Publications by authors named "Van-Mai Cao-Lormeau"

60 Publications

Recent African strains of Zika virus display higher transmissibility and fetal pathogenicity than Asian strains.

Nat Commun 2021 02 10;12(1):916. Epub 2021 Feb 10.

Insect-Virus Interactions Unit, Institut Pasteur, UMR2000, CNRS, Paris, France.

The global emergence of Zika virus (ZIKV) revealed the unprecedented ability for a mosquito-borne virus to cause congenital birth defects. A puzzling aspect of ZIKV emergence is that all human outbreaks and birth defects to date have been exclusively associated with the Asian ZIKV lineage, despite a growing body of laboratory evidence pointing towards higher transmissibility and pathogenicity of the African ZIKV lineage. Whether this apparent paradox reflects the use of relatively old African ZIKV strains in most laboratory studies is unclear. Here, we experimentally compare seven low-passage ZIKV strains representing the recently circulating viral genetic diversity. We find that recent African ZIKV strains display higher transmissibility in mosquitoes and higher lethality in both adult and fetal mice than their Asian counterparts. We emphasize the high epidemic potential of African ZIKV strains and suggest that they could more easily go unnoticed by public health surveillance systems than Asian strains due to their propensity to cause fetal loss rather than birth defects.
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http://dx.doi.org/10.1038/s41467-021-21199-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7876148PMC
February 2021

Enhanced Zika virus susceptibility of globally invasive populations.

Science 2020 11;370(6519):991-996

Insect-Virus Interactions Unit, Institut Pasteur, UMR2000, CNRS, Paris, France.

The drivers and patterns of zoonotic virus emergence in the human population are poorly understood. The mosquito is a major arbovirus vector native to Africa that invaded most of the world's tropical belt over the past four centuries, after the evolution of a "domestic" form that specialized in biting humans and breeding in water storage containers. Here, we show that human specialization and subsequent spread of out of Africa were accompanied by an increase in its intrinsic ability to acquire and transmit the emerging human pathogen Zika virus. Thus, the recent evolution and global expansion of promoted arbovirus emergence not solely through increased vector-host contact but also as a result of enhanced vector susceptibility.
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http://dx.doi.org/10.1126/science.abd3663DOI Listing
November 2020

Long-term persistence of monotypic dengue transmission in small size isolated populations, French Polynesia, 1978-2014.

PLoS Negl Trop Dis 2020 03 6;14(3):e0008110. Epub 2020 Mar 6.

Laboratoire de recherche sur les maladies infectieuses à transmission vectorielle, Institut Louis Malardé, Papeete, Tahiti, French Polynesia.

Understanding the transition of epidemic to endemic dengue transmission remains a challenge in regions where serotypes co-circulate and there is extensive human mobility. French Polynesia, an isolated group of 117 islands of which 72 are inhabited, distributed among five geographically separated subdivisions, has recorded mono-serotype epidemics since 1944, with long inter-epidemic periods of circulation. Laboratory confirmed cases have been recorded since 1978, enabling exploration of dengue epidemiology under monotypic conditions in an isolated, spatially structured geographical location. A database was constructed of confirmed dengue cases, geolocated to island for a 35-year period. Statistical analyses of viral establishment, persistence and fade-out as well as synchrony among subdivisions were performed. Seven monotypic and one heterotypic dengue epidemic occurred, followed by low-level viral circulation with a recrudescent epidemic occurring on one occasion. Incidence was asynchronous among the subdivisions. Complete viral die-out occurred on several occasions with invasion of a new serotype. Competitive serotype replacement has been observed previously and seems to be characteristic of the South Pacific. Island population size had a strong impact on the establishment, persistence and fade-out of dengue cases and endemicity was estimated achievable only at a population size in excess of 175 000. Despite island remoteness and low population size, dengue cases were observed somewhere in French Polynesia almost constantly, in part due to the spatial structuration generating asynchrony among subdivisions. Long-term persistence of dengue virus in this group of island populations may be enabled by island hopping, although could equally be explained by a reservoir of sub-clinical infections on the most populated island, Tahiti.
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http://dx.doi.org/10.1371/journal.pntd.0008110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7080275PMC
March 2020

First evidence of concurrent enzootic and endemic transmission of Ross River virus in the absence of marsupial reservoirs in Fiji.

Int J Infect Dis 2020 Jul 27;96:94-96. Epub 2020 Feb 27.

Research School of Population Health, College of Health & Medicine, Australian National University, Canberra ACT 0200, Australia.

Background: Ross River virus (RRV) is a zoonotic alphavirus transmitted by several mosquito species. Until recently, endemic transmission was only considered possible in the presence of marsupial reservoirs.

Methods: RRV seroprevalence was investigated in placental mammals (including horses, cows, goats, pigs, dogs, rats, and mice) in Fiji, where there are no marsupials. A total of 302 vertebrate serum samples were collected from 86 households from 10 communities in Western Fiji.

Results: Neutralizing antibodies against RRV were detected in 28% to 100% of sera depending on the species, and neutralization was strong even at high dilutions.

Conclusions: These results are unlikely to be due to cross-reactions. Chikungunya is the only other alphavirus known to be present in the Pacific Islands, but it rarely spills over into non-humans, even during epidemics. The study findings, together with a recent report of high RRV seroprevalence in humans, strongly suggest that RRV is circulating in Fiji in the absence of marsupial reservoirs. Considering that all non-human vertebrates present in Fiji are pan-global in distribution, RRV has the potential to further expand its geographic range. Further surveillance of RRV and access to RRV diagnostics will be critical for the early detection of emergence and outbreaks.
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http://dx.doi.org/10.1016/j.ijid.2020.02.048DOI Listing
July 2020

Zika seroprevalence declines and neutralizing antibodies wane in adults following outbreaks in French Polynesia and Fiji.

Elife 2020 Jan 28;9. Epub 2020 Jan 28.

Centre for the Mathematical Modelling of Infectious Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.

It has been commonly assumed that Zika virus (ZIKV) infection confers long-term protection against reinfection, preventing ZIKV from re-emerging in previously affected areas for several years. However, the long-term immune response to ZIKV following an outbreak remains poorly documented. We compared results from eight serological surveys before and after known ZIKV outbreaks in French Polynesia and Fiji, including cross-sectional and longitudinal studies. We found evidence of a decline in seroprevalence in both countries over a two-year period following first reported ZIKV transmission. This decline was concentrated in adults, while high seroprevalence persisted in children. In the Fiji cohort, there was also a significant decline in neutralizing antibody titres against ZIKV, but not against dengue viruses that circulated during the same period.
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http://dx.doi.org/10.7554/eLife.48460DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6986872PMC
January 2020

Low chikungunya virus seroprevalence two years after emergence in Fiji.

Int J Infect Dis 2020 Jan 2;90:223-225. Epub 2019 Nov 2.

Institut Louis Malardé, PO BOX 30, 98713 Papeete, Tahiti, French Polynesia.

Objectives: In Fiji, autochthonous chikungunya virus (CHIKV) infection was first detected in March 2015. In a previous serosurvey conducted during October-November 2015, we reported a prevalence of anti-CHIKV IgG antibodies of 0.9%. In the present study, we investigated the seroprevalence of CHIKV two years after its emergence in Fiji.

Methods: Sera from 320 residents of Fiji recruited in June 2017, from the same cohort of individuals that participated in the serosurvey in 2015, were tested for the presence of IgG antibodies against CHIKV using a recombinant antigen-based microsphere immunoassay.

Results: Between 2015 and 2017, CHIKV seroprevalence among residents increased from 0.9% (3/333) to 12.8% (41/320). Of the participants with available serum samples collected in both 2015 and 2017 (n=200), 31 (15.5%) who were seronegative in 2015 had seroconverted to CHIKV in 2017.

Conclusions: Our findings suggest that low-level transmission of CHIKV occurred during the two years following the emergence of the virus in Fiji. No CHIKV infection has been reported in Fiji since 2017, but due to the presumed low herd immunity of the population, the risk of CHIKV re-emergence is high. Consequently, chikungunya should be considered in the differential diagnosis of acute febrile diseases in Fiji.
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http://dx.doi.org/10.1016/j.ijid.2019.10.040DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6912130PMC
January 2020

Dengue virus serotype 2 (DENV-2) outbreak, French Polynesia, 2019.

Euro Surveill 2019 Jul;24(29)

Institut Louis Malardé, Papeete, Tahiti, French Polynesia.

In 1996-97, the last dengue virus serotype 2 (DENV-2) outbreak occurred in French Polynesia. In February 2019, DENV-2 infection was detected in a traveller from New Caledonia. In March, autochthonous DENV-2 infection was diagnosed in two residents. A DENV-2 outbreak was declared on 10 April with 106 cases as at 24 June. Most of the population is not immune to DENV-2; a large epidemic could occur with risk of imported cases in mainland France.
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http://dx.doi.org/10.2807/1560-7917.ES.2019.24.29.1900407DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6652116PMC
July 2019

Sustained Low-Level Transmission of Zika and Chikungunya Viruses after Emergence in the Fiji Islands.

Emerg Infect Dis 2019 08;25(8):1535-1538

Zika and chikungunya viruses were first detected in Fiji in 2015. Examining surveillance and phylogenetic and serologic data, we found evidence of low-level transmission of Zika and chikungunya viruses during 2013-2017, in contrast to the major outbreaks caused by closely related virus strains in other Pacific Island countries.
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http://dx.doi.org/10.3201/eid2508.180524DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6649350PMC
August 2019

Cell-Fusing Agent Virus Reduces Arbovirus Dissemination in Aedes aegypti Mosquitoes .

J Virol 2019 09 28;93(18). Epub 2019 Aug 28.

Insect-Virus Interactions Unit, UMR2000, CNRS, Institut Pasteur, Paris, France

mosquitoes are the main vectors of arthropod-borne viruses (arboviruses) of public health significance, such as the flaviviruses dengue virus (DENV) and Zika virus (ZIKV). Mosquitoes are also the natural hosts of a wide range of viruses that are insect specific, raising the question of their influence on arbovirus transmission in nature. Cell-fusing agent virus (CFAV) was the first described insect-specific flavivirus, initially discovered in an cell line and subsequently detected in natural populations. It was recently shown that DENV and the CFAV strain isolated from the cell line have mutually beneficial interactions in mosquito cells in culture. However, whether natural strains of CFAV and DENV interact in live mosquitoes is unknown. Using a wild-type CFAV isolate recently derived from Thai mosquitoes, we found that CFAV negatively interferes with both DENV type 1 and ZIKV and For both arboviruses, prior infection by CFAV reduced the dissemination titer in mosquito head tissues. Our results indicate that the interactions observed between arboviruses and the CFAV strain derived from the cell line might not be a relevant model of the viral interference that we observed Overall, our study supports the hypothesis that insect-specific flaviviruses may contribute to reduce the transmission of human-pathogenic flaviviruses. The mosquito carries several arthropod-borne viruses (arboviruses) that are pathogenic to humans, including dengue and Zika viruses. Interestingly, is also naturally infected with insect-only viruses, such as cell-fusing agent virus. Although interactions between cell-fusing agent virus and dengue virus have been documented in mosquito cells in culture, whether wild strains of cell-fusing agent virus interfere with arbovirus transmission by live mosquitoes was unknown. We used an experimental approach to demonstrate that cell-fusing agent virus infection reduces the propagation of dengue and Zika viruses in mosquitoes. These results support the idea that insect-only viruses in nature can modulate the ability of mosquitoes to carry arboviruses of medical significance and that they could possibly be manipulated to reduce arbovirus transmission.
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http://dx.doi.org/10.1128/JVI.00705-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6714787PMC
September 2019

Ross River Virus Antibody Prevalence, Fiji Islands, 2013-2015.

Emerg Infect Dis 2019 04;25(4):827-830

A unique outbreak of Ross River virus (RRV) infection was reported in Fiji in 1979. In 2013, RRV seroprevalence among residents was 46.5% (362/778). Of the residents who were seronegative in 2013 and retested in 2015, 10.9% (21/192) had seroconverted to RRV, suggesting ongoing endemic circulation of RRV in Fiji.
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http://dx.doi.org/10.3201/eid2504.180694DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6433005PMC
April 2019

Zika Virus Infection during Pregnancy and Effects on Early Childhood Development, French Polynesia, 2013-2016.

Emerg Infect Dis 2018 10;24(10):1850-1858

Congenital Zika virus syndrome consists of a large spectrum of neurologic abnormalities seen in infants infected with Zika virus in utero. However, little is known about the effects of Zika virus intrauterine infection on the neurocognitive development of children born without birth defects. Using a case-control study design, we investigated the temporal association of a cluster of congenital defects with Zika virus infection. In a nested study, we also assessed the early childhood development of children recruited in the initial study as controls who were born without known birth defects,. We found evidence for an association of congenital defects with both maternal Zika virus seropositivity (time of infection unknown) and symptomatic Zika virus infection during pregnancy. Although the early childhood development assessment found no excess burden of developmental delay associated with maternal Zika virus infection, larger, longer-term studies are needed.
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http://dx.doi.org/10.3201/eid2410.172079DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6154169PMC
October 2018

Reassessing Serosurvey-Based Estimates of the Symptomatic Proportion of Zika Virus Infections.

Am J Epidemiol 2019 01;188(1):206-213

Division of Vector-Borne Diseases, Centers for Disease Control and Prevention, San Juan, Puerto Rico.

Since the 2007 Zika epidemic in the Micronesian state of Yap, it has been apparent that not all people infected with Zika virus (ZIKV) experience symptoms. However, the proportion of infections that result in symptoms remains unclear. Existing estimates have varied in their interpretation of symptoms due to other causes and the case definition used, and they have assumed perfect test sensitivity and specificity. Using a Bayesian model and data from ZIKV serosurveys in Yap (2007), French Polynesia (2013-2014), and Puerto Rico (2016), we found that assuming perfect sensitivity and specificity generally led to lower estimates of the symptomatic proportion. Incorporating reasonable assumptions for assay sensitivity and specificity, we estimated that 27% (95% credible interval (CrI): 15, 37) (Yap), 44% (95% CrI: 26, 66) (French Polynesia), and 50% (95% CrI: 34, 92) (Puerto Rico) of infections were symptomatic, with variation due to differences in study populations, study designs, and case definitions. The proportion of ZIKV infections causing symptoms is critical for surveillance system design and impact assessment. Here, we accounted for key uncertainties in existing seroprevalence data and found that estimates for the symptomatic proportion ranged from 27% to 50%, suggesting that while the majority of infections are asymptomatic or mildly symptomatic, symptomatic infections might be more common than previously estimated.
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http://dx.doi.org/10.1093/aje/kwy189DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6321808PMC
January 2019

Using paired serology and surveillance data to quantify dengue transmission and control during a large outbreak in Fiji.

Elife 2018 08 14;7. Epub 2018 Aug 14.

Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, London, United Kingdom.

Dengue is a major health burden, but it can be challenging to examine transmission and evaluate control measures because outbreaks depend on multiple factors, including human population structure, prior immunity and climate. We combined population-representative paired sera collected before and after the 2013/14 dengue-3 outbreak in Fiji with surveillance data to determine how such factors influence transmission and control in island settings. Our results suggested the 10-19 year-old age group had the highest risk of infection, but we did not find strong evidence that other demographic or environmental risk factors were linked to seroconversion. A mathematical model jointly fitted to surveillance and serological data suggested that herd immunity and seasonally varying transmission could not explain observed dynamics. However, the model showed evidence of an additional reduction in transmission coinciding with a vector clean-up campaign, which may have contributed to the decline in cases in the later stages of the outbreak.
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http://dx.doi.org/10.7554/eLife.34848DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6092126PMC
August 2018

Zika virus outbreak in the Pacific: Vector competence of regional vectors.

PLoS Negl Trop Dis 2018 07 17;12(7):e0006637. Epub 2018 Jul 17.

Institut Pasteur de Nouvelle-Calédonie, URE-Dengue et autres Arboviroses, Nouméa, New Caledonia.

Background: In 2013, Zika virus (ZIKV) emerged in French Polynesia and spread through the Pacific region between 2013 and 2017. Several potential Aedes mosquitoes may have contributed to the ZIKV transmission including Aedes aegypti, the main arbovirus vector in the region, and Aedes polynesiensis, vector of lymphatic filariasis and secondary vector of dengue virus. The aim of this study was to analyze the ability of these two Pacific vectors to transmit ZIKV at a regional scale, through the evaluation and comparison of the vector competence of wild Ae. aegypti and Ae. polynesiensis populations from different Pacific islands for a ZIKV strain which circulated in this region during the 2013-2017 outbreak.

Methodology/principal Findings: Field Ae. aegypti (three populations) and Ae. polynesiensis (two populations) from the Pacific region were collected for this study. Female mosquitoes were orally exposed to ZIKV (107 TCID50/mL) isolated in the region in 2014. At 6, 9, 14 and 21 days post-infection, mosquito bodies (thorax and abdomen), heads and saliva were analyzed to measure infection, dissemination, transmission rates and transmission efficiency, respectively. According to our results, ZIKV infection rates were heterogeneous between the Ae. aegypti populations, but the dissemination rates were moderate and more homogenous between these populations. For Ae. polynesiensis, infection rates were less heterogeneous between the two populations tested. The transmission rate and efficiency results revealed a low vector competence for ZIKV of the different Aedes vector populations under study.

Conclusion/significance: Our results indicated a low ZIKV transmission by Ae. aegypti and Ae. polynesiensis tested from the Pacific region. These results were unexpected and suggest the importance of other factors especially the vector density, the mosquito lifespan or the large immunologically naive fraction of the population that may have contributed to the rapid spread of the ZIKV in the Pacific region during the 2013-2017 outbreak.
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http://dx.doi.org/10.1371/journal.pntd.0006637DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6063428PMC
July 2018

Unexpected outbreaks of arbovirus infections: lessons learned from the Pacific and tropical America.

Lancet Infect Dis 2018 11 19;18(11):e355-e361. Epub 2018 Jun 19.

Programme in Emerging Infectious Diseases, Duke-NUS Medical School, Singapore.

Pandemic arboviruses have emerged as a major global health problem in the past four decades. Predicting where and when the next arbovirus epidemic will occur is a challenge, but history suggests that arboviral black swan events (epidemics that are difficult to predict and that have an extreme effect) will continue to occur as urban growth and globalisation expand. We briefly review unexpected arbovirus epidemics that have occurred in the past 50 years, with emphasis on the American and Pacific regions, to illustrate their unpredictability, and to highlight the need for improved global preparedness, including laboratory-based surveillance, prevention, and control programmes.
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http://dx.doi.org/10.1016/S1473-3099(18)30269-XDOI Listing
November 2018

Re-visiting the evolution, dispersal and epidemiology of Zika virus in Asia.

Emerg Microbes Infect 2018 May 9;7(1):79. Epub 2018 May 9.

UMR "Unité des Virus Emergents", Aix-Marseille Université-IRD 190-Inserm 1207-IHU Méditerranée Infection, Marseille, France.

Based on serological evidence and viral isolation, Zika virus (ZIKV) has circulated for many years relatively benignly in a sylvatic cycle in Africa and an urban cycle in South East Asia (SEA). With the recent availability of limited but novel Indian ZIKV sequences to add to the plethora of SEA sequences, we traced the phylogenetic history and spatio-temporal dispersal pattern of ZIKV in Asia prior to its explosive emergence in the Pacific region and the Americas. These analyses demonstrated that the introduction and dispersal of ZIKV on the Pacific islands were preceded by an extended period of relatively silent transmission in SEA, enabling the virus to expand geographically and evolve adaptively before its unanticipated introduction to immunologically naive populations on the Pacific islands and in the Americas. Our findings reveal new features of the evolution and dispersal of this intriguing virus and may benefit future disease control strategies.
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http://dx.doi.org/10.1038/s41426-018-0082-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5940881PMC
May 2018

Full-genome dengue virus sequencing in mosquito saliva shows lack of convergent positive selection during transmission by .

Virus Evol 2017 Jul 6;3(2):vex031. Epub 2017 Nov 6.

Insect-Virus Interactions Group, Department of Genomes and Genetics, Institut Pasteur, 28 rue du Docteur Roux, 75015 Paris, France.

Like other pathogens with high mutation and replication rates, within-host dengue virus (DENV) populations evolve during infection of their main mosquito vector, . Within-host DENV evolution during transmission provides opportunities for adaptation and emergence of novel virus variants. Recent studies of DENV genetic diversity failed to detect convergent evolution of adaptive mutations in mosquito tissues such as midgut and salivary glands, suggesting that convergent positive selection is not a major driver of within-host DENV evolution in the vector. However, it is unknown whether this conclusion extends to the transmitted viral subpopulation because it is technically difficult to sequence DENV genomes in mosquito saliva. Here, we achieved DENV full-genome sequencing by pooling saliva samples collected non-sacrificially from 49 to 163 individual mosquitoes previously infected with one of two DENV-1 genotypes. We compared the transmitted viral subpopulations found in the pooled saliva samples collected in time series with the input viral population present in the infectious blood meal. In all pooled saliva samples examined, the full-genome consensus sequence of the input viral population was unchanged. Although the pooling strategy prevents analysis of individual saliva samples, our results demonstrate the lack of strong convergent positive selection during a single round of DENV transmission by . This finding reinforces the idea that genetic drift and purifying selection are the dominant evolutionary forces shaping within-host DENV genetic diversity during transmission by mosquitoes.
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http://dx.doi.org/10.1093/ve/vex031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5782851PMC
July 2017

Seroprevalence of Dengue and Chikungunya Virus Antibodies, French Polynesia, 2014-2015.

Emerg Infect Dis 2018 03;24(3):558-561

We investigated dengue and chikungunya virus antibody seroprevalence in French Polynesia during 2014-2015. Dengue virus seroprevalence was ≈60% among schoolchildren and >83% among the general population; chikungunya virus seroprevalence was <3% before and 76% after Zika virus emergence (2013). Dengue virus herd immunity may affect Zika virus infection and pathogenesis.
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http://dx.doi.org/10.3201/eid2403.171149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5823337PMC
March 2018

Zika virus evolution on the edges of the Pacific ocean.

Emerg Microbes Infect 2017 12 13;6(12):e111. Epub 2017 Dec 13.

Institut Pasteur, Environment and Infectious Risks Unit, Laboratory for Urgent Response to Biological Threats, 75 724 Paris, France.

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http://dx.doi.org/10.1038/emi.2017.102DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5750458PMC
December 2017

Revising rates of asymptomatic Zika virus infection based on sentinel surveillance data from French Overseas Territories.

Int J Infect Dis 2017 Dec 1;65:116-118. Epub 2017 Dec 1.

Direction of Health, Papeete, French Polynesia.

French Polynesia and the French Territories of the Americas (FTAs) have experienced outbreaks of Zika virus (ZIKV) infection. These territories used similar sentinel syndromic surveillance to follow the epidemics. However, the surveillance system only takes into account consulting patients diagnosed with ZIKV disease, while non-consulting cases, as well as asymptomatic cases, are not taken into account. In the French territories under study, the ratio of consulting to non-consulting patients was found to likely be as low as 1/3 to 1/4, and rough estimates of the ZIKV asymptomatic infections indicated a lower rate than previously reported (i.e., not more than half).
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http://dx.doi.org/10.1016/j.ijid.2017.10.009DOI Listing
December 2017

Ross River Virus Seroprevalence, French Polynesia, 2014-2015.

Emerg Infect Dis 2017 10;23(10):1751-1753

Ross River virus (RRV), spread by Aedes and Culex mosquitoes, is the most commonly transmitted arbovirus in Australia. A serosurvey of blood donors in French Polynesia during 2011-2013 suggested that RRV circulated without being detected. We report RRV circulation in French Polynesia based on further screening of blood samples collected during 2014-2015.
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http://dx.doi.org/10.3201/eid2310.170583DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5621548PMC
October 2017

Dengue-1 virus and vector competence of Aedes aegypti (Diptera: Culicidae) populations from New Caledonia.

Parasit Vectors 2017 Aug 9;10(1):381. Epub 2017 Aug 9.

Institut Pasteur de Nouvelle-Calédonie, URE-Dengue et autres Arboviroses, Réseau International Institut Pasteur, Nouméa, New Caledonia.

Background: Dengue virus (DENV) is the arbovirus with the highest incidence in New Caledonia and in the South Pacific region. In 2012-2014, a major DENV-1 outbreak occurred in New Caledonia. The only known vector of DENV in New Caledonia is Aedes aegypti but no study has yet evaluated the competence of New Caledonia Ae. aegypti populations to transmit DENV. This study compared the ability of field-collected Ae. aegypti from different locations in New Caledonia to transmit the DENV-1 responsible for the 2012-2014 outbreak. This study also aimed to compare the New Caledonia results with the vector competence of Ae. aegypti from French Polynesia as these two French countries have close links, including arbovirus circulation.

Methods: Three wild Ae. aegypti populations were collected in New Caledonia and one in French Polynesia. Female mosquitoes were orally exposed to DENV-1 (10 FFU/ml). Mosquito bodies (thorax and abdomen), heads and saliva were analyzed to measure infection, dissemination, transmission rates and transmission efficiency, at 7, 14 and 21 days post-infection (dpi), respectively.

Results: DENV-1 infection rates were heterogeneous, but dissemination rates were high and homogenous among the three Ae. aegypti populations from New Caledonia. Despite this high DENV-1 dissemination rate, the transmission rate, and therefore the transmission efficiency, observed were low. Aedes aegypti population from New Caledonia was less susceptible to infection and had lower ability to transmit DENV-1 than Ae. aegypti populations from French Polynesia.

Conclusion: This study suggests that even if susceptible to infection, the New Caledonian Ae. aegypti populations were moderately competent vectors for DENV-1 strain from the 2012-2014 outbreak. These results strongly suggest that other factors might have contributed to the spread of this DENV-1 strain in New Caledonia and in the Pacific region.
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http://dx.doi.org/10.1186/s13071-017-2319-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5551013PMC
August 2017

Acquittal of Culex quinquefasciatus in transmitting Zika virus during the French Polynesian outbreak.

Acta Trop 2017 Sep 3;173:200-201. Epub 2017 May 3.

Institut Louis Malardé, BP 30, 98713 Papeete, Tahiti, French Polynesia. Electronic address:

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http://dx.doi.org/10.1016/j.actatropica.2017.04.036DOI Listing
September 2017

High risk of dengue type 2 outbreak in French Polynesia, 2017.

Euro Surveill 2017 Apr;22(14)

Unit of Emerging Infectious Diseases, Institut Louis Malardé, Papeete, Tahiti, French Polynesia.

In French Polynesia, the four serotypes of dengue virus (DENV-1 to -4) have caused 14 epidemics since the mid-1940s. From the end of 2016, an increasing number of Pacific Island Countries and Territories have reported DENV-2 outbreaks and in February 2017, DENV-2 infection was detected in French Polynesia in three travellers from Vanuatu. As DENV-2 has not been circulating in French Polynesia since December 2000, there is high risk for an outbreak to occur.
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http://dx.doi.org/10.2807/1560-7917.ES.2017.22.14.30505DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5388125PMC
April 2017

Real-Time Assessment of Health-Care Requirements During the Zika Virus Epidemic in Martinique.

Am J Epidemiol 2017 Nov;186(10):1194-1203

The spread of Zika virus in the Americas has been associated with a surge in Guillain-Barré syndrome (GBS) cases. Given the severity of GBS, territories affected by Zika virus need to plan health-care resources to manage GBS patients. To inform such planning in Martinique, we analyzed Zika virus surveillance and GBS data from Martinique in real time with a modeling framework that captured dynamics of the Zika virus epidemic, the risk of GBS in Zika virus-infected persons, and the clinical management of GBS cases. We compared our estimates with those from the 2013-2014 Zika virus epidemic in French Polynesia. We were able to predict just a few weeks into the epidemic that, due to lower transmission potential and lower probability of developing GBS following infection in Martinique, the total number of GBS cases in Martinique would be substantially lower than suggested by simple extrapolations from French Polynesia. We correctly predicted that 8 intensive-care beds and 7 ventilators would be sufficient to treat GBS cases. This study showcased the contribution of modeling to inform local health-care planning during an outbreak. Timely studies that estimate the proportion of infected persons that seek care are needed to improve the predictive power of such approaches.
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http://dx.doi.org/10.1093/aje/kwx008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5860153PMC
November 2017

New evidence for endemic circulation of Ross River virus in the Pacific Islands and the potential for emergence.

Int J Infect Dis 2017 Apr 8;57:73-76. Epub 2017 Feb 8.

The University of Adelaide, Adelaide, South Australia, Australia.

Objectives: An epidemic of Ross River virus (RRV) occurred in the South Pacific in 1979-1980, but RRV has not been thought to occur endemically outside Australia and Papua New Guinea. A seroprevalence study was conducted to determine whether RRV has circulated in American Samoa since 1980.

Methods: RRV ELISA IgG was performed on 200 serum samples collected in American Samoa in 2010; seroneutralization tests were performed on 60 representative samples.

Results: Of 196 available ELISA IgG results, 145 (74%, 95% confidence interval 67-80%) were seropositive. Of the 60 samples subjected to seroneutralization testing, none of the 15 ELISA IgG-negative and 16 of the 45 ELISA IgG-positive samples neutralized RRV. ELISA IgG seroprevalence was higher in persons born before/during the 1979-1980 RRV outbreak (78.3%), but was also high (63.0%) in people born after the outbreak who had lived their entire lives in American Samoa.

Conclusions: This study provides serological evidence that RRV circulation is likely to have occurred in American Samoa after 1980. Considering there are no marsupials in American Samoa, this finding implies that other species are capable of acting as reservoir hosts and indicates the potential for RRV to circulate in a much wider area than those currently recognized.
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http://dx.doi.org/10.1016/j.ijid.2017.01.041DOI Listing
April 2017

Zika rash and increased risk of congenital brain abnormalities.

Lancet 2017 01 13;389(10065):151-152. Epub 2017 Jan 13.

Service de réanimation néonatale, Centre Hospitalier of French Polynesia, Pirae, French Polynesia.

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http://dx.doi.org/10.1016/S0140-6736(17)30014-4DOI Listing
January 2017

Zika Virus Seroprevalence, French Polynesia, 2014-2015.

Emerg Infect Dis 2017 04 15;23(4):669-672. Epub 2017 Apr 15.

During 2013-2014, French Polynesia experienced an outbreak of Zika virus infection. Serosurveys conducted at the end of the outbreak and 18 months later showed lower than expected disease prevalence rates (49%) and asymptomatic:symptomatic case ratios (1:1) in the general population but significantly different prevalence rates (66%) and asymptomatic:symptomatic ratios (1:2) in schoolchildren.
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http://dx.doi.org/10.3201/eid2304.161549DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5367400PMC
April 2017

Axl Mediates ZIKA Virus Entry in Human Glial Cells and Modulates Innate Immune Responses.

Cell Rep 2017 01;18(2):324-333

INSERM U944, CNRS 7212 Laboratoire de Pathologie et Virologie Moléculaire, Hôpital Saint-Louis, 1 avenue Claude Vellefaux, 75010 Paris, France; Institut Universitaire d'Hématologie, Hôpital Saint-Louis, 1 avenue Claude Vellefaux, 75010 Paris, France; University Paris Diderot, Sorbonne Paris Cité, Hôpital St. Louis, 1 avenue Claude Vellefaux, 75475 Paris Cedex 10, France. Electronic address:

ZIKA virus (ZIKV) is an emerging pathogen responsible for neurological disorders and congenital microcephaly. However, the molecular basis for ZIKV neurotropism remains poorly understood. Here, we show that Axl is expressed in human microglia and astrocytes in the developing brain and that it mediates ZIKV infection of glial cells. Axl-mediated ZIKV entry requires the Axl ligand Gas6, which bridges ZIKV particles to glial cells. Following binding, ZIKV is internalized through clathrin-mediated endocytosis and traffics to Rab5+ endosomes to establish productive infection. During entry, the ZIKV/Gas6 complex activates Axl kinase activity, which downmodulates interferon signaling and facilitates infection. ZIKV infection of human glial cells is inhibited by MYD1, an engineered Axl decoy receptor, and by the Axl kinase inhibitor R428. Our results highlight the dual role of Axl during ZIKV infection of glial cells: promoting viral entry and modulating innate immune responses. Therefore, inhibiting Axl function may represent a potential target for future antiviral therapies.
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http://dx.doi.org/10.1016/j.celrep.2016.12.045DOI Listing
January 2017