Emerging souvenirs—clinical presentation of the returning traveller with imported arbovirus infections in Europe

BackgroundArboviruses are an emerging group of viruses that are causing increasing health concerns globally, including in Europe. Clinical presentation usually consists of a nonspecific febrile illness that may be accompanied by rash, arthralgia and arthritis, with or without neurological or haemorrhagic syndromes. The range of differential diagnoses of other infectious and noninfectious aetiologies is broad, presenting a challenge for physicians. While knowledge of the geographical distribution of pathogens and the current epidemiological situation, incubation periods, exposure risk factors and vaccination history can help guide the diagnostic approach, the nonspecific and variable clinical presentation can delay final diagnosis.Aims and sourcesThis narrative review aims to summarize the main clinical and laboratory-based findings of the three most common imported arboviruses in Europe. Evidence is extracted from published literature and clinical expertise of European arbovirus experts.ContentWe present three cases that highlight similarities and differences between some of the most common travel-related arboviruses imported to Europe. These include a patient with chikungunya virus infection presenting in Greece, a case of dengue fever in Turkey and a travel-related case of Zika virus infection in Romania.ImplicationsEarly diagnosis of travel-imported cases is important to reduce the risk of localized outbreaks of tropical arboviruses such as dengue and chikungunya and the risk of local transmission from body fluids or vertical transmission. Given the global relevance of arboviruses and the continuous risk of (re)emerging arbovirus events, clinicians should be aware of the clinical syndromes of arbovirus fevers and the potential pitfalls in diagnosis.     

Preparing clinicians for (re-)emerging arbovirus infectious diseases in Europe

BackgroundArthropod-borne virus (Arbovirus) infections are considered an emerging threat for Europe, with an increase in cases in recent decades. The increase in global travel and trade has contributed to the introduction of vectors and viruses into new geographical areas. Tropical arboviruses such as dengue and chikungunya have re-emerged causing local, sporadic outbreaks ignited by travel-imported cases. The recent Zika virus outbreak in the Americas highlighted a need to strengthen preparedness for (re-)emerging arbovirus infections globally.AimsTo strengthen preparedness for the early identification of (re-)emerging arbovirus outbreaks in Europe and highlight areas for research.SourcesAn evidence review of published and grey literature together with consultations with European arbovirus experts.ContentThis paper presents an overview of endemic and travel-imported arboviruses of clinical significance in Europe. The overview includes syndromic presentation, risk factors for infection and risk of transmission as well as an update on treatments and vaccinations and surveillance notifications and reporting. The paper also presents predictive modelled risks of further geographical expansion of vectors and viruses.ImplicationsThere are a range of arboviruses of clinical significance to Europe. There has been an increase in notifications of endemic and travel-imported arbovirus cases in recent years and an increased geographical range of vectors and viruses. The heterogeneity in surveillance reporting indicates a risk for the early identification of (re-)emerging outbreaks. The data presented show a need to strengthen preparedness for (re-)emerging arbovirus infections and a need for research into neglected arboviruses, risks of non-vector transmission and effective therapeutics and vaccinations.     

Biological transmission of arboviruses: reexamination of and new insights into components, mechanisms, and unique traits as well as their evolutionary trends

Among animal viruses, arboviruses are unique in that they depend on arthropod vectors for transmission. Field research and laboratory investigations related to the three components of this unique mode of transmission, virus, vector, and vertebrate host, have produced an enormous amount of valuable information that may be found in numerous publications. However, despite many reviews on specific viruses, diseases, or interests, a systematic approach to organizing the available information on all facets of biological transmission and then to interpret it in the context of the evolutionary process has not been attempted before. Such an attempt in this review clearly demonstrates tremendous progress made worldwide to characterize the viruses, to comprehend disease transmission and pathogenesis, and to understand the biology of vectors and their role in transmission. The rapid progress in molecular biologic techniques also helped resolve many virologic puzzles and yielded highly valuable data hitherto unavailable, such as characterization of virus receptors, the genetic basis of vertebrate resistance to viral infection, and phylogenetic evidence of the history of host range shifts in arboviruses. However, glaring gaps in knowledge of many critical subjects, such as the mechanism of viral persistence and the existence of vertebrate reservoirs, are still evident. Furthermore, with the accumulated data, new questions were raised, such as evolutionary directions of virus virulence and of host range. Although many fundamental questions on the evolution of this unique mode of transmission remained unresolved in the absence of a fossil record, available observations for arboviruses and the information derived from studies in other fields of the biological sciences suggested convergent evolution as a plausible process. Overall, discussion of the diverse range of theories proposed and observations made by many investigators was found to be highly valuable for sorting out the possible mechanism(s) of the emergence of arboviral diseases.     

Use of hyperimmune mouse ascitic fluids for arbovirus differentiation by indirect immunofluorescence and conventional serology

The cross-reactivity of 22 arbovirus species (alphaviruses; tick- and mosquito-borne flaviviruses; and selected bunyaviruses) was tested with monovalent immune mouse ascitic fluids by indirect immunofluorescence (IIF) in comparison with classical serological reactions (virus neutralization -- VN; haemagglutination inhibition -- HI; and complement fixation -- CF -- reactions). Known relationships within the virus groups studied were confirmed. As to the differentiation limits, the VN test was followed by IIF. Evaluation of the ratio of heterologous to homologous antibody activities showed that with the exception of antigenically closely related arboviruses (Western equine encephalomyelitis -- Sindbis; Japanese encephalitis -- Murray Valley encephalitis; dengue viruses; California -- Tahyna), most arboviruses within the antigenic complexes tested could be relatively reliably differentiated by IIF.     

Transmission of arboviruses without involvement of arthropod vectors.

Transmission of arboviruses (arthropod-borne viruses belonging to various virus families) without involvement of arthropod vectors has been documented for years, but the reports have not been reviewed systematically. The recent report of West Nile (WN) virus isolation from a hawk in mid-winter in New York (Garmendia et al., J. Clin. Microbiol. 38, 3110-3111, 2000) generated a considerable interest in this mode of arbovirus transmission. In this article, the data available worldwide are analyzed according to the factors involved in such a transmission under natural conditions, mode of infection, virus entry mechanism, administration and efficacy evaluation of vaccines, and significance in agricultural trade and public health. Analysis of numerous reports compiled for this review revealed that peroral and intranasal/aerosol transmissions are very common among arboviruses. The mechanism of virus infections in animals was most extensively studied for intranasal/aerosol infection, confirming two routes of virus spread to central nervous system (CNS), olfactory and hematogenous. To rule out the possibility of asymptomatic, cryptic infection the efficacy evaluation of candidates for vaccines against neurotropic arboviruses should include virus isolation from tissues of not only symptomatic but also of asymptomatic animals that survive intranasal virus challenge. Human activities, such as feeding livestock animals with food containing virus-contaminated meat and assembling a large number of livestock from many geographically-separated locations, have been identified as a cause of spread of some arboviral diseases. Despite numerous laboratory reports, the significance of this mode of transmission of arboviruses under natural conditions was rarely investigated, except for a few viruses important for veterinary medicine.     

Persistence of arboviruses and antiviral antibodies in vertebrate hosts: its occurrence and impacts

The recent isolation of West Nile virus from a bird in mid-winter in New York immediately raised, as one of a few explanations, the possibility of long-term persistence of arboviruses in vertebrate hosts. Although it was a highly popular topic for research many years ago, generally it has since been neglected and its meaning under appreciated. This comprehensive survey of literature worldwide uncovered, contrary to the general perception that it is a rather infrequent phenomenon, a large number of important observations involving all groups of arboviruses that have been accumulating over the years without drawing much attention. In this review, the data and observations were analysed in terms of the occurrence, role in natural transmission, mechanisms and genesis of persistence, source of problems in research and impact. The outcome of the analyses clearly demonstrates that asymptomatic, long-term infection in the absence of viraemia with or without the induction of neutralising antibody, the most frequent characteristics of arboviral persistence, presents a serious question about the validity of some of the past animal experiments that were conducted without the consideration of such a possibility. Likewise, significant impacts are felt on diverse fields ranging from epidemiology to diagnostic virology and from veterinary medicine to agricultural commerce. Published in 2001 by John Wiley & Sons, Ltd.     

Arboviruses in the Iberian Peninsula

The information concerning the presence and activity of arboviruses in the Iberian Peninsula is very scanty. In Portugal serological studies have been done with sera from animals, wild birds and human population. The results have shown that some arboviruses have been active in some areas of the territory. West Nile (WN) virus was isolated from mosquitoes and Dhori and Thogoto viruses have been isolated from ticks. In Spain, in spite of the large territory, it's geographical contiguity to Africa and the existence of different kinds of climates and ecologic conditions, the information is reduced to some surveys done in some restricted regions of the country. In both countries African swine fever was frequent and recently African horsesickness has been introduced to Southern Spain. A straight liaison and cooperation among virology laboratories of both countries and also Morocco should be emphasized in order to establish epidemiological surveillance in Southern Europe.     

Expansion des arboviroses et gestion du risque transfusionnel : exemple des virus West Nile,de la dengue et du chikungunya

Arbovirus infections are increasing in prevalence worldwide. This presents new risks for blood transfusion. This article describes the epidemiology and surveillance of West Nile Virus, dengue and chikungunya and their role in the risk management of transfusions. Arboviruses are RNA viruses and very adaptable by nature. The majority of arbovirus infections are zoonoses. The risk of transmission is multifactorial and concerns the virus, vectors, animal reservoirs, the environment and human behaviour. In recent years, West Nile Virus has become established and widespread in North America, the number of cases of dengue worldwide has increased dramatically, and major epidemics of chikungunya have occurred in the Indian Ocean and Asia. The transmission of dengue and chikungunya is demonstrated in temperate zones. All arboviruses are potentially transmissible by transfusion due to their capacity to induce an asymptomatic viremic phase. The risk of West Nile Virus transmission via transfusion is recognised and prevention measures are well established. The risk of transmission via transfusion of dengue and chikungunya is real but difficult to quantify and the optimum prevention strategy is currently the subject of research. Access to up-to-date epidemiological data is an essential aid to decision-making, especially for donors returning from endemic areas to Europe. The challenge is to define and implement appropriate measures in unpredictable situations.     

RNA interference, arthropod-borne viruses, and mosquitoes

RNA interference (RNAi) probably functions as an antiviral mechanism in most eukaryotic organisms. Variations in the activity of this antiviral pathway in mosquitoes could explain, in part, why some mosquitoes are competent vectors of medically important, arthropod-borne viruses (arboviruses) and others are not. There are three lines of evidence that show the RNAi pathway exists in Aedes species that transmit arboviruses. The first is that recombinant Sindbis viruses expressing a RNA fragment from a genetically unrelated dengue-2 virus (DENV-2) interfere with DENV-2 replication in Aedes aegypti mosquitoes by a mechanism similar to virus-induced gene silencing described in plants. The second is that transfection of C6/36 (Aedes albopictus) cells with either double-stranded RNA or synthetic small interfering RNAs derived from an arbovirus genome interferes with replication of the homologous virus. The third is that a hairpin DENV-2-specific RNA transcribed from a plasmid can generate virus-resistant C6/36 cells. We hypothesize that genetically modified mosquitoes can be generated that transcribe a flavivirus-specific dsRNA, triggering the RNAi response soon after ingestion of a blood meal. This could induce the RNAi pathway in the midgut prior to establishment of virus infection and profoundly change vector competence. Towards this goal, we are developing transgenic A. aegypti lines that are refractory to DENV by exploiting the RNAi pathway.     

The use of scanning electron microscopy in the study of haemagglutination induced by various arboviruses

Scanning electron microscopy was used to study haemagglutination by 10 arboviruses belonging to the Togaviridae and Bunyaviridae families. The pictures obtained did not allow to clarify the precise mechanism of haemagglutination by these viruses. The data suggest that no fundamental differences exist in the mechanism of haemagglutination between these two arbovirus families.     

Pathology in Malagasy lemurs and their relation to human pathology

From researches conducted in Institute Pasteur in Madagascar and from bibliographical work, the authors try to draw up a general picture of the pathology of lemurs. Several aspects are developed (bacteriology, hematology, mycology, parasitology, virology), especially those which could be interesting for human pathology, for instance the relationships between lemurs and viruses because of the arbovirus programme in progress in Institute Pasteur. The authors emphasize on the possible use of lemurs, the only non human primate in Madagascar, as laboratory animals in order to develop colonies and, then, to promote their conservation.     

Dengue virus and other arboviruses: a global view of risks

Arboviruses (arthropod-borne viruses) are an ecological group of viruses from different families (e.g. Bunyaviridae, Flaviviridae and Togaviridae) that use arthropods such as mosquitoes, flies and ticks as vectors for transmission between different hosts. The superb plasticity of these viruses allows propagation to different host systems including both invertebrates and vertebrates. More than 500 species of arbo-virus have been described and are listed in the International Catalogue of arbo-virus ( http://www.cdc.gov/nczved/divisions/dvbid/arbovirus.html ), many of which are of medical importance. Globally, arboviral infections have become increasingly common and human diseases caused by these infections have expanded their frontiers in the last few decades emerging in places with no previous history of epidemic activity or localised transmission of a specific arbovirus. One example is the recent arrival of West Nile virus (WNV) in the Western Hemisphere and its subsequent propagation in the Americas. Arboviral diseases are also re-emerging in places where the disease had previously been well-controlled or eradicated, resulting in an increasing number of cases and more severe forms of disease in endemic regions. Human infections with arboviruses are mostly asymptomatic, but symptomatic infections can range from malaise, mild febrile illness (with flu-like symptoms) to severe disease that may progress to long-term physical or cognitive impairment and/or mortality. Arboviral infections have an incubation period during which viral replication with a viremic phase takes place in the absence of symptoms. Viremic blood has the potential to transmit infection to blood recipients and therefore arboviruses can pose a threat to the safety of the blood supply. For instance, during an epidemic, asymptomatic individuals may donate blood and transmit the infection to blood component recipients. Among the arboviral infections that have been on the radar for increased activity in the last decade are: WNV, Dengue viruses (DENV) and Chikungunya virus (CHIKV). In addition, other arboviral infections such as Yellow Fever, Saint Louis encephalitis, Tick-borne encephalitis, Rift Valley fever, Japanese encephalitis, Powassan encephalitis, Murray Valley encephalitis and Zika fever have been reported as emerging or re-emerging in various areas around the globe. Alertness and surveillance are required to allow implementation of measures to mitigate risk of transmission to blood recipients including blood screening tests when available and appropriate. In addition, the evidence of increased arbovirus activity worldwide points to the critical need for the development of affordable diagnostic and screening assays with high sensitivity and specificity as well as new vaccines and therapies, since most populations at risk reside in less privileged parts of the world. The need for these tools is pressed by the imminent possibility of outbreaks in any part of the world due to the combination of expanding distribution of vectors and increased mobility of infected hosts by travel and trade.     

Establishment and characterization of a cell line from the mosquito Culex (Culex) theileri (Diptera: Culicidae) and its susceptibility to infection with arboviruses

The mosquito Culex (Culex) theileri Theobald is probably the major vector of Rift Valley fever (RVF) virus during epizootics on the inland plateau of southern Africa. A cell line was established from the tissues of this mosquito species to facilitate laboratory studies on RVF and other arboviruses. After temperature pretreatment, egg rafts from a laboratory colony were disinfected, mechanically disrupted, and grown in preconditioned Eagles minimum essential medium supplemented with 10% fetal calf serum. The cells were characterized by their protein content, karyology, and their susceptibility to three arboviruses. Although high infectivity titers were obtained, no cytopathic effects were produced by these viruses. The cell line was shown to be free from latent viruses. These results show that this cell line may be employed fruitfully in arbovirus studies.     

Laboratory preparedness and response with a focus on arboviruses in Europe

BackgroundThe global health burden of arboviruses is continuously rising, which results in increasing pressure on local and (inter)national laboratory infrastructures. Timely and accurate diagnosis of cases is one of the main pillars for public health and clinical responses to an arbovirus emergence.Aims and sourcesThis narrative review aims to summarize recent advances and to identify needs in laboratory preparedness and response activities, with a focus on viruses transmitted by arthropods in Europe. The review is based on evidence extracted from PubMed searches, Public Health and clinical laboratory experiences from the authors and the authors' opinions substantiated by peer-reviewed scientific literature.ContentWe illustrate the importance of inter-epidemic laboratory preparedness activities to ensure adequate Public Health and clinical responses. We describe the status of arbovirus endemicity and emergence in Europe thereby highlighting the need for preparedness for these viruses. We discuss the components and pitfalls of an adequate laboratory preparedness and response and the broader context of the current landscape of international research, clinical and laboratory preparedness networks. The complexity of arbovirus laboratory preparedness and response is described.ImplicationsOutbreak preparedness plans need to look beyond national reference laboratories, to include first-line responding onsite hospital laboratories and plans for strengthening of such local capacity and capability as required depending on the nature of the outbreak. In particular, the diagnosis of arbovirus infections is complicated by the existence of geographic overlap of circulation of numerous arboviruses, the overlap in clinical manifestation between many arboviruses and other aetiologies and the existence of cross-reactivity between related arboviruses in serology testing. Inter-epidemic preparedness activities need strong national and international networks addressing these issues. However, the current mushrooming of European preparedness networks requires governance to bring the European preparedness and response to a next level.     

Venezuelan Virology Network

In November 2004, sponsored by the World Bank, the Venezuelan Foundation of Science, Technology and Innovation (Fonacit) and the Venezuelan Institute of Scientific Research (IVIC), delegates from the different virology research groups of the country, met in Caracas-Venezuela, with the aim to establish the "Venezuelan Virology Network". The symposium entitled "Molecular biology applied to virus of health importance in Venezuela", was divided into three areas, including human and animals viruses related to public health: 1) Dengue, others arboviruses and Hemorrhagic Fevers; 2) diarrhea-related and others veterinary viruses and 3) Hepatitis, HIV and others sexually transmitted viruses. This symposium allowed the delegates to evaluate the current strengths, weaknesses and needs of the different laboratories, becoming evident the necessity of developing collaborative work between the groups that share the same interests or lines of research; and also their need to exchange technical resources, human and bibliographical material and consequently, avoiding the duplication of efforts and the unnecessary cost of resources. One of the main strengths of Venezuelan virology is the presence, in most laboratories, of researchers with studies of fourth level and multidisciplinary teams of work. We aspire to achieve the raised objectives in the event, to the benefit of our virology and even more important, of our people.     

Mosquito (Diptera: Culicidae) and arbovirus activity on the south coast of New South Wales, Australia, in 1985-1988.

An investigation of the seasonal activity of adult mosquitoes and arboviruses in two native forests revealed a mosquito fauna comprising 33 species for the Mogo State Forest-Batemans Bay locality and 34 species for the Termeil State Forest. The mosquito Aedes vigilax was the most abundant species in salt marshes at Mogo State Forest-Batemans Bay, whereas the freshwater species Anopheles annulipes s.l. and Coquillettidia linealis were most abundant at Termeil State Forest. Major faunal differences between the two environments reflected the extensive saline marsh and mudflat estuarine habitats at Batemans Bay and the predominantly freshwater stream, marsh, and lake habitats of Termeil State Forest. A total of 218 virus isolates was recovered from the mosquitoes, comprising Ross River virus (86 isolates), Gan Gan virus (123 isolates), Termeil virus (2 isolates), and 7 unidentified viruses. The period of greatest arbovirus activity was from midsummer through midautumn and coincided with the overall peak activity of the most common mosquito species. Ae. vigilax yielded most isolates of Ross River and Gan Gan viruses and appeared to be the vector of greatest public health concern.     

Human arbovirus infections in Burundi: results of a seroepidemiologic survey, 1980-1982

A serological survey on 623 human sera was conducted in Burundi in 1980-1982, in order to evaluate the frequency of arboviral antibodies in the inhabitants of the three main areas: lowlands, central plateau and mountainous ridge. The results show a rather high activity of arboviruses, mainly in the lowlands (34.2% of inhabitants with antibodies). Chikungunya virus seems to be the most active arbovirus; the activity of Flavivirus is moderate; no trace of activity of yellow fever or West Nile viruses was found; Bunyavirus antibodies (particularly against Ilesha virus) were also detected.     

Initiating arbovirus surveillance in Arkansas, 2001

Migratory birds could introduce West Nile (WN) virus to Arkansas. The purpose of this study was to establish a cooperative arbovirus surveillance program to monitor mosquitoes and birds in Arkansas for arboviruses. Our objectives were to: 1) perform routine, multicounty collections of mosquitoes and test them for eastern equine encephalitis, St. Louis encephalitis, and WN viruses; and 2) conduct passive surveillance by testing dead wild birds for WN virus. Arbovirus surveillance was organized by the Arkansas Department of Health, University of Arkansas, and Vector Disease Control Incorporated. None of the 14,560 mosquitoes (425 pools) tested were virus positive. Two hundred forty-two dead birds from 62 counties were tested for WN virus. Four blue jays in three counties were positive. These infections are the first reported incidences of WN virus in Arkansas. Sera from five horses with suspected encephalitis all tested negative for WN, eastern equine encephalitis, and western equine encephalitis viruses.     

Cell cultures for diagnosis of arbovirus infections in livestock and wildlife

Summary Arboviruses can be isolated in serially propagated cells derived from various vertebrates and invertebrates. Cell cultures can be used for direct detection of antigen by fluorescent antibody and enzyme-linked immunosorbent assays, for nucleic acid hybridization, and for visualization of viruses with electron microscopy. Reagents for enzyme-linked immunosorbent assays for IgM and IgG antibodies, hemagglutination-inhibition, complement fixation, and serum dilution-plaque reduction neutralization tests can be prepared in cell cultures infected with these viruses. Thus, cell cultures can be used as laboratory hosts for essentially all isolation, identification, and serodiagnostic procedures for arboviruses. This paper outlines current methods for diagnosis of arbovirus infections in livestock and wildlife, describes certain of these techniques, and provides references for others.