JE dynamics and helps the local government establish precise prevention and control measures.

The Alphaviral Capsid Protein Inhibits IRAK1-Dependent TLR Signaling

Alphaviruses are arthropod-borne RNA viruses which can cause either mild to severe febrile arthritis which may persist for months, or encephalitis which can lead to death or lifelong cognitive impairments. The non-assembly molecular role(s), functions, and protein–protein interactions of the alphavirus capsid proteins have been largely overlooked. Here we detail the use of a BioID2 biotin ligase system to identify the protein–protein interactions of the Sindbis virus capsid protein. These efforts led to the discovery of a series of novel host–pathogen interactions, including the identification of an interaction between the alphaviral capsid protein and the host IRAK1 protein. Importantly, this capsid–IRAK1 interaction is conserved across multiple alphavirus species, including arthritogenic alphaviruses SINV, Ross River virus, and Chikungunya virus; and encephalitic alphaviruses Eastern Equine Encephalitis virus, and Venezuelan Equine Encephalitis virus. The impact of the capsid–IRAK1 interaction was evaluated using a robust set of cellular model systems, leading to the realization that the alphaviral capsid protein specifically inhibits IRAK1-dependent signaling. This inhibition represents a means by which alphaviruses may evade innate immune detection and activation prior to viral gene expression. Altogether, these data identify novel capsid protein–protein interactions, establish the capsid–IRAK1 interaction as a common alphavirus host–pathogen interface, and delineate the molecular consequences of the capsid–IRAK1 interaction on IRAK1-dependent signaling.

A Metagenomic Analysis of Mosquito Virome Collected From Different Animal Farms at Yunnan-Myanmar Border of China

Metagenomic analysis of mosquito-borne and mosquito-specific viruses is useful to understand the viral diversity and for the surveillance of pathogens of medical and veterinary importance. Yunnan province is located at the southwest of China and has rich abundance of mosquitoes. Arbovirus surveillance is not conducted regularly in this province particularly at animal farms, which have public health as well as veterinary importance. Here, we have analyzed 10 pools of mosquitoes belonging to Culex tritaeniorhyncus, Aedes aegypti, Anopheles sinensis, and Armigeres subalbatus species, collected from different animal farms located at Yunnan province of China by using metagenomic next-generation sequencing technique. The generated viral metagenomic data reveal that the viral community matched by the reads was highly diverse and varied in abundance among animal farms, which contained more than 19 viral taxonomic families, specific to vertebrates, invertebrates, fungi, plants, protozoa, and bacteria. Additionally, a large number of viral reads were related to viruses that are non-classified. The viral reads related to animal viruses included parvoviruses, anelloviruses, circoviruses, flaviviruses, rhabdoviruses, and seadornaviruses, which might be taken by mosquitoes from viremic animal hosts during blood feeding. Notably, the presence of viral reads matched with Japanese encephalitis virus, Getah virus, and porcine parvoviruses in mosquitoes collected from different geographic sites suggested a potential circulation of these viruses in their vertebrate hosts. Overall, this study provides a comprehensive knowledge of diverse viral populations present at animal farms of Yunnan province of China, which might be a potential source of diseases for humans and domestic animals.

Neutralizing antibody rather than cellular immune response is maintained for nearly 20 years among Japanese encephalitis SA14-14-2 vaccinees in an endemic setting

Japanese encephalitis (JE), caused by infection with Japanese encephalitis virus (JEV), is the most important viral encephalitis in Asia. JE incidence has significantly decreased by immunization with live-attenuated vaccine SA14-14-2. However, the duration of immune response overtime after vaccination is inconclusive and may be associated with the risk of JE occurrence in adults. A cross-sectional study was conducted in 961 JE-vaccinated local residents aged 19-20 years in Beijing, China. 620 (65%) and 513 (53%) individuals were anti-JEV IgG antibody and neutralizing antibody (nAb) positive, respectively. The geometric mean titer (GMT) of nAb was 1:11, suggesting a seroprotection among the study population. As for IFN-γ production, peripheral blood mononuclear cell (PBMC) samples isolated from 60 subjects showed negative response following the stimulation with concentrated JEV particles. Overall, longer persistence of nAb response among vaccinees is observed than that of cellular immune response after 17-18 years of vaccination. Taken together, our results not only provide the data for evaluating herd immunity against JEV among vaccinated adults in Beijing but also offer useful information for JE prevention and control in endemic areas.

An outbreak of Japanese encephalitis caused by genotype Ib Japanese encephalitis virus in China, 2018: A laboratory and field investigation

Although Japanese encephalitis virus genotype Ib (JEV GIb) has replaced JEV GIII as the dominant genotype in endemic areas of Asia, no JEV GIb has been isolated from JE cases and natural mosquitoes at the same time in an outbreak of JE. In this study, we conducted virological and molecular biological laboratory tests on JE case samples (serum/cerebrospinal fluid) and locally collected mosquito samples from the 2018 JE outbreak in Ningxia, China. The result of JEV IgM antibody detection showed that 96% (67/70) of the suspected cases were laboratory-confirmed JE cases. Of the mosquitoes collected from local environments, 70% (17400/24900) were Culex tritaeniorhynchus of which 4.6% (16 /348 of the pools tested) were positive for JEV, other mosquitoes were negative. JEVs isolated from both the human cases and C. tritaeniorhynchus specimens belong to JEV GIb and are in the same evolutionary clade according to molecular evolution analyses.

JEV GIb was detected simultaneously from specimens of JE cases and mosquito samples collected in nature in this study, suggesting that the JE outbreak that occurred in Ningxia in 2018 was due to infection of JEV GIb.

Japanese encephalitis virus (JEV) is recognized as an important encephalitis pathogen all over the world. Its genotype is divided into GI-V. In recent years, JEV GIb (a temperate genotype) has gradually replaced GIII as the prevalent strain in JE endemic areas. Although JEV GIb originated from tropical Asia along with JEV GIa, it has rapidly spread for its advantages in wintering and infecting vectors. Although there have been epidemics caused by JEV GI and GIII, there have been no reports of a JE outbreak caused by JEV GIb alone in northeastern Asia. However, a JE outbreak occurred in the Ningxia Hui Autonomous Region in northern China in summer 2018 which was the first outbreak in Ningxia in recent decades. This paper presents a series of laboratory and field studies of this outbreak. The strain isolated from JE cases as well as JEV detected in Culex tritaeniorhynchus collected from local areas in nature all belonged to JEV GIb and were in the same evolutionary clade. This is the first report of a JE outbreak caused by JEV GIb infection in northeastern Asia (latitude 35 ° 14’– 39 ° 23’ N, longitude 104 ° 17’– 107 ° 39’ E), which used to be a low endemic area of JEV GIII.

Epidemiology of tick-borne encephalitis in China, 2007- 2018

Tick-borne encephalitis (TBE) is endemic to Europe and some Asian countries and is prevalent in northeast China. We analyzed the epidemiology of TBE in China from 2007 to 2018. A total of 3,364 TBE cases were reported in mainland China from 2007 to 2018, for an annual incidence of 0.09 to 0.44/100,000. Among the TBE cases, 89.92% were reported in forest areas (41.94% in DaXingAnLing, 8.70% in XiaoXingAnLing, and 39.21% in ChangBaiShan) in northeast China. The TBE cases were primarily male with a proportion of 67.15% (2,259/3,364 cases) and in 40–49-year age group with a proportion of 31.89% (1,073/3,364 cases). The epidemiology of TBE differed slightly among the three forest regions. Domestic workers and forestry workers accounted for the most of the TBE cases in DaXingAnLing, and domestic workers and farmers in XiaoXingAnLing and ChangBaiShan, respectively. The TBE cases mainly occurred from April to August with a peak in June. The TBE laboratory confirmed rate in DaXingAnLing (84.14%, 1,189/1,413 cases) was highest, compared with XiaoXingAnLing and ChangBaiShan (13.99% and 11.37%, respectively). Moreover, the hospital with the highest laboratory confirmed rate (88.01%, 1,336/1,518 cases) was Inner Mongolia Forestry General Hospital of DaXingAnling region. Systematic enhanced TBE surveillance and a vaccination program are needed to improve the laboratory confirmed rate and reduce the incidence of TBE in northeast China.

A viral metagenomic analysis reveals rich viral abundance and diversity in mosquitoes from pig farms

Mosquitoes harbour a diversity of viruses and are responsible for several mosquito-borne viral diseases of humans and animals, thereby leading to major public health concerns, and significant economic losses across the globe. Viral metagenomics offers a great opportunity for bulk analysis of viral genomes retrieved directly from environmental samples. In this study, we performed a viral metagenomic analysis of five pools of mosquitoes belonging to Aedes, Anopheles and Culex species, collected from different pig farms in the vicinity of Shanghai, China, to explore the viral community carried by mosquitoes. The resulting metagenomic data revealed that viral community in the mosquitoes was highly diverse and varied in abundance among pig farms, which comprised of more than 48 viral taxonomic families, specific to vertebrates, invertebrates, plants, fungi, bacteria and protozoa. In addition, a considerable number of viral reads were related to viruses that are not classified by host. The read sequences related to animal viruses included parvoviruses, anelloviruses, circoviruses, flavivirus, rhabdovirus and seadornaviruses, which might be taken up by mosquitoes from viremic animal hosts during blood feeding. Notably, sample G1 contained the most abundant sequence related to Banna virus, which is of public health interest because it causes encephalitis in humans. Furthermore, non-classified viruses also shared considerable virus sequences in all the samples, presumably belonging to unexplored virus category. Overall, the present study provides a comprehensive knowledge of diverse viral populations carried by mosquitoes at pig farms, which is a potential source of diseases for mammals including humans and animals. These viral metagenomic data are valuable for assessment of emerging and re-emerging viral epidemics.

Hypoglycemic Toxins and Enteroviruses as Causes of Outbreaks of Acute Encephalitis-Like Syndrome in Children, Bac Giang Province, Northern Vietnam

We investigated the cause of seasonal outbreaks of pediatric acute encephalitis-like syndrome associated with litchi harvests (May–July) in northern Vietnam since 2008. Nineteen cerebrospinal fluid samples were positive for human enterovirus B, and 8 blood samples were positive for hypoglycemic toxins present in litchi fruits. Patients who were positive for hypoglycemic toxins had shorter median times between disease onset and admission, more reports of seizures, more reports of hypoglycemia (glucose level <3 mmol/L), lower median numbers of leukocytes in cerebrospinal fluid, and higher median serum levels of alanine aminotransferase and aspartate transaminase than did patients who were positive for enteroviruses. We suggest that children with rapidly progressing acute encephalitis-like syndrome at the time of the litchi harvest have intoxication caused by hypoglycemic toxins, rather than viral encephalitis, as previously suspected. These children should be urgently treated for life-threatening hypoglycemia.

Tick-borne encephalitis in Europe: a brief update on epidemiology, diagnosis, prevention, and treatment

Tick-borne encephalitis (TBE) is an emerging health threat that is spreading in many parts of Europe. The mix of socio-economical, ecological and climatic factors as well as the presence of more susceptible hosts is actively contributing to the increasing number of TBE reported cases. TBE is an important cause of central nervous system (CNS) infection that can result in long-term neurological sequelae and even death. Diagnosis of TBE relays mainly on high clinical suspicion confirmed by serological and molecular assays both on serum and cerebrospinal fluid (CSF) with an ancillary role for neuroimaging in supporting the diagnosis. No specific antiviral treatment is currently available for TBE; indeed, supportive treatment as well as intensive care and assisted ventilation in severe forms may be needed. Because of limited option for TBE treatment, of crucial importance is effective vaccination to prevent disease-related morbidity and mortality. Due to expanding proportion of subject possibly exposed to TBE (and new populations such as: unaware travellers to TBE-endemic areas and immunocompromised patients), we performed a comprehensive review of TBE epidemiology, clinical presentation, current available diagnostic tools and treatment.

A Gut Commensal Bacterium Promotes Mosquito Permissiveness to Arboviruses

Mosquitoes are hematophagous vectors that can acquire human viruses in their intestinal tract. Here, we define a mosquito gut commensal bacterium that promotes permissiveness to arboviruses. Antibiotic depletion of gut bacteria impaired arboviral infection of a lab-adapted Aedes aegypti mosquito strain. Reconstitution of individual cultivable gut bacteria in antibiotic-treated mosquitoes identified Serratia marcescens as a commensal bacterium critical for efficient arboviral acquisition. S. marcescens facilitates arboviral infection through a secreted protein named SmEnhancin, which digests membrane-bound mucins on the mosquito gut epithelia, thereby enhancing viral dissemination. Field Aedes mosquitoes positive for S. marcescens were more permissive to dengue virus infection than those free of S. marcescens. Oral introduction of S. marcescens into field mosquitoes that lack this bacterium rendered these mosquitoes highly susceptible to arboviruses. This study defines a commensal-driven mechanism that contributes to vector competence, and extends our understanding of multipartite interactions among hosts, the gut microbiome, and viruses.

Influence of Host and Environmental Factors on the Distribution of the Japanese Encephalitis Vector Culex tritaeniorhynchus in China

Culex tritaeniorhynchus is an important vector that transmits a variety of human and animal diseases. Japanese encephalitis (JE), an endemic disease in the Asia-Pacific region, is primarily transmitted by Cx. tritaeniorhynchus. Insufficient monitoring of vector mosquitoes has led to a poor understanding of the distribution of Cx. tritaeniorhynchus in China. To delineate the habitat of Cx. tritaeniorhynchus and any host and environmental factors that affect its distribution, we used a maximum entropy modeling method to predict its distribution in China. Our models provided high resolution predictions on the potential distribution of Cx. tritaeniorhynchus. The predicted suitable habitats of the JE vector were correlated with areas of high JE incidence in parts of China. Factors driving the distribution of Cx. tritaeniorhynchus in China were also revealed by our models. Furthermore, human population density and the maximum NDVI were the most important predictors in our models. Bioclimate factors and elevation also significantly impacted the distribution of Cx. tritaeniorhynchus. Our findings may serve as a reference for vector and disease control.

Detection of West Nile Virus Infection in Viral Encephalitis Cases, China

This study detected West Nile virus (WNV) infection in serum samples of patients clinically diagnosed with viral encephalitis in the Japanese encephalitis virus (JEV) endemic area (seven provinces) and JEV nonendemic area (Xinjiang province) in China from 2011 to 2012. In JEV endemic areas, there were 22 positive cases of WNV immunoglobulin M (IgM) antibody in serum specimens of 65 JEV patients (JEV IgM antibody positive) in the acute phase, whereas WNV IgM antibodies were not detected in serum specimens of 63 non-JEV patients (JEV IgM antibody negative). However, the titer of JEV-neutralizing antibody was four times higher than that of WNV-neutralizing antibody in WNV-IgM-positive serum specimens. Detection was also conducted in serum specimens collected from 12 patients clinically diagnosed as viral encephalitis in Xinjiang; five serum specimens were WNV IgM antibody positive, and there were fourfold differences in WNV-neutralizing antibody titers between convalescent and acute serum. Meanwhile JEV-neutralizing antibody titer was negative or significantly lower than that of WNV-neutralizing antibody in the same specimens. WNV IgM antibodies positive were detected in acute serum specimens of patients clinically diagnosed with JEV infection in JEV-endemic areas, but no WNV neutralization antibodies were detected fourfold greater than that of the corresponding JEV antibodies. Clinical cases of WNV infection were detected in patients clinically diagnosed with viral encephalitis in Xinjiang.

An Outbreak of Japanese Encephalitis in Adults in Northern China, 2013: A Population-Based Study

BACKGROUND

A Japanese encephalitis (JE) epidemic occurred in 2013 in China. The aim of this study was to determine the spatial-temporal pattern of JE cases in adults occurring in 2013, as well as identify potential hotspots of incidences in the afflicted regions in China.

METHODS/PRINCIPAL FINDINGS

To generate a spatial-temporal pattern of JE cases in China, epidemiological and demographic data between 2011 and 2013 were collected. Our results indicate that the total number of JE cases in 2013 was significantly higher compared with those in 2011 and 2012. While the incidence of JE in individuals aged less than 15 years decreased in 2013, the incidence rate increased substantially in those aged 15 years and older. The population aged over 40 years was associated with the greatest increase of JE. Demographic analysis revealed a consistent increase in the proportion of JE cases aged 15 years and older in 2013 (42%) compared with that in 2012 (15%). In addition, JE cases from areas located between 35°N, 114°E and 40°N, 120°E in northern China were found to account for 27.17% of total JE cases nationwide in 2013, compared with 2.21% and 3.13% in 2011 and 2012, respectively. In these northern regions, the group aged 15 years and older represents the predominant population with JE, accounting for 73% of total cases. Further cluster analysis identified a large number of hotspots of JE in adults (>15 years of age) in northern China.

CONCLUSIONS/SIGNIFICANCE

Unlike the JE epidemics primarily in children below 15 years old in southern China, a significant outbreak of JE occurred in northern China in 2013, with the older age groups being the primary population affected. The increasing incidence of JE in adults has become an important public health issue and poses a new challenge to the successful prevention and control of JE in China, as well as other countries in East Asia.

Complete Genomic Characterization of Three Tick-Borne Encephalitis Viruses Detected Along the China-North Korea Border, 2011

Tick-borne encephalitis virus (TBEV) causes neurological infections with serious sequelae in Europe and Northeast Asia. In China, the major epidemic areas are along the borders with Russia and North Korea. Although several TBEV isolates have been reported, the biological characteristics of the Chinese strains, especially those along the China-North Korea border, are unclear. In this study, we detected seven TBEV fragment sequences in 602 adult Dermacentor silvarum collected in the Changbai Mountain area of Jilin Province on the China-North Korea border and characterized the genome of three TBEV strains (JLCB11-08, JLCB11-35, and JLCB11-40). These three TBEV strains belong to the TBEV-Far Eastern (TBEV-FE) genotype and clustered most closely with the Svetlogorie and Kavalerovo strains from Russia. In addition, the TBEV strains from Northeast China clustered geographically within the TBEV-FE subtype branch. These findings will facilitate further research on the distinct genetic groupings of TBEV strains in China.

How Socio-Environmental Factors Are Associated with Japanese Encephalitis in Shaanxi, China-A Bayesian Spatial Analysis

Evidence indicated that socio-environmental factors were associated with occurrence of Japanese encephalitis (JE). This study explored the association of climate and socioeconomic factors with JE (2006–2014) in Shaanxi, China. JE data at the county level in Shaanxi were supplied by Shaanxi Center for Disease Control and Prevention. Population and socioeconomic data were obtained from the China Population Census in 2010 and statistical yearbooks. Meteorological data were acquired from the China Meteorological Administration. A Bayesian conditional autoregressive model was used to examine the association of meteorological and socioeconomic factors with JE. A total of 1197 JE cases were included in this study. Urbanization rate was inversely associated with JE incidence during the whole study period. Meteorological variables were significantly associated with JE incidence between 2012 and 2014. The excessive precipitation at lag of 1–2 months in the north of Shaanxi in June 2013 had an impact on the increase of local JE incidence. The spatial residual variations indicated that the whole study area had more stable risk (0.80–1.19 across all the counties) between 2012 and 2014 than earlier years. Public health interventions need to be implemented to reduce JE incidence, especially in rural areas and after extreme weather.

Mosquito-Associated Viruses in China

Mosquitoes are classified into approximately 3500 species and further grouped into 41 genera. Epidemiologically, they are considered to be among the most important disease vectors in the world and they can harbor a wide variety of viruses. Several mosquito viruses are considered to be of significant medical importance and can cause serious public health issues throughout the world. Such viruses are Japanese encephalitis virus (JEV), dengue virus (DENV), chikungunya virus (CHIKV), and Zika virus (ZIKV). Others are the newly recognized mosquito viruses such as Banna virus (BAV) and Yunnan orbivirus (YNOV) with unclear medical significance. The remaining mosquito viruses are those that naturally infect mosquitoes but do not appear to infect humans or other vertebrates. With the continuous development and improvement of mosquito and mosquito-associated virus surveillance systems in China, many novel mosquito-associated viruses have been discovered in recent years. This review aims to systematically outline the history, characteristics, distribution, and/or current epidemic status of mosquito-associated viruses in China.

Tick-Borne Viruses

Ticks are important vectors for the transmission of pathogens including viruses. The viruses carried by ticks also known as tick-borne viruses (TBVs), contain a large group of viruses with diverse genetic properties and are concluded in two orders, nine families, and at least 12 genera. Some members of the TBVs are notorious agents causing severe diseases with high mortality rates in humans and livestock, while some others may pose risks to public health that are still unclear to us. Herein, we review the current knowledge of TBVs with emphases on the history of virus isolation and identification, tick vectors, and potential pathogenicity to humans and animals, including assigned species as well as the recently discovered and unassigned species. All these will promote our understanding of the diversity of TBVs, and will facilitate the further investigation of TBVs in association with both ticks and vertebrate hosts.

Molecular epidemiology of dengue viruses in three provinces of Lao PDR, 2006-2010

Few data on dengue epidemiology are available for Lao PDR. Here, we provide information on the complexity of dengue epidemiology in the country, demonstrating dynamic circulation that varies over space and time, according to serotype. We recruited 1,912 consenting patients presenting with WHO dengue criteria at Mahosot Hospital, Vientiane (central Laos), between 2006 and 2010. Between 2008 and 2010, 1,413 patients with undifferentiated fever were also recruited at Luang Namtha (LNT) Provincial Hospital (northern Laos) and 555 at Salavan (SV) Provincial Hospital (southern Laos). We report significant variations in Dengue virus (DENV) circulation between the three sites. Peaks of DENV infection were observed in the rainy seasons, although 11% of confirmed cases in the provinces and 4.6% in the capital were detected during the dry and cool seasons (between December and February). Four DENV serotypes were detected among the 867 RT-PCR positive patients: 76.9% DENV-1, 9.6% DENV-2, 7.7% DENV-4 and 5.3% DENV-3. DENV-1 was the predominant serotype throughout the study except in LNT in 2008 and 2009 when it was DENV-2. Before July 2009, DENV-2 was not detected in SV and only rarely detected in Vientiane. DENV-3 and DENV-4 were commonly detected in Vientiane, before 2008 for DENV-4 and after 2009 for DENV-3. The phylogenetic analyses of DENV envelope sequences suggest concurrent multiple introductions of new strains as well as active DENV circulation throughout Laos and with neighboring countries. It is therefore of great importance to develop and strengthen a year-round nation-wide surveillance network in order to collect data that would allow anticipation of public health issues caused by the occurrence of large dengue outbreaks.

Dengue is a mosquito-borne disease that can be caused by 4 viruses. It is a flu-like disease but can sometime be more severe and cause hemorrhage or death. An estimated 390 million people are infected every year, mainly in the Western Pacific and in South-East Asia. In Laos, where our study was conducted from 2006 to 2010, little was known on the circulation of the different dengue viruses. A total of 1,912 patients were recruited at Mahosot Hospital, Vientiane (central Laos), 1,413 patients at Luang Namtha Provincial Hospital (northern Laos) and 555 at Salavan Provincial Hospital (southern Laos). Although most Dengue virus infections were detected during rainy seasons (where mosquitoes are the most active) in all three provinces, some patients were also infected during the dryer months. All 4 dengue viruses were detected with different distributions: mostly type 1 in the capital and in the South, and type 1 and 2 in equal proportion in the north. Type 3 and 4 were not detected in Luang Namtha and rarely in Salavan. Comparison of Dengue virus sequences from Laos with sequences collected worldwide showed an active year-round circulation of dengue within Laos and with neighboring countries. It is hence of great importance to develop and strengthen a year-round nation-wide surveillance network in order to collect data that would allow anticipation of public health issues caused by the occurrence of large dengue outbreaks.

Arboviruses and their related infections in China: A comprehensive field and laboratory investigation over the last 3 decades

Since the 1980s, a comprehensive field and laboratory investigation has been conducted throughout China, and a total of 29 virus species belonging to 7 families and 13 genera were identified through virological, morphological, and immunological methods, as well as whole-genome sequencing and molecular genetic analyses. Most of the virus isolates belong to 9 genera in the families Flaviviridae, Bunyaviridae, Togaviridae, and Reoviridae. Among them, 4 genera (Orthobunyavirus, Bunyavirus, Phlebovirus, and Nairovirus) belong to the family Bunyaviridae and 3 genera (Seadonavirus, Orbivirus, and Cypovirus) belong to the family Reoviridae. Analyses of the relationships between viruses and human/animal diseases indicated that Japanese encephalitis virus, dengue virus, severe fever with thrombocytopenia syndrome virus, tick-borne encephalitis virus, Crimean-Congo hemorrhagic fever virus, West Nile virus, and Tahyna virus can cause human and animal infections and disease epidemics in China. This review systematically introduces the current status of the diversity and geographical distribution of arboviruses and vectors in China. In addition, our results provide strong technical support for the prevention and control of arboviral diseases, the treatment of epidemics, and the early warning and prediction of diseases, and so they are significant for the control and prevention of arboviral diseases in Asia and around the world.

Investigation on Mosquito-Borne Viruses at Lancang River and Nu River Watersheds in Southwestern China

During 2007 and 2010, an extensive entomological survey was performed to assess the distribution of mosquitoes and mosquito-borne arboviruses at Lancang River and Nu River watersheds in southwestern China. A total of 20,450 mosquitoes consisting 20 species was trapped and submitted 261 pools according to species and location. Culex tritaeniorhynchus and Anopheles sinensis were the most abundant species. Eighty-seven isolates representing 11 virus species in 8 genera were obtained from 6 mosquito species. The new isolates were identified as Getah virus (GETV), Japanese encephalitis virus (JEV), Yunnan Culex-related flavivirus (YNCxFV), Yunnan Aedes-related flavivirus (YNAeFV), Banna virus (BAV), Yunnan orbivirus (YUOV), Banna orbivirus (BAOV), Yunnan totivirus (YNToV), Nam Dinh virus (NDiV), Menghai rhabdovirus (MRV), and Anopheles minimus iridovirus (AMIV). These viruses included confirmed or potential pathogen of human disease, such as JEV, BAV, and NDiV, and several novel or reassortant arboviruses, such as YNAeFV, MRV, AMIV, and BAOV. GETV, JEV, YNCxFV, and NDiV were widely prevalent in the whole basin of the two rivers. The findings contribute to our understanding of the diversity and wide distribution of mosquito-borne arboviruses in the area, and are helpful to explore pathogenic evidence for fevers and viral encephalitis of unknown etiology.

ZIKA virus isolated from mosquitoes: a field and laboratory investigation in China, 2016

A field investigation of arboviruses was conducted in Dejiang, Guizhou Province in the summer of 2016. A total of 8,795 mosquitoes, belonging to four species of three genera, and 1,300 midges were collected. The mosquito samples were identified on site according to their morphology, and the pooled samples were ground and centrifuged in the laboratory. The supernatant was incubated with mosquito tissue culture cells (C6/36) and mammalian cells (BHK-21) for virus isolation. The results indicated that 40% (3,540/8,795) were Anopheles sinensis, 30% (2,700/8,795) were Culex pipiens quinquefasciatus, and 29% (2,530/8,795) were Armigeres subbalbeatus. Furthermore, a total of eight virus isolates were obtained, and genome sequencing revealed two Zika viruses (ZIKVs) isolated from Culex pipiens quinquefasciatus and Armigeres subbalbeatus, respectively; three Japanese encephalitis viruses (JEVs) isolated from Culex pipiens quinquefasciatus; two Banna viruses (BAVs) isolated from Culex pipiens quinquefasciatus and Anopheles sinensis, respectively; and one densovirus (DNV) isolated from Culex pipiens quinquefasciatus. The ZIKVs isolated from the Culex pipiens quinquefasciatus and Armigeres subbalbeatus mosquitoes represent the first ZIKV isolates in mainland China. This discovery presents new challenges for the prevention and control of ZIKV in China, and prompts international cooperation on this global issue.

Etiology and prognosis of acute viral encephalitis and meningitis in Chinese children: a multicentre prospective study

BACKGROUND

In China, there were few studies about the pathogens of acute viral encephalitis and meningitis in children in recent years. The aims of this study were to characterize the etiology and prognosis of acute viral encephalitis and meningitis in Chinese children.

METHODS

This was a multicentre prospective study. Two hundred and sixty one viral encephalitis patients and 285 viral meningitis patients were enrolled. The mean age of viral encephalitis and meningitis were 5.88 ± 3.60 years and 6.39 ± 3.57 years, respectively. Real-time reverse transcription PCR and multiplex PCR were used to detect human enteroviruses and herpes viruses in cerebrospinal fluid (CSF) of patients with encephalitis or meningitis. The enzyme-linked immune absorbent assay (ELISA) was used for detecting IgM antibody against Japanese encephalitis virus (JEV) in CSF and against mumps virus, tick-borne encephalitis virus (TBEV), dengue virus and rubella virus in acute serum. The clinical and outcome data were collected during patients' hospitalization.

RESULTS

The etiology of viral encephalitis was confirmed in 52.5% patients. The primary pathogen was human enteroviruses (27.7%) in viral encephalitis. The incidence of sequelae and the fatality rate of viral encephalitis with confirmed etiology were 7.5% and 0.8%, respectively. The etiology of viral meningitis was identified in 42.8% cases. The leading pathogen was also human enteroviruses (37.7%) in viral meningitis. The prognosis of viral meningitis was favorable with only 0.7% patients had neurological sequelae.

CONCLUSIONS

Human enteroviruses were the leading cause both in acute viral encephalitis and viral meningitis in children. The incidence of sequelae and fatality rate of viral encephalitis with confirmed etiology were 7.5% and 0.8%, respectively. The prognosis of viral meningitis was favorable compared to viral encephalitis.

Pigsties near dwellings as a potential risk factor for the prevalence of Japanese encephalitis virus in adult in Shanxi, China

Background

The increasing trend of adult cases of Japanese encephalitis (JE) in China, particularly in northern China, has become an important public health issue. We conducted an epidemiological investigation in the south of Shanxi Province to examine the relationships between mosquitoes, Japanese encephalitis virus (JEV), and adult JE cases.

Methods

Mosquito specimens were collected from the courtyards of farmers’ households and pig farms in Shanxi Province. Mosquitoes were pooled, homogenized, and centrifuged. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect mosquito-borne arbovirus genes in homogenates. Specimens positive for these genes were inoculated into the baby hamster kidney cell line (BHK-21) to isolate virus. Minimum infection rate was calculated and phylogenetic analyses were performed.

Results

A total of 7 943 mosquitoes belonging to six species in four genera were collected; Culex tritaeniorhynchus accounted for 73.08% (5 805/7 943), C. pipiens pallens for 24.75% (1 966/7 943), and the remaining 3% (104/ 7943) consisted of Anopheles sinensis, Aedes vexans, Ae. dorsalis, and Armigeres subalbatus. Sixteen pools were positive for JEV based on RT-PCR using JEV pre-membrane gene nested primers. Phylogenetic analyses showed that all JEVs belonged to genotype I; two pools were positive using Getah Virus (GETV) gene primers. In addition, one JEV strain (SXYC1523) was isolated from C. pipiens pallens specimens. These results indicate that the minimum infection rate of JEV in mosquito specimens collected from the courtyards of farmers’ households with pigsties was 7.39/1 000; the rate for pig farms was 2.68/1 000; and the rate for farmers’ courtyards without pigsties was zero.

Conclusions

The high-prevalence regions of adult JE investigated in this study are still the natural epidemic focus of JEV. Having pigsties near dwellings is a potential risk factor contributing to the prevalence of adult JE. To prevent the occurrence of local adult JE cases, a recommendation was raised that, besides continuing to implement the Expanded Program on Immunization for children, the government should urge local farmers to cease raising pigs in their own courtyards to reduce the probability of infection with JEV.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-017-0312-4) contains supplementary material, which is available to authorized users.

PCR denaturing gradient gel electrophoresis as a useful method to identify of intestinal bacteria flora in Haemaphysalis flava ticks

Ticks are blood-sucking ectoparasites of great medical and veterinary significance that can transmit bacteria, protozoa, fungi and viruses, causing a variety of human and animal diseases worldwide. In the present study, the intestinal bacterial flora associated with Haemaphysalis flava ticks in different developmental stages were analyzed using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE). Eleven distinct DGGE bands were found using PCR-DGGE method. Sequences analyses indicated that they belonged to Bacillus cereus, Candidatus rickettsia, Erwinia sp., Klebsiella pneumoniae, Pectobacterium carotovorum, Pseudomonas aeruginosa, Rickettsia peacockii, Rickettsia helvetica, Rickettsia slovaca, Staphylococcus simulans and Uncultured bacterium clone. Our find that the K. pneumoniae and P. aeruginosa isolates were presented in all H. flava ticks in different developmental stages. The present results indicated that zoonotic pathogens are present in H. flava ticks in Henan province, China. To our knowledge, this is the first report on intestinal bacterial flora associated with H. flava ticks in China.

Japanese Encephalitis Virus Infection Rate and Detection of Genotype I From Culex tritaeniorhynchus Collected From Jiangsu, China

Information regarding the infection rate and genotype shifts for Japanese encephalitis virus (JEV) are important for JE vaccine application. In Jiangsu province, China, which is one of the provinces with a high prevalence of JE, JEV infection in swine and mosquitoes in certain cities has only been investigated in 2008-2009. Lianyungang City has one of the highest numbers of JE cases in Jiangsu province, and it has a high risk of JEV invasion via migrant birds. JEV infection in vectors in Lianyungang City, which has urban and rural parts, has not been investigated. In 2015-2016, we collected mosquitoes in cowsheds with ultraviolet light traps and detected JEV by reverse transcription-polymerase chain reaction (RT-PCR) method in Culex tritaeniorhynchus in Xintan village, Xuzhuang village, and Xiaogaozhuang village in Lianyungang City, China. The proportion of positive pools, which is calculated by the number of infected pools to the total number of pools tested in these villages, were 16.67%, 20.00%, and 4.17%, respectively, and the minimum infection rates, which is calculated as the ratio of the number of positive pools to the total number of mosquitoes tested, were 3.33‰, 4.00‰, and 0.83‰, respectively. Four JEV strains from positive samples were coded as LYG-1, LYG-2, LYG-3, and LYG-4, and the complete E genes were sequenced. Furthermore, the complete genome of LYG-3 was sequenced. The phylogenetic analysis indicated that all the four JEV strains belonged to genotype I-b. This is the first report of genotype I JEV strain in Jiangsu province. The high JEV infection rate in Culex tritaeniorhynchus indicated a high risk of JE reemergence in Lianyungang. The detected JEV strains may have similar antigenicity to that of SA14-14-2 according to molecular characters. These findings suggest that the vaccine can still be effective in Lianyungang.

Comparing national infectious disease surveillance systems: China and the Netherlands

BACKGROUND

Risk assessment and early warning (RAEW) are essential components of any infectious disease surveillance system. In light of the International Health Regulations (IHR)(2005), this study compares the organisation of RAEW in China and the Netherlands. The respective approaches towards surveillance of arboviral disease and unexplained pneumonia were analysed to gain a better understanding of the RAEW mode of operation. This study may be used to explore options for further strengthening of global collaboration and timely detection and surveillance of infectious disease outbreaks.

METHODS

A qualitative study design was used, combining data retrieved from the literature and from semi-structured interviews with Chinese (5 national-level and 6 provincial-level) and Dutch (5 national-level) experts.

RESULTS

The results show that some differences exist such as in the use of automated electronic components of the early warning system in China ('CIDARS'), compared to a more limited automated component in the Netherlands ('barometer'). Moreover, RAEW units in the Netherlands focus exclusively on infectious diseases, while China has a broader 'all hazard' approach (including for example chemical incidents). In the Netherlands, veterinary specialists take part at the RAEW meetings, to enable a structured exchange/assessment of zoonotic signals.

CONCLUSION

Despite these differences, the main conclusion is that for the two infections studied, the early warning system in China and the Netherlands are remarkably similar considering their large differences in infectious disease history, population size and geographical setting. Our main recommendations are continued emphasis on international corporation that requires insight into national infectious disease surveillance systems, the usage of a One Health approach in infectious disease surveillance, and further exploration/strengthening of a combined syndromic and laboratory surveillance system.

DNA Microarray Platform for Detection and Surveillance of Viruses Transmitted by Small Mammals and Arthropods

Viruses transmitted by small mammals and arthropods serve as global threats to humans. Most emergent and re-emergent viral agents are transmitted by these groups; therefore, the development of high-throughput screening methods for the detection and surveillance of such viruses is of great interest. In this study, we describe a DNA microarray platform that can be used for screening all viruses transmitted by small mammals and arthropods (SMAvirusChip) with nucleotide sequences that have been deposited in the GenBank. SMAvirusChip was designed with more than 15,000 oligonucleotide probes (60-mers), including viral and control probes. Two SMAvirusChip versions were designed: SMAvirusChip v1 contains 4209 viral probes for the detection of 409 viruses, while SMAvirusChip v2 contains 4943 probes for the detection of 416 viruses. SMAvirusChip was evaluated with 20 laboratory reference-strain viruses. These viruses could be specifically detected when alone in a sample or when artificially mixed within a single sample. The sensitivity of SMAvirusChip was evaluated using 10-fold serial dilutions of dengue virus (DENV). The results showed a detection limit as low as 2.6E3 RNA copies/mL. Additionally, the sensitivity was one log10 lower (2.6E2 RNA copies/mL) than quantitative real-time RT-PCR and sufficient to detect viral genomes in clinical samples. The detection of DENV in serum samples of DENV-infected patients (n = 6) and in a whole blood sample spiked with DENV confirmed the applicability of SMAvirusChip for the detection of viruses in clinical samples. In addition, in a pool of mosquito samples spiked with DENV, the virus was also detectable. SMAvirusChip was able to specifically detect viruses in cell cultures, serum samples, total blood samples and a pool of mosquitoes, confirming that cellular RNA/DNA did not interfere with the assay. Therefore, SMAvirusChip may represent an innovative surveillance method for the rapid identification of viruses transmitted by small mammals and arthropods.

The Spatio-temporal Distribution of Japanese Encephalitis Cases in Different Age Groups in Mainland China, 2004 - 2014

BACKGROUND

Japanese encephalitis (JE) is very prevalent in China, but the incidence of JE among children has been greatly reduced by extensive promotion of vaccinations. The incidence of JE among adults, however, has increased in some parts of China.

METHODS/PRINCIPAL FINDINGS

Data on JE in mainland China, in terms of incidence, gender, and age, were collected between 2004 and 2014. We conducted spatial and temporal analyses on data from different age groups. Generally, children aged 0-15 years still represent the major population of JE cases in China, despite the gradual decrease in incidence over years. However, the incidence of JE among adults in several provinces is notably higher than the national average, especially during the epidemic waves in 2006, 2009, and 2013. The JE cases in the 0-15-year-old group are distributed mainly in the area south of the Yangtze River, with peak incidence occurring from July to September. In the adult group, especially for those over 40 years old, the JE cases are concentrated mainly in the area north of the Yangtze River. JE incidence in the adult group in September and October is significantly greater compared to the other groups. Further analysis using Local Indicators of Spatial Association (LISA) reveals that the distribution of adult JE cases in the six provinces north of the Yangtze River, between north 30-35° latitude and east 110-130° longitude, is a hotspot for adult JE cases.

CONCLUSIONS/SIGNIFICANCE

The rate of JE case increase for adults is much greater than for children and has become a public health issue. Therefore, studies on the necessity and feasibility of vaccinating adults who live in JE-endemic areas, but have never been vaccinated for JE, should become a new focus of JE prevention in the future.

Epidemiological trends and characteristics of Japanese encephalitis changed based on the vaccination program between 1960 and 2013 in Guangxi Zhuang Autonomous Region, southern China

Japanese encephalitis (JE) is one of the most severe kinds of viral encephalitis and is prevalent in Asia and the Western Pacific. In China, JE was first reported in the 1940s and became the main cause of viral encephalitis, including in the Guangxi Zhuang Autonomous Region. In 1951, JE was included in the Chinese mandatory disease reporting system. In the pre-vaccine era of the 1960s and 1970s, the incidence of JE continued to rise without any vaccine supply. Since JE vaccines became available in the late 1970s (MBD) and 1989 (LAV-SA-14-14-2), and as JE vaccine became freely available to patients beginning in 2008, the incidence of JE has declined significantly. Despite these gains, outbreaks continue to occur among children in rural and suburban areas. Strengthening vaccine delivery models and improving swine vaccine production are important in order to sustain continuous declines in the incidence of JE in Guangxi.

Isolation and characterization of a Far-Eastern strain of tick-borne encephalitis virus in China

Tick-borne encephalitis virus (TBEV) is a leading cause of human neurological infection in many parts of Europe and Asia. Although several TBEV isolates have been reported, current understanding of the biological characteristics of a Chinese strain is limited. In this study, a Far-Eastern strain of TBEV designated WH2012 was isolated in northern China. Its genome has been sequenced and found to be closely related to other Chinese TBEV isolates. Human cell lines of neural origin exposed to WH2012 showed cytopathic effects and WH2012 replicated most efficiently in human neuroblastoma cells SK-N-SH. In addition, WH2012 possessed a pathogenic potential in the mouse model, characterized by inducing a complete paralysis in the hindlimbs with a fatal outcome. We herein describe the first data regarding biological properties of TBEV from China. This study may help future research on pathogenic mechanisms of the neurological disease induced by TBEV infection in China.

Immunogenicity against Far Eastern and Siberian subtypes of tick-borne encephalitis (TBE) virus elicited by the currently available vaccines based on the European subtype: systematic review and meta-analysis

Tick-borne encephalitis (TBE) virus, which is usually divided into European, Far Eastern and Siberian subtypes, is a serious public health problem in several European and Asian countries. Vaccination is the most effective measure to prevent TBE; cross-subtype protection elicited by the TBE vaccines is biologically plausible since all TBE virus subtypes are closely related. This manuscript systematically explores available data on the cross-subtype immunogenicity elicited by the currently available Western vaccines based on the European subtype. Completed immunization course of 3 doses of both Western vaccines determined very high seroconversion/seropositivity rates against both Far Eastern and Siberian subtypes among previously flavivirus-naïve subjects. All but one study found no statistically significant difference in titers of neutralizing antibodies against strains belonging to homologous and heterologous subtypes. Pooled analysis of randomized controlled trials on head-to-head comparison of immunogenicity of Western and Russian TBE vaccines did not reveal differences in seroconversion rates against Far Eastern isolates in either hemagglutination inhibition (risk ratio = 0.98, p = 0.83) or enzyme-linked immunosorbent (risk ratio = 0.95, p = 0.44) assays after 2 vaccine doses. This suggests that, in regions where a heterogeneous TBE virus population circulates, vaccines based on the European subtype may be used alongside vaccines based on the Far Eastern subtype. Studies on the field effectiveness of TBE vaccines and investigation of vaccination failures, especially in countries where different subtypes co-circulate, will further elucidate TBE vaccination-induced cross-subtype protection.

How environmental conditions impact mosquito ecology and Japanese encephalitis: an eco-epidemiological approach

Japanese encephalitis (JE) is one of the major vector-borne diseases in Southeast Asia and the Western Pacific region, posing a threat to human health. In rural and suburban areas, traditional rice farming and intensive pig breeding provide an ideal environment for both mosquito development and the transmission of JEV among human beings. Combining surveillance data for mosquito vectors, human JE cases, and environmental conditions in Changsha, China, 2004-2009, generalized threshold models were constructed to project the mosquito and JE dynamics. Temperature and rainfall were found to be closely associated with mosquito density at 1, and 4month lag, respectively. The two thresholds, maximum temperature of 22-23°C for mosquito development and minimum temperature of 25-26°C for JEV transmission, play key roles in the ecology of JEV. The model predicts that, in the upper regime, a 1g/m(3) increase in absolute humidity would on average increase human cases by 68-84%. A shift in mosquito species composition in 2007 was observed, and possibly caused by a drought. Effective predictive models could be used in risk management to provide early warnings for potential JE transmission.