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We generated nine coding-complete chikungunya virus genome sequences from blood samples collected during the early 2015 outbreak in Bolivia. Relative to other publicly available chikungunya sequences, the Bolivian samples represent a monophyletic group, suggesting that a single lineage was widely circulating in the country between February and May 2015.

Here we propose a strategy allowing implementing efficient and practicable large-scale seroepidemiological studies for Zika Virus (ZIKV). It combines screening by a commercial NS1 protein-based Zika IgG ELISA, and confirmation by a cytopathic effect-based virus neutralization test (CPE-based VNT). In post-epidemic samples from Martinique Island blood donors (a population with a dengue seroprevalence above 90%), this strategy allowed reaching specificity and sensitivity values over 98%. The CPE-based VNT consists of recording CPE directly under the optical microscope, which is easy to identify with ZIKV strain H/PF/2013 at day 5 pi. Overall, considered that CPE-based VNT is cost effective and widely automatable, the NS1 protein-based Zika IgG ELISA+CPE-based VNT combination strategy represents a convenient tool to expedite ZIKV seroprevalence studies. Electronic supplementary material The online version of this article (10.1186/s12985-018-1105-5) contains supplementary material, which is available to authorized users.

Background Zika virus (ZIKV), was widely reported in Latin America and has been associated with neuropathologies, as microcephaly, but only few seroprevalence studies have been published to date. Our objective was to determine the seroprevalence amongst Bolivian blood donors and estimate the future potential circulation of the virus. Methodology A ZIKV seroprevalence study was conducted between December 2016 and April 2017 in 814 asymptomatic Bolivian volunteer blood donors residing in various eco-environments corresponding to contrasting entomological activities. It was based on detection of IgG to ZIKV using NS1 ELISA screening, followed by a seroneutralisation test in case of positive or equivocal ELISA result. Conclusions/Significance Analysis revealed that ZIKV circulation occurred in tropical areas (Beni: 39%; Santa Cruz de la Sierra: 21.5%) but not in highlands (~0% in Cochabamba, La Paz, Tarija). It was modulated by Aedes aegypti activity and the virus spread was not limited by previous immunity to dengue. Cases were geo-localised in a wide range of urban areas in Santa Cruz and Trinidad. No differences in seroprevalence related to gender or age-groups could be identified. It is concluded that ZIKV has been intensely circulating in the Beni region and has still a significant potential for propagating in the area of Santa Cruz., Author summary Zika virus (ZIKV) is a virus of African origin, transmitted by Aedes mosquitoes, and related to dengue and yellow fever virus. It was originally believed to be responsible for a mild febrile illness in Africa and South-east Asia. However, in recent years, ZIKV has been responsible for outbreaks in the Pacific Islands before massively spreading in Latin America and the Caribbean. On this occasion, ZIKV has unexpectedly been associated with non-vector transmission (i.e., sexual and mother-to-foetus transmission) and with severe complications such as foetal abnormalities (e.g. microcephaly) and Guillain-Barré syndromes. Little is known about the actual proportion of the populations infected by ZIKV in Latin America. Here, we report a seroprevalence data in this region, after studying 814 asymptomatic Bolivian volunteer blood donors residing in various eco-environments corresponding to contrasting entomological activities. We conclude that ZIKV has been circulating in Bolivian tropical areas but not in highlands, and that the epidemic has not been limited by previous immunity against dengue. Specific attention should be paid to the region of Santa Cruz, where the seroprevalence is still limited, but the density of Aedes aegypti populations makes plausible further spreading of the disease.

International audience; Here we propose a strategy allowing implementing efficient and practicable large-scale seroepidemiological studies for Zika Virus (ZIKV). It combines screening by a commercial NS1 protein-based Zika IgG ELISA, and confirmation by a cytopathic effect-based virus neutralization test (CPE-based VNT). In post-epidemic samples from Martinique Island blood donors (a population with a dengue seroprevalence above 90%), this strategy allowed reaching specificity and sensitivity values over 98%. The CPE-based VNT consists of recording CPE directly under the optical microscope, which is easy to identify with ZIKV strain H/PF/2013 at day 5 pi. Overall, considered that CPE-based VNT is cost effective and widely automatable, the NS1 protein-based Zika IgG ELISA+CPE-based VNT combination strategy represents a convenient tool to expedite ZIKV seroprevalence studies.

Dengue fever represents a major public health problem. Both viral and host immune factors are involved in severe infections. Humans and mosquito-vectors are infected with diverse viral populations that may play a role in viral adaptation and disease pathogenesis. Our objective was to analyse the intra-host genetic variability of dengue virus type 1 (DENV-1) in the venous and capillary blood and its relationships with the clinical presentation of dengue fever. Early serum samples were collected in 2009 from ten DENV-1-infected patients hospitalized in Santa Cruz de la Sierra, Bolivia. Partial viral envelope sequences were analysed at the inter-host and intra-host level. For each patient, an average of 56 clone sequences was analysed both in the venous sector and the capillary sector (from right and left hands). The ten consensus sequences were highly similar. The intra-host DENV-1 genetic variability was significantly lower in the venous sector than in the capillary sector, and in patients with haemorrhagic symptoms than in those without haemorrhagic symptoms, particularly in capillary samples. No relation was found with sex, age, dengue IgG-serological status, day of serum sampling, or viral load. Significant relationships were found between the clinical presentation of dengue fever and the variability of viral populations within hosts, particularly in capillary samples. The observed variability of envelope sequences at the early phase of dengue infection was not critically influenced by the previous dengue serological status of patients. An important part of viral microevolution may occur in the capillary sector and influence the mechanisms of severe forms.

International audience; Background: Acute respiratory infections represent a serious public health issue worldwide but virological aetiologies of Influenza Like Illnesses (ILIs) remain largely unknown in developing countries. This study represents the first attempt to characterise viral aetiologies of ILIs in Bolivia. Methods: It was performed in Santa Cruz city from January 2010 to September 2012, based on 564 naso pharyngeal swabs collected in a National Reference Laboratory and real-time PCR techniques, viral cultures and phylogenetic analyses. Results: 50.2% of samples were positive for at least one virus with influenza viruses (Flu A: similar to 15%; Flu B: similar to 9%), rhinoviruses (similar to 8%), coronaviruses (similar to 5%) and hRSV (similar to 4%) being the most frequently identified. The pattern of viral infections varied according to age groups. The elucidation rate was the highest (>60%) amongst patients under 10 yo and the lowest (= 60 yo. Nearly 3% of samples showed dual viral infections. Epidemiological peaks were associated with a predominant virus but generally included 30-50% of infections by different viruses. Unexpectedly, the frequency of influenza in the 0-4 yo population was very low and a complete hRSV eclipse occurred in 2011. Genetic analyses indicated that distinct evolutionary lineages of Flu A(H1N1)pdm2009, Flu A/H3N2 and Flu B have co-circulated in Bolivia in the study period, originating from Central and North America, Europe, Asia and Australia. Conclusion: Our results emphasise the requirement for a reinforced epidemiological and genetic follow-up of influenza and other ILIs in Bolivia to further inform the preparation of vaccines used in the region, guide vaccination campaigns and improve the medical management of patients.

Background The spread of Aedes albopictus, a vector for re-emergent arbovirus diseases like chikungunya and dengue, points up the need for better control strategies and new tools to evaluate transmission risk. Human antibody (Ab) responses to mosquito salivary proteins could represent a reliable biomarker for evaluating human-vector contact and the efficacy of control programs. Methodology/Principal Findings We used ELISA tests to evaluate specific immunoglobulin G (IgG) responses to salivary gland extracts (SGE) in adults exposed to Aedes albopictus in Reunion Island. The percentage of immune responders (88%) and levels of anti-SGE IgG Abs were high in exposed individuals. At an individual level, our results indicate heterogeneity of the exposure to Aedes albopictus bites. In addition, low-level immune cross-reactivity between Aedes albopictus and Aedes aegypti SGEs was observed, mainly in the highest responders. Conclusion/Significance Ab responses to saliva could be used as an immuno-epidemiological tool for evaluating exposure to Aedes albopictus bites. Combined with entomological and epidemiological methods, a “salivary” biomarker of exposure to Aedes albopictus could enhance surveillance of its spread and the risk of arbovirus transmission, and could be used as a direct tool for the evaluation of Aedes albopictus control strategies., Author Summary Aedes-borne viruses like dengue and chikungunya are a major problem in Reunion Island. Assessing exposure to Aedes bites is crucial to estimating the risk of pathogen transmission. Currently, the exposure of populations to Aedes albopictus bites is mainly evaluated by entomological methods which are indirect and difficult to apply on a large scale. Recent findings suggest that evaluation of human antibody responses against arthropod salivary proteins could be useful in assessing exposure to mosquito bites. The results indicate that 88% of the studied population produce IgG to Ae. albopictus saliva antigens in Reunion Island and show that this biomarker can detect different levels of individual exposure. In addition, little cross-reactivity is observed with Aedes aegypti saliva, suggesting that this could be a specific marker for exposure to Aedes albopictus bites. Taken together, these results suggest that antibody responses to saliva could constitute a powerful immuno-epidemiological tool for evaluating exposure to Aedes albopictus and therefore the risk of arbovirus infection.

Dengue fever was first recognized in Bolivia in 1931. However, very limited information was available to date regarding the genetic characterization and epidemiology of Bolivian dengue virus strains. Here, we performed genetic characterization of the full-length envelope gene of 64 Bolivian isolates from 1998 to 2008 and investigated their origin and evolution to determine whether strains circulated simultaneously or alternatively, and whether or not multiple introductions of distinct viral variants had occurred during the period studied. We determined that, during the last decade, closely related viruses circulated during several consecutive years (5, 6, and 6 years for DENV-1, DENV-2, and DENV-3, respectively) and the co-circulation of two or even three serotypes was observed. Emergence of new variants (distinct from those identified during the previous episodes) was identified in the case of DENV-1 (2007 outbreak) and DENV-2 (2001 outbreak). In all cases, it is likely that the viruses originated from neighboring countries.

Comparison of CPE-based Virus Neutralization Titre100 and PRNT90 titres. (DOCX 168 kb)

Comparison of CPE-based Virus Neutralization Titre100 and PRNT50 titres. (DOCX 172 kb)

Comparison of CPE-based Virus Neutralization Titre100 and PRNT50 titres. (DOCX 172 kb)

Comparison of CPE-based Virus Neutralization Titre100 and PRNT90 titres. (DOCX 168 kb)