Challenges towards serologic diagnostics of emerging arboviruses.

BACKGROUND: Appropriate laboratory diagnostics for emerging arboviruses are key for patient management, surveillance and intervention, including molecular tests and serological tests detecting viral antigen or virus-specific antibodies. OBJECTIVES: We provide an overview of the challenges towards serological testing for the most important emerging arboviruses, including Zika, dengue and chikungunya viruses. SOURCES: We retrieved a data set on performance of commercially available antibody- and antigen-detecting tests from 89 peer-reviewed articles conducting a systematic literature research in PubMed. CONTENT: We identified commonly used antibody- and antigen-detecting tests and analysed their overall performance. We discuss how timing of serological testing and the use of paired samples from acute and convalescent phases of infection are crucial to optimize diagnostic sensitivity and specificity. We then exemplify how serological diagnostics are challenged by the patient's infection history through the 'original antigenic sin' and cross-reactive antibodies in the context of global co-circulation of antigenically related viruses. We highlight how individual infection histories with different arboviruses and with other pathogens such as herpes viruses and Plasmodia can produce inaccurate test results. We show that rapid tests for antibody and antigen detection in point-of-care settings have a significantly lower sensitivity compared with laboratory-based tests such as ELISA. We show that the performance of antibody- and antigen-detecting tests varies greatly between tropical regions of endemic transmission and non-endemic regions. Finally, we highlight that test sensitivity and specificity have to be equilibrated carefully and frequently either of them must be prioritized over the other, depending on disease prevalence and intended use of tests. IMPLICATIONS: For reliable serological diagnostics, it is essential to be aware of inherent test limitations. Although multiplexed testing and testing of convalescence samples can improve diagnostic performance, global spread of (re-)emerging viruses requires careful implementation and evaluation of serological testing and unambiguous results may not always be achievable.

Vertebrate-Aedes aegypti and Culex quinquefasciatus (Diptera)-arbovirus transmission networks: Non-human feeding revealed by meta-barcoding and next-generation sequencing.

BACKGROUND: Aedes aegypti mosquito-borne viruses including Zika (ZIKV), dengue (DENV), yellow fever (YFV), and chikungunya (CHIKV) have emerged and re-emerged globally, resulting in an elevated burden of human disease. Aedes aegypti is found worldwide in tropical, sub-tropical, and temperate areas. The characterization of mosquito blood meals is essential to understand the transmission dynamics of mosquito-vectored pathogens. METHODOLOGY/PRINCIPAL FINDINGS: Here, we report Ae. aegypti and Culex quinquefasciatus host feeding patterns and arbovirus transmission in Northern Mexico using a metabarcoding-like approach with next-generation deep sequencing technology. A total of 145 Ae. aegypti yielded a blood meal analysis result with 107 (73.8%) for a single vertebrate species and 38 (26.2%) for two or more. Among the single host blood meals for Ae. aegypti, 28.0% were from humans, 54.2% from dogs, 16.8% from cats, and 1.0% from tortoises. Among those with more than one species present, 65.9% were from humans and dogs. For Cx. quinquefasciatus, 388 individuals yielded information with 326 (84%) being from a single host and 63 (16.2%) being from two or more hosts. Of the single species blood meals, 77.9% were from dogs, 6.1% from chickens, 3.1% from house sparrows, 2.4% from humans, while the remaining 10.5% derived from other 12 host species. Among those which had fed on more than one species, 11% were from dogs and humans, and 89% of other host species combinations. Forage ratio analysis revealed dog as the most over-utilized host by Ae. aegypti (= 4.3) and Cx. quinquefasciatus (= 5.6) and the human blood index at 39% and 4%, respectively. A total of 2,941 host-seeking female Ae. aegypti and 3,536 Cx. quinquefasciatus mosquitoes were collected in the surveyed area. Of these, 118 Ae. aegypti pools and 37 Cx. quinquefasciatus pools were screened for seven arboviruses (ZIKV, DENV 1-4, CHIKV, and West Nile virus (WNV)) using qRT-PCR and none were positive (point prevalence = 0%). The 95%-exact upper limit confidence interval was 0.07% and 0.17% for Ae. aegypti and Cx. quinquefasciatus, respectively. CONCLUSIONS/SIGNIFICANCE: The low human blood feeding rate in Ae. aegypti, high rate of feeding on mammals by Cx. quinquefasciatus, and the potential risk to transmission dynamics of arboviruses in highly urbanized areas of Northern Mexico is discussed.

Plasma virome of 781 Brazilians with unexplained symptoms of arbovirus infection include a novel parvovirus and densovirus.

Plasma from patients with dengue-like symptoms was collected in 2013 to 2016 from the Brazilian states of Tocantins and Amapa. 781 samples testing negative for IgM against Dengue, Zika, and Chikungunya viruses and for flaviviruses, alphaviruses and enteroviruses RNA using RT-PCRs were analyzed using viral metagenomics. Viral particles-associated nucleic acids were enriched, randomly amplified, and deep sequenced in 102 mini-pools generating over 2 billion reads. Sequence data was analyzed for the presence of known and novel eukaryotic viral reads. Anelloviruses were detected in 80%, human pegivirus 1 in 19%, and parvovirus B19 in 17% of plasma pools. HIV and enteroviruses were detected in two pools each. Previously uncharacterized viral genomes were also identified, and their presence in single plasma samples confirmed by PCR. Chapparvovirus and ambidensovirus genomes, both in the Parvoviridae family, were partially characterized showing 33% and 34% identity in their NS1 sequences to their closest relative. Molecular surveillance using pre-existing plasma from febrile patients provides a readily scalable approach for the detection of novel, potentially emerging, viruses.

Nanostructured impedimetric lectin-based biosensor for arboviruses detection.

Arboviruses have been emerging as a significant global health problem due to the recurrent epidemics. Arboviruses require the development of new diagnostic devices due to the nonspecific clinical manifestations. Herein, we report a biosensor based on cysteine (Cys), zinc oxide nanoparticles (ZnONp), and Concanavalin A (ConA) lectin to differentiate between arboviruses infections. ConA is capable of interacting with the saccharide components of the viral capsid. In this study, we evaluated the reproducibility, sensitivity, and specificity of the sensor for the virus of Dengue type 2 (DENV2), Zika (ZIKV), Chikungunya (CHIKV), and Yellow fever (YFV). Atomic force microscopy measurements confirmed the electrode surface modification and revealed a heterogeneous topography during the biorecognition process. Cyclic voltammetry (CV) and impedance spectroscopy (EIS) were used to characterize the biosensor. The blockage of the oxidation-reduction process is related to the formation of Cys-ZnONp-ConA system on the electroactive area and its subsequent interaction with viral glycoproteins. The sensor exhibited a linear response to different concentrations of the studied arboviruses. Our study demonstrates that ConA lectin recognizes the structural glycoproteins of the DENV2, ZIKV, CHIKV, and YFV. DENV2 is the most structurally similar to ZIKV. Our results have shown that the impedimetric response correlates with the structural glycoproteins, as follow: DENV2 (18.6 kΩ) > ZIKV (14.6 kΩ) > CHIKV (6.86 kΩ) > YFV (5.98 kΩ). The homologous structural regions contribute to ConA-arboviruses recognition. Our results demonstrate the use of the proposed system for the development of biosensors for arboviruses infections.

Successive blood meals enhance virus dissemination within mosquitoes and increase transmission potential.

The recent Zika virus (ZIKV) and chikungunya virus epidemics highlight the explosive nature of arthropod-borne viruses (arboviruses) transmitted by Aedes spp. mosquitoes1,2. Vector competence and the extrinsic incubation period (EIP) are two key entomological parameters used to assess the public health risk posed by arboviruses3. These are typically measured empirically by offering mosquitoes an infectious blood meal and temporally sampling mosquitoes to determine the infection and transmission status. This approach has been used for the better part of a century; however, it does not accurately capture the biology and behaviour of many mosquito vectors that refeed frequently (every 2-3 d)4. Here, we demonstrate that acquisition of a second non-infectious blood meal significantly shortens the EIP of ZIKV-infected Aedes aegypti by enhancing virus dissemination from the mosquito midgut. Similarly, a second blood meal increases the competence of this species for dengue virus and chikungunya virus as well as Aedes albopictus for ZIKV, suggesting that this phenomenon may be common among other virus-vector pairings and that A. albopictus might be a more important vector than once thought. Blood-meal-induced microperforations in the virus-impenetrable basal lamina that surrounds the midgut provide a mechanism for enhanced virus escape. Modelling of these findings reveals that a shortened EIP would result in a significant increase in the basic reproductive number, R0, estimated from experimental data. This helps to explain how A. aegypti can sustain explosive epidemics such as ZIKV despite relatively poor vector competence in single-feed laboratory trials. Together, these data demonstrate a direct and unrecognized link between mosquito feeding behaviour, EIP and vector competence.

Selected arboviral diseases imported to Poland - current state of knowledge and perspectives for research.

INTRODUCTION: Arthropod-borne viruses are important causes of human morbidity worldwide. However, the available literatur and the epidemiological data concerning the importation to Poland of globally emerging arboviral infections, such as DENV, CHIKV, WNV, or ZIKV, are scarce. Only few seroepidemiologic studies concerning WNV in animals or humans in Poland have been published. OBJECTIVE: The aim of this review paper is to summarize and present the current state of knowledge and the perspectives for research concerning the importation and the risk posed by the introduction to Poland of the four above-mentioned arboviral diseases. CURRENT STATE OF KNOWLEDGE: Climate change may facilitate the northward expansion of both the vectors for diseases previously unseen in Europe, as well as of the viruses themselves, resulting in autochthonous cases of diseases previously exclusively imported. Little is known about the importation of arboviral diseases to Poland because of the frequently asymptomatic or self-limiting course of the disease, lack of epidemiologic studies or effective disease reporting, as well as inadequate access to diagnostic methods. CONCLUSIONS: Further epidemiologic studies in Polish travellers are necessary in order to prevent importation or introduction of the above-mentioned viruses, and to act against potential problems related to blood transfusion or organ transplantation from infected donors.

Diagnostic Value of Platelet and Leukocyte Counts in the Differential Diagnosis of Fever in the Returning Traveler.

Malaria, arbovirus infection and travelers' diarrhea are among the most common etiologies of fever after a stay in the tropics. Because the initial symptoms of these diseases often overlap, the differential diagnostic remains a challenge. The aim of this study was to establish the effectiveness of platelet and leukocyte counts in the differential diagnosis of fever in the returning traveler. Between 2013 and 2016, patients with a clinical suspicion of malaria, who had thick blood smears performed were retrospectively included. The microbiological etiology of each episode was established based on molecular detection in the case of arbovirus infection, the detection of pathogens in stool samples for diarrhea and other gastrointestinal symptoms and the thick and thin blood smear results for malaria. A total of 1,218 episodes were included. Malaria, arbovirus infection, and diarrhea and other gastrointestinal symptoms caused 102 (8.4%), 68 (5.6%), and 72 (5.9%) episodes, respectively. The median platelet counts in malaria episodes were 89 × 109/L and thrombocytopenia (< 150,000 × 109 platelets/L) yielded a 98% negative predictive value to predict malaria. The median leukocyte counts in arbovirus infection episodes were 3.19 × 109/L and leucopenia (< 4 × 109 leukocytes/L) yielded a 97.9% negative predictive value to predict arbovirus infections. Platelet and leukocyte counts were not significantly altered in episodes caused by diarrhea and other gastrointestinal symptoms. Initial platelet and leukocyte counts might be useful for the clinical differential diagnosis of fever in the returning traveler. Although these results are insufficient to establish a diagnosis, they should be considered in the initial clinical assessment.

The PAGODAS protocol: pediatric assessment group of dengue and Aedes saliva protocol to investigate vector-borne determinants of Aedes-transmitted arboviral infections in Cambodia.

BACKGROUND: Mosquito-borne arboviruses, like dengue virus, continue to cause significant global morbidity and mortality, particularly in Southeast Asia. When the infectious mosquitoes probe into human skin for a blood meal, they deposit saliva containing a myriad of pharmacologically active compounds, some of which alter the immune response and influence host receptivity to infection, and consequently, the establishment of the virus. Previous reports have highlighted the complexity of mosquito vector-derived factors and immunity in the success of infection. Cumulative evidence from animal models and limited data from humans have identified various vector-derived components, including salivary components, that are co-delivered with the pathogen and play an important role in the dissemination of infection. Much about the roles and effects of these vector-derived factors remain to be discovered. METHODS/DESIGN: We describe a longitudinal, pagoda (community)-based pediatric cohort study to evaluate the burden of dengue virus infection and document the immune responses to salivary proteins of Aedes aegypti, the mosquito vector of dengue, Zika, and chikungunya viruses. The study includes community-based seroprevalence assessments in the peri-urban town of Chbar Mon in Kampong Speu Province, Cambodia. The study aims to recruit 771 children between the ages of 2 and 9 years for a three year period of longitudinal follow-up, including twice per year (rainy and dry season) serosurveillance for dengue seroconversion and Ae. aegypti salivary gland homogenate antibody intensity determinations by ELISA assays. Diagnostic tests for acute dengue, Zika and chikungunya viral infections will be performed by RT-PCR. DISCUSSION: This study will serve as a foundation for further understanding of mosquito saliva immunity and its impact on Aedes-transmitted arboviral diseases endemic to Cambodia. TRIAL REGISTRATION: NCT03534245 registered on 23 May 2018.

Arboviral Surveillance among Pediatric Patients with Acute Febrile Illness in Houston, Texas.

We instituted active surveillance among febrile patients presenting to the largest Houston-area pediatric emergency department to identify acute infections of dengue virus (DENV), West Nile virus (WNV), and chikungunya virus (CHIKV). In 2014, 1,063 children were enrolled, and 1,015 (95%) had blood and/or cerebrospinal fluid specimens available for DENV, WNV, and CHIKV testing. Almost half (49%) reported recent mosquito bites, and 6% (N = 60) reported either recent international travel or contact with an international traveler. None were positive for acute WNV; three had false-positive CHIKV results; and two had evidence of DENV. One DENV-positive case was an acute infection associated with international travel, whereas the other was identified as a potential secondary acute infection, also likely travel-associated. Neither of the DENV-positive cases were clinically recognized, highlighting the need for education and awareness. Health-care professionals should consider the possibility of arboviral disease among children who have traveled to or from endemic areas.

Reliable Serological Testing for the Diagnosis of Emerging Infectious Diseases.

Climate change, increased urbanization and international travel have facilitated the spread of mosquito vectors and the viral species they carry. Zika virus (ZIKV) is currently spreading in the Americas, while dengue virus (DENV) and chikungunya virus (CHIKV) have already become firmly established in most tropical and also many non-tropical regions. ZIKV, DENV and CHIKV overlap in their endemic areas and cause similar clinical symptoms, especially in the initial stages of infection. Infections with each of these viruses can lead to severe complications, and co-infections have been reported. Therefore, laboratory analyses play an important role in differential diagnostics. A timely and accurate diagnosis is crucial for patient management, prevention of unnecessary therapies, rapid adoption of vector control measures, and collection of epidemiological data.There are two pillars to diagnosis: direct pathogen detection and the determination of specific antibodies. Serological tests provide a longer diagnostic window than direct methods, and are suitable for diagnosing acute and past infections, for disease surveillance and for vaccination monitoring. ELISA and indirect immunofluorescence test (IIFT) systems based on optimized antigens enable sensitive and specific detection of antibodies against ZIKV, DENV and CHIKV in patient serum or plasma. In recent years, Euroimmun (Lübeck, Germany) has developed numerous test systems for the serological diagnosis of (re-)emerging diseases, including a very sensitive and specific anti-ZIKV ELISA.

Seroepidemiological Studies of Arboviruses in Africa.

The literature on sero-epidemiological studies of flaviviral infections in the African continent is quite scarce. Much of the viral epidemiology studies have been focussing on diseases such as HIV/AIDS because of their sheer magnitude and impact on the lives of people in the various affected countries. Increasingly disease outbreaks caused by arboviruses such as the recent cases of chikungunya virus, dengue virus and yellow fever virus have prompted renewed interest in studying these viruses. International agencies from the US, several EU nations and China are starting to build collaborations to build capacity in many African countries together with established institutions to conduct these studies. The Tofo Advanced Study Week (TASW) was established to bring the best scientists from the world to the tiny seaside town of Praia do Tofo to rub shoulders with African virologists and discuss cutting-edge science and listen to the work of researchers in the field. In 2015 the 1st TASW focussed on Ebola virus. The collections of abstracts from participants at the 2nd TASW which focused on Dengue and Zika virus as well as presentations on other arboviruses are collated in this chapter.

Seroprevalence survey of arboviruses in workers from Tuscany, Italy.

BACKGROUND: Arthropod-borne viruses (Arbovirus) play an important role among emerging and re-emerging infectious diseases and in the spreading of infections in new geographic areas. Although some arboviral infections may be asymptomatic or mild flu-like illnesses, many occur as severe forms of meningitis and meningoencephalitis. OBJECTIVES: To assess whether arboviral infections may be associated with occupational risk, in a population of agricultural and forestry workers potentially at high risk for arthropods bite and sting. METHODS: A seroprevalence survey for arboviruses belonging to the genera Flaviviruses (West Nile, Tick-borne encephalitis and Usutu viruses) and Phlebovirus (Toscana virus) was carried out in Grosseto province (Tuscany, Italy). One hundred and one serum samples of occupationally exposed workers and 100 serum samples of not exposed workers were analyzed using commercial and home-made serological assays. Serological data were obtained in 2012 and analyzed according to demographic characteristics, recollection of insect-bites, and time spent in outdoor activities. RESULTS: A total seropositivity of 10% (21/201) was observed for Toscana virus. No difference in seroprevalence for Toscana virus was observed among the exposed (10/101) versus the not exposed (11/100) workers. No seropositivity for West Nile, Usutu and Tick-borne encephalitis viruses was detected. CONCLUSIONS: Although circulation of Toscana virus is recognized in the study area, our results did not reveal a higher risk for workers exposed to arthropods bite and sting. Health surveillance programs remain useful to monitor the potential emergence of arboviruses.

A simulation model to estimate the risk of transfusion-transmitted arboviral infection.

BACKGROUND: The arboviruses West Nile virus (WNV), dengue virus (DENV) and Ross River virus (RRV) have been demonstrated to be blood transfusion-transmissible. A model to estimate the risk of WNV to the blood supply using a Monte Carlo approach has been developed and also applied to Chikungunya virus. Also, a probabilistic model was developed to assess the risk of DENV to blood safety, which was later adapted to RRV. To address efficacy and limitations within each model we present a hybrid model that promises improved accuracy, and is broadly applicable to assess the risk of arboviral transmission by blood transfusion. MATERIAL AND METHODS: Data were drawn from the Cairns Public Health Unit (Australia) and published literature. Based on the published models and using R code, a novel 'combined' model was developed and validated against the BP model using sensitivity testing. RESULTS: The mean risk per 10,000 of the combined model is 0.98 with a range from 0.79 to 1.25, while the maximum risk was 4.45 ranging from 2.62 to 7.67 respectively. These parameters for the BP model were 1.20 ranging from 0.84 to 1.55, and 2.86 ranging from 1.33 to 5.23 respectively. CONCLUSION: The combined simulation model is simple and robust. We propose it can be applied as a 'generic' arbovirus model to assess the risk from known or novel arboviral threats to the blood supply.

Monitoring for bovine arboviruses in the most southwestern islands in Japan between 1994 and 2014.

BACKGROUND: In Japan, epizootic arboviral infections have severely impacted the livestock industry for a long period. Akabane, Aino, Chuzan, bovine ephemeral fever and Ibaraki viruses have repeatedly caused epizootic abnormal births and febrile illness in the cattle population. In addition, Peaton, Sathuperi, Shamonda and D'Aguilar viruses and epizootic hemorrhagic virus serotype 7 have recently emerged in Japan and are also considered to be involved in abnormal births in cattle. The above-mentioned viruses are hypothesized to circulate in tropical and subtropical Asia year round and to be introduced to temperate East Asia by long-distance aerial dispersal of infected vectors. To watch for arbovirus incursion and assess the possibility of its early warning, monitoring for arboviruses was conducted in the Yaeyama Islands, located at the most southwestern area of Japan, between 1994 and 2014. RESULTS: Blood sampling was conducted once a year, in the autumn, in 40 to 60 healthy cattle from the Yaeyama Islands. Blood samples were tested for arboviruses. A total of 33 arboviruses including Akabane, Peaton, Chuzan, D' Aguilar, Bunyip Creek, Batai and epizootic hemorrhagic viruses were isolated from bovine blood samples. Serological surveillance for the bovine arboviruses associated with cattle diseases in young cattle (ages 6-12 months: had only been alive for one summer) clearly showed their frequent incursion into the Yaeyama Islands. In some cases, the arbovirus incursions could be detected in the Yaeyama Islands prior to their spread to mainland Japan. CONCLUSIONS: We showed that long-term surveillance in the Yaeyama Islands could estimate the activity of bovine arboviruses in neighboring regions and may provide a useful early warning for likely arbovirus infections in Japan. The findings in this study could contribute to the planning of prevention and control for bovine arbovirus infections in Japan and cooperative efforts among neighboring countries in East Asia.

Sero-prevalence and cross-reactivity of chikungunya virus specific anti-E2EP3 antibodies in arbovirus-infected patients.

Chikungunya virus (CHIKV) and clinically-related arboviruses cause large epidemics with serious economic and social impact. As clinical symptoms of CHIKV infections are similar to several flavivirus infections, good detection methods to identify CHIKV infection are desired for improved treatment and clinical management. The strength of anti-E2EP3 antibody responses was explored in a longitudinal study on 38 CHIKV-infected patients. We compared their anti-E2EP3 responses with those of patients infected with non-CHIKV alphaviruses, or flaviviruses. E2EP3 cross-reactive samples from patients infected with non-CHIKV viruses were further analyzed with an in vitro CHIKV neutralization assay. CHIKV-specific anti-E2EP3 antibody responses were detected in 72% to 100% of patients. Serum samples from patients infected with other non-CHIKV alphaviruses were cross-reactive to E2EP3. Interestingly, some of these antibodies demonstrated clearly in vitro CHIKV neutralizing activity. Contrastingly, serum samples from flaviviruses-infected patients showed a low level of cross-reactivity against E2EP3. Using CHIKV E2EP3 as a serology marker not only allows early detection of CHIKV specific antibodies, but would also allow the differentiation between CHIKV infections and flavivirus infections with 93% accuracy, thereby allowing precise acute febrile diagnosis and improving clinical management in regions newly suffering from CHIKV outbreaks including the Americas.

Multiplex microsphere immunoassays for the detection of IgM and IgG to arboviral diseases.

Serodiagnosis of arthropod-borne viruses (arboviruses) at the Division of Vector-Borne Diseases, CDC, employs a combination of individual enzyme-linked immunosorbent assays and microsphere immunoassays (MIAs) to test for IgM and IgG, followed by confirmatory plaque-reduction neutralization tests. Based upon the geographic origin of a sample, it may be tested concurrently for multiple arboviruses, which can be a cumbersome task. The advent of multiplexing represents an opportunity to streamline these types of assays; however, because serologic cross-reactivity of the arboviral antigens often confounds results, it is of interest to employ data analysis methods that address this issue. Here, we constructed 13-virus multiplexed IgM and IgG MIAs that included internal and external controls, based upon the Luminex platform. Results from samples tested using these methods were analyzed using 8 different statistical schemes to identify the best way to classify the data. Geographic batteries were also devised to serve as a more practical diagnostic format, and further samples were tested using the abbreviated multiplexes. Comparative error rates for the classification schemes identified a specific boosting method based on logistic regression "Logitboost" as the classification method of choice. When the data from all samples tested were combined into one set, error rates from the multiplex IgM and IgG MIAs were <5% for all geographic batteries. This work represents both the most comprehensive, validated multiplexing method for arboviruses to date, and also the most systematic attempt to determine the most useful classification method for use with these types of serologic tests.

[Immunotropic therapy of arbovirus infections in children].

Cytochemical indices of peripheral blood leukocytes were investigated. The results allowed to estimate the level of the disease severity and to control the immunotropic therapy efficacy. Dysbalance of the interleukocytic microbicidical systems (IMS) of neutrophils reflected the nonspecific resisistance and the state of the phagocytic system as an objective criterion of the adaptation syndrome. Association of the deficiency of the IMS components and blood serum fibronectin were considered as a predisposition of bacterial complications. Cycloferon activated the phagocyte metabolic activity and promoted elimination of the main clinical symptoms of the disease (acute infective damage of the meninges, temperature elevation, intoxication signs), thus making shorter the hospitalization terms.

Serologic evidence of arboviral infections among humans in Kenya.

Outbreaks of arthropod-borne viral infections occur periodically across Kenya. However, limited surveillance takes place during interepidemic periods. Using serum samples obtained from asymptomatic persons across Kenya in 2000-2004, we assessed (by indirect immunofluorescent assay) prevalence of IgG against yellow fever virus (YFV), West Nile virus (WNV), tick-borne encephalitis virus (TBEV), dengue virus serotypes 1-4 (DENV1-4), and chikungunya virus (CHIKV). Older persons on the Indian Ocean coast were more likely to be seropositive than children inland: YFV = 42% versus 6%, WNV = 29% versus 6%, TBEV = 16% versus 6%, DENV-1 = 63% versus 9%, DENV-2 = 67% versus 7%, DENV-3 = 55% versus 6%, DENV-4 = 44% versus 8%, and CHIKV = 37% versus 20%. Among inland samples, children in lowlands were more likely to be seropositive for CHIKV (42% versus 0%) than children in highlands. In Kenya, transmission of arboviral infection continues between known epidemics and remains common across the country.

[Emergent viral threats in blood transfusion]. / Risques viraux émergents en transfusion sanguine.

During the last 20 years, the safety of blood products increased dramatically with regard to the infectious risk and notably to that represented by retroviruses (HIV and HTLV) and hepatitis B and C viruses. The aim of this review is to identify the residual and emergent viral threats that could be responsible for the occurring of new contaminations in the receivers of blood products. Beside many other viruses (HHV-8, erythrovirus B19, hepatitis A and E viruses...), a special attention has been paid to emerging arbovirus diseases (West Nile virus infection, dengue, chikungunya) that threaten to occur in the French metropolitan area following the implantation in Europe of the mosquito Aedes albopictus, the main vector of dengue and chikungunya in temperate regions. Another blood-linked risk, notably in United Kingdom and France, is the prion agent responsible for the variant form of the Creutzfeldt-Jakob disease. The review is concluded by a brief overview of the measures aimed to control these emergences, including the exclusion of at-risk donors, the diagnostic tests able to detect a specific agent, the leukocyte reduction of labile blood products, and the physical or chemical treatments aiming the nonspecific inactivation of infectious agents potentially present in blood without impairing significantly the physiological properties of blood compounds. The ability to control prospectively the new viral risks linked to blood products is a challenge for the preservation of the confidence of both clinicians and receivers in the safety of blood transfusion.

Rapid screening for sentinel chicken seroconversions against arboviruses.

A novel test procedure can screen seroconversions in sentinel chickens with the commercially available VecTest designed to detect viral antigens, such as West Nile virus. The test requires minimum laboratory equipment and skills, and provides qualitative results in about 45 min, which are immediately available to vector control agencies for making decisions to manage mosquito populations in order to interrupt arbovirus transmission.