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

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.

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

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.

Zika Virus Seroprevalence, French Polynesia, 2014-2015.

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.

Guillain-Barré Syndrome outbreak associated with Zika virus infection in French Polynesia: a case-control study.

BACKGROUND: Between October, 2013, and April, 2014, French Polynesia experienced the largest Zika virus outbreak ever described at that time. During the same period, an increase in Guillain-Barré syndrome was reported, suggesting a possible association between Zika virus and Guillain-Barré syndrome. We aimed to assess the role of Zika virus and dengue virus infection in developing Guillain-Barré syndrome. METHODS: In this case-control study, cases were patients with Guillain-Barré syndrome diagnosed at the Centre Hospitalier de Polynésie Française (Papeete, Tahiti, French Polynesia) during the outbreak period. Controls were age-matched, sex-matched, and residence-matched patients who presented at the hospital with a non-febrile illness (control group 1; n=98) and age-matched patients with acute Zika virus disease and no neurological symptoms (control group 2; n=70). Virological investigations included RT-PCR for Zika virus, and both microsphere immunofluorescent and seroneutralisation assays for Zika virus and dengue virus. Anti-glycolipid reactivity was studied in patients with Guillain-Barré syndrome using both ELISA and combinatorial microarrays. FINDINGS: 42 patients were diagnosed with Guillain-Barré syndrome during the study period. 41 (98%) patients with Guillain-Barré syndrome had anti-Zika virus IgM or IgG, and all (100%) had neutralising antibodies against Zika virus compared with 54 (56%) of 98 in control group 1 (p<0.0001). 39 (93%) patients with Guillain-Barré syndrome had Zika virus IgM and 37 (88%) had experienced a transient illness in a median of 6 days (IQR 4-10) before the onset of neurological symptoms, suggesting recent Zika virus infection. Patients with Guillain-Barré syndrome had electrophysiological findings compatible with acute motor axonal neuropathy (AMAN) type, and had rapid evolution of disease (median duration of the installation and plateau phases was 6 [IQR 4-9] and 4 days [3-10], respectively). 12 (29%) patients required respiratory assistance. No patients died. Anti-glycolipid antibody activity was found in 13 (31%) patients, and notably against GA1 in eight (19%) patients, by ELISA and 19 (46%) of 41 by glycoarray at admission. The typical AMAN-associated anti-ganglioside antibodies were rarely present. Past dengue virus history did not differ significantly between patients with Guillain-Barré syndrome and those in the two control groups (95%, 89%, and 83%, respectively). INTERPRETATION: This is the first study providing evidence for Zika virus infection causing Guillain-Barré syndrome. Because Zika virus is spreading rapidly across the Americas, at risk countries need to prepare for adequate intensive care beds capacity to manage patients with Guillain-Barré syndrome. FUNDING: Labex Integrative Biology of Emerging Infectious Diseases, EU 7th framework program PREDEMICS. and Wellcome Trust.

Potential sexual transmission of Zika virus.

In December 2013, during a Zika virus (ZIKV) outbreak in French Polynesia, a patient in Tahiti sought treatment for hematospermia, and ZIKV was isolated from his semen. ZIKV transmission by sexual intercourse has been previously suspected. This observation supports the possibility that ZIKV could be transmitted sexually.

Dengue virus type 3, South Pacific Islands, 2013.

After an 18-year absence, dengue virus serotype 3 reemerged in the South Pacific Islands in 2013. Outbreaks in western (Solomon Islands) and eastern (French Polynesia) regions were caused by different genotypes. This finding suggested that immunity against dengue virus serotype, rather than virus genotype, was the principal determinant of reemergence.

Epidemiological and molecular features of dengue virus type-1 in New Caledonia, South Pacific, 2001-2013.

BACKGROUND: The epidemiology of dengue in the South Pacific has been characterized by transmission of a single dominant serotype for 3-5 years, with subsequent replacement by another serotype. From 2001 to 2008 only DENV-1 was reported in the Pacific. In 2008, DENV-4 emerged and quickly displaced DENV-1 in the Pacific, except in New Caledonia (NC) where DENV-1 and DENV-4 co-circulated in 2008-2009. During 2012-2013, another DENV-1 outbreak occurred in NC, the third DENV-1 outbreak in a decade. Given that dengue is a serotype-specific immunizing infection, the recurrent outbreaks of a single serotype within a 10-year period was unexpected. FINDINGS: This study aimed to inform this phenomenon by examining the phylogenetic characteristics of the DENV-1 viruses in NC and other Pacific islands between 2001 and 2013. As a result, we have demonstrated that NC experienced introductions of viruses from both the Pacific (genotype IV) and South-east Asia (genotype I). Moreover, whereas genotype IV and I were co-circulating at the beginning of 2012, we observed that from the second half of 2012, i.e. during the major DENV-1 outbreak, all analyzed viruses were genotype I suggesting that a genotype switch occurred. CONCLUSIONS: Repeated outbreaks of the same dengue serotype, as observed in NC, is uncommon in the Pacific islands. Why the earlier DENV-1 outbreaks did not induce sufficient herd immunity is unclear, and likely multifactorial, but the robust vector control program may have played a role by limiting transmission and thus maintaining a large susceptible pool in the population.

Dengue-3 virus genomic differences that correlate with in vitro phenotype on a human cell line but not with disease severity.

We compared the full genome sequence of nine clinical isolates of dengue virus obtained during an epidemic of dengue-3 in French Polynesia in 1989, from patients with various presentations of disease. The isolates, all belonging to Genotype I, had 25 amino acid substitutions. There was no association with disease severity. When cultured in the K562 human erythroleukemia cell line, the isolates induced a range of cell growth inhibitions that was not associated with the degree of disease severity. By contrast, some substitutions--charge changes in NS1 and NS5, side-chain differences in NS1, loss of the E-153 potential glycosylation site, and 11 nucleotide insertions in the 3'UTR--that have been suggested to result in an increase or attenuation of dengue infection, appeared to be associated with the level of inhibition. These data represent the first documented study of an association between differences in the full dengue-3 genome of clinical isolates and the in vitro phenotype of these isolates on a human cell line.

Detection of Zika virus in saliva.

BACKGROUND: During the largest Zika virus (ZIKV) outbreak ever reported that occurred from October 2013 to March 2014 in French Polynesia, we observed that several patients presenting the symptoms of acute phase Zika fever were tested negative in blood by ZIKV real-time PCR (RT-PCR). OBJECTIVES: As we have previously detected ZIKV RNA in the saliva of a young child, we investigated the use of saliva as an alternative sample for routine ZIKV RNA detection. STUDY DESIGN: Over a 6 month period, 1,067 samples collected from 855 patients presenting symptoms of Zika fever (saliva only, blood only or both samples) were tested using a specific ZIKV RT-PCR. A medical questionnaire was available for most of the patients. RESULTS: ZIKV was more frequently detected in saliva compared to blood. For the 182 patients with both samples collected, tests were positive for 35 (19.2%) in saliva while negative in blood and tests were positive for 16 (8.8%) in blood while negative in saliva; the difference in mean days after symptoms onset and the percentage of the main symptoms of Zika fever for patients only positive in saliva or in blood was not significant. CONCLUSION: The use of saliva sample increased the rate of molecular detection of ZIKV at the acute phase of the disease but did not enlarge the window of detection of ZIKV RNA. Saliva was of particular interest when blood was difficult to collect (children and neonates especially).

Seroprevalence of arboviruses among blood donors in French Polynesia, 2011-2013.

OBJECTIVES: French Polynesia is a high epidemic/endemic area for arthropod-borne viruses (arboviruses). We recently reported the silent circulation of Ross River virus and absence of active transmission of chikungunya virus (CHIKV) among blood donors sampled before the emergence of Zika virus (ZIKV) and CHIKV in French Polynesia. In this study, the prevalence of the four serotypes of dengue virus (DENV) and the occurrence of circulation of other arboviruses were investigated in blood donors in French Polynesia. METHODS: Serum samples from 593 blood donors collected between July 2011 and October 2013 were tested by ELISA for the presence of immunoglobulin G antibodies against each of the four DENV serotypes, ZIKV, Japanese encephalitis virus (JEV), and West Nile virus (WNV). RESULTS: It was found that 80.3%, 0.8%, 1.3%, and 1.5% of blood donors were seropositive for at least one DENV serotype, ZIKV, JEV, and WNV, respectively. CONCLUSIONS: These results corroborate the expected high transmission of DENV and conversely suggest that no active circulation of ZIKV, JEV, and WNV occurred in French Polynesia before 2011. Information provided by this study may be useful for public health authorities to improve surveillance and implement strategies to prevent the transmission of arboviruses.

Silent Circulation of Ross River Virus in French Polynesia.

OBJECTIVES: Ross River is an emerging mosquito-borne disease in the Western Pacific. Ross River virus (RRV) circulation has been sporadically reported in some Pacific Island Countries and Territories but never in French Polynesia. To determine if RRV has circulated locally among the French Polynesian population, we conducted a seroprevalence study on blood donors. METHODS: Sera of 593 blood donors were collected from July 2011 to October 2013 and tested by ELISA for the presence of RRV-specific Immunoglobulin G (IgG) antibodies. RESULTS: A total of 204 (34.40%) blood donors were found seropositive for RRV. Among the 132 blood donors that were born in French Polynesia and had never travelled abroad, 56 (42.42%) had RRV-specific IgGs. DISCUSSION: Our results support the existence of autochthonous RRV transmission and suggest that this pathogen has silently circulated in French Polynesia. These findings raise the question of possible undetected circulation of RRV in other Pacific Island Countries and Territories.

Comparison of dengue-1 virus envelope glycoprotein gene sequences from French Polynesia.

Dengue (DEN) is the leading arboviral infection of humans, with 100 million cases annually in the tropical areas of the world. The recent severe DEN-1 epidemic in French Polynesia in 2001, with an incidence rate of 16% and more than 45% of the cases with dengue hemorrhagic fever/dengue shock syndrome among 1,400 hospitalized children and eight fatalities, led us to study this new circulating strain. The entire envelope (E) gene of two French Polynesian DEN-1 virus isolates from the two epidemics of 1988-1989 (FP89) and 2001 (FP01) were sequenced and compared with 29 published DEN-1 virus E gene sequences. Phylogenetic relationships showed that the FP89 strain belonged to genotype V and the FP01 strain to genotype IV based on studies on the same region of DEN-1 virus genome (1,485 nucleotides). The recent dengue epidemic in French Polynesia in 2001 was probably due to the introduction of a new DEN-1 virus from Southeast Asia, since the minimum nucleotide divergence was 3.3% with A88, the Indonesian strain isolated in 1988 in Jakarta.

Improvement of leptospirosis surveillance in remote Pacific islands using serum spotted on filter paper.

OBJECTIVES: Leptospirosis is a serious neglected disease in the Pacific. Because sensitive and specific laboratory tests are largely unavailable, the burden of disease and epidemiological data are often unreliable and do not allow informed disease prioritization and efficient control. We report the use of serum spotted on filter paper to improve the surveillance of leptospirosis in remote and resource-limited settings. METHODS: A total of 172 acute-phase serum samples collected from patients with suspected dengue at Yap State Hospital, Federated States of Micronesia, were spotted on filter paper and sent by regular mail to the Institut Louis Malardé, French Polynesia. Real-time PCR protocols for dengue and leptospirosis confirmation were performed on all specimens. RESULTS: A total of five leptospirosis infections were detected amongst the patients with suspected dengue. CONCLUSIONS: This study confirms the use of filter paper as a convenient tool to improve leptospirosis surveillance capacity in remote areas. New surveillance strategies, notably based on the regular use of this type of tool, are essential to more adequately describe the epidemiology and burden of neglected diseases.

Use of serum and blood samples on filter paper to improve the surveillance of Dengue in Pacific Island Countries.

BACKGROUND: In Pacific Island Countries (PICs) the epidemiology of dengue is characterized by long-term transmission of a single dengue virus (DENV) serotype. The emergence of a new serotype in one island country often indicates major outbreaks with this serotype will follow in other PICs. OBJECTIVES: Filter paper (FP) cards on which whole blood or serum from dengue suspected patients had been dried was evaluated as a method for transportation of this material by standard mail delivery throughout the Pacific. STUDY DESIGN: Twenty-two FP-dried whole blood samples collected from patients in New Caledonia and Wallis & Futuna Islands, during DENV-1 and DENV-4 transmission, and 76 FP-dried sera collected from patients in Yap State, Majuro (Republic of Marshall Islands), Tonga and Fiji, before and during outbreaks of DENV-2 in Yap State and DENV-4 in Majuro, were tested for the presence of DENV RNA, by serotype specific RT-PCR, at the Institut Louis Malardé in French Polynesia. RESULTS: The serotype of DENV could be determined, by a variety of RT-PCR procedures, in the FP-dried samples after more than three weeks of transport at ambient temperatures. In most cases, the sequencing of the envelope gene to genotype the viruses also was possible. CONCLUSIONS: The serotype and genotype of DENV can be determined from FP-dried serum or whole blood samples transported over thousands of kilometers at ambient, tropical, temperatures. This simple and low-cost approach to virus identification should be evaluated in isolated and resource poor settings for surveillance for a range of significant viral diseases.

Recent emergence of dengue virus serotype 4 in French Polynesia results from multiple introductions from other South Pacific Islands.

BACKGROUND: Infection by dengue virus (DENV) is a major public health concern in hundreds of tropical and subtropical countries. French Polynesia (FP) regularly experiences epidemics that initiate, or are consecutive to, DENV circulation in other South Pacific Island Countries (SPICs). In January 2009, after a decade of serotype 1 (DENV-1) circulation, the first cases of DENV-4 infection were reported in FP. Two months later a new epidemic emerged, occurring about 20 years after the previous circulation of DENV-4 in FP. In this study, we investigated the epidemiological and molecular characteristics of the introduction, spread and genetic microevolution of DENV-4 in FP. METHODOLOGY/PRINCIPAL FINDINGS: Epidemiological data suggested that recent transmission of DENV-4 in FP started in the Leeward Islands and this serotype quickly displaced DENV-1 throughout FP. Phylogenetic analyses of the nucleotide sequences of the envelope (E) gene of 64 DENV-4 strains collected in FP in the 1980s and in 2009-2010, and some additional strains from other SPICs showed that DENV-4 strains from the SPICs were distributed into genotypes IIa and IIb. Recent FP strains were distributed into two clusters, each comprising viruses from other but distinct SPICs, suggesting that emergence of DENV-4 in FP in 2009 resulted from multiple introductions. Otherwise, we observed that almost all strains collected in the SPICs in the 1980s exhibit an amino acid (aa) substitution V287I within domain I of the E protein, and all recent South Pacific strains exhibit a T365I substitution within domain III. CONCLUSIONS/SIGNIFICANCE: This study confirmed the cyclic re-emergence and displacement of DENV serotypes in FP. Otherwise, our results showed that specific aa substitutions on the E protein were present on all DENV-4 strains circulating in SPICs. These substitutions probably acquired and subsequently conserved could reflect a founder effect to be associated with epidemiological, geographical, eco-biological and social specificities in SPICs.

Dengue 1 diversity and microevolution, French Polynesia 2001-2006: connection with epidemiology and clinics.

BACKGROUND: Dengue fever (DF) is an emerging infectious disease in the tropics and subtropics. Determinants of DF epidemiology and factors involved in severe cases-dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS)-remain imperfectly characterized. Since 2000, serotype 1 (DENV-1) has predominated in the South Pacific. The aim of this study was (i) to determine the origin and (ii) to study the evolutionary relationships of DENV-1 viruses that have circulated in French Polynesia (FP) from the severe 2001 outbreak to the recent 2006 epidemic, and (iii) to analyse the viral intra-host genetic diversity according to clinical presentation. METHODOLOGY/PRINCIPAL FINDINGS: Sequences of 181 envelope gene and 12 complete polyproteins of DENV-1 viruses obtained from human sera in FP during the 2001-2006 period were generated. Phylogenetic analysis showed that all DENV-1 FP strains belonged to genotype IV-"South Pacific" and derived from a single introduction event from South-East Asia followed by a 6-year in situ evolution. Although the ratio of nonsynonymous/synonymous substitutions per site indicated strong negative selection, a mutation in the envelope glycoprotein (S222T) appeared in 2002 and was subsequently fixed. It was noted that genetic diversification was very significant during the 2002-2005 period of endemic DENV-1 circulation. For nine DF sera and eight DHF/DSS sera, approximately 40 clones/serum of partial envelope gene were sequenced. Importantly, analysis revealed that the intra-host genetic diversity was significantly lower in severe cases than in classical DF. CONCLUSIONS/SIGNIFICANCE: First, this study showed that DENV-1 epidemiology in FP was different from that described in other South-Pacific islands, characterized by a long sustained viral circulation and the absence of new viral introduction over a 6-year period. Second, a significant part of DENV-1 evolution was observed during the endemic period characterized by the rapid fixation of S222T in the envelope protein that may reflect genetic drift or adaptation to the mosquito vector. Third, for the first time, it is suggested that clinical outcome may be correlated with intra-host genetic diversity.