Dengue and Dengue Haemorrhagic Fever in French Polynesia-Current Situation

All four dengue virus serotypes have occurred in French Polynesia. The first epidemic of dengue on Tahiti island of known serotype (dengue 1) occurred in 1944 as part of the Pacific-wide spread of the disease during World War II. The next outbreak of dengue took place in 1964 and was the result of the introduction of dengue 3 virus. With the increase in air travel by humans, dengue has occurred as successive epidemics, especially between 1969 and 1979 with each epidemic involving a different serotype. Each time, the epidemic serotype replaced the unique endemic serotype that had been transmitted during the preceeding interepidemic period: dengue type 3 in 1969, dengue 2 in 1971, dengue 1 in 1975-1976 and dengue 4 in 1979. With the exception of the dengue 2 epidemic, during which severe haemorrhagic cases and several deaths were observed on Tahiti on 1971, cases of dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS) were not common. Following a long inter-epidemic period involving a low transmission of dengue 4, two back-to-back epidemics of dengue 1 and dengue 3 took place during 1988-1989. Of great interest was the occurrence of DHF/DSS in the latter epidemic (11 fatalities) while mildness characterized the former. Surveillance of both epidemics involved clinically and laboratory-based systems. Public health control measures were instituted. These viruses were throughoutly spread in the Pacific region with varying degrees of disease severity. Molecular epidemiology studies provided new information on geographic distribution, origin, evolution and strain variation among dengue viruses

Human T-cell Leukemia Virus Type 1 Molecular Variants, Vanuatu, Melanesia

Four of 391 Ni-Vanuatu women were infected with variants of human T-cell leukemia virus type 1 (HTLV-1) Melanesian subtype C. These strains had env nucleotide sequences ≈99% similar to each other and diverging from the main molecular subtypes of HTLV-1 by 6% to 9%. These strains were likely introduced during ancient human population movements in Melanesia

Dengue Virus Type 3, Brazil, 2002

An explosive epidemic of DENV-3 in 2002 was the most severe dengue epidemic reported in Brazil since dengue viruses were introduced

Molecular epidemiology of dengue 3 viruses and genetic relatedness among dengue 3 strains isolated from patients with mild or severe form of dengue fever in French Polynesia

International audienceThe nucleotide sequences of a short fragment of the envelope protein gene encoding amino acids 25 to 89 of 27 dengue 3 viruses were determined by direct sequencing of PCR-amplified products, and the viruses were compared regarding their time of isolation and geographic distribution. Four distinct genotypic groups were discerned at 6% divergence between nucleotide sequences. The first group contained isolates from the South Pacific (1988 to 1992), Singapore (1973) and Indonesia (1973 to 1991). The second group comprised viruses from Asia (1956 to 1989) including the reference strain H-87. The third was composed of one isolate from Thailand (1971), and the fourth included the early strains from French Polynesia (1964 to 1969) and from Puerto Rico (1963). Furthermore, the difference between early and recent strains from the South Pacific was as high as 12.3%. This observation suggests that the recent epidemics in the South Pacific were probably the consequence of the spread of a new variant that emerged from New Caledonia. However, relatedness between nucleotide sequence and disease severity, or between strains from epidemics with mild disease (New Caledonia) and strains from epidemics with severe disease (French Polynesia) could not be demonstrated

Variation in oral susceptibility to dengue type 2 virus of populations of Aedes aegypti from the islands of Tahiti and Moorea, French Polynesia.

International audienceTwenty three samples of Aedes aegypti populations from the islands of Tahiti and Moorea (French Polynesia) were tested for their oral susceptibility to dengue type 2 virus. The high infection rates obtained suggest that the artificial feeding protocol used was more efficient than those previously described. Statistical analysis of the results allowed us to define two distinct geographic areas on Tahiti with respect to the susceptibility of Ae. aegypti: the east coast, with homogeneous infection rates, and the west coast, with heterogeneous infection rates. No geographic differences could be demonstrated on Moorea. The possible mechanisms of this phenomenon are discussed in connection with recent findings on the variability of susceptibility of Ae. aegypti to insecticides

A Novel Human T-lymphotropic Virus Type 1c Molecular Variant in an Indigenous Individual from New Caledonia, Melanesia

International audienceBackground: Human T-Lymphotropic Virus type 1 (HTLV-1) is endemic among people of Melanesian descent in Papua New Guinea, Solomon Islands and Vanuatu, and in Indigenous populations from Central Australia. Molecular studies revealed that these Australo-Melanesian strains constitute the highly divergent HTLV-1c subtype. New Caledonia is a French overseas territory located in the Southwest Pacific Ocean. HTLV-1 situation is poorly documented in New Caledonia and the molecular epidemiology of HTLV-1 infection remains unknown. Objectives: Studying 500 older adults Melanesian natives from New Caledonia, we aim to evaluate the HTLV-1 seroprevalence and to molecularly characterize HTLV-1 proviral strains. Study design: Plasma from 262 men and 238 females (age range: 60–96 years old, mean age: 70.5) were screened for anti-HTLV-1 antibodies by particle agglutination (PA) and indirect immunofluorescence assay (IFA). Serological confirmation was obtained using Western blot assay. DNAs were extracted from peripheral blood buffy coat of HTLV-1 seropositive individuals, and subjected to four series of PCR (LTR-gag; pro-pol; pol-env and tax-LTR). Primers were designed from highly common conserved regions of the major HTLV-1 subtypes to characterize the entire HTLV-1 proviral genome. Results: Among 500 samples, 3 were PA and IFA positive. The overall seroprevalence was 0.6%. The DNA sample from 1 New Caledonian woman (NCP201) was found positive by PCR and the complete HTLV-1 proviral genome (9,033-bp) was obtained. The full-length HTLV-1 genomic sequence from a native woman from Vanuatu (EM5), obtained in the frame of our previous studies, was also characterized. Both sequences belonged to the HTLV-1c Australo-Melanesian subtype. The NCP201 strain exhibited 0.3% nucleotide divergence with the EM5 strain from Vanuatu. Furthermore, divergence reached 1.1% to 2.9% with the Solomon and Australian sequences respectively. Phylogenetic analyses on a 522-bp-long fragment of the gp21-env gene showed the existence of two major clades. The first is composed of strains from Papua New Guinea; the second includes strains from all neighboring archipelagos (Solomon, Vanuatu, New Caledonia), and Australia. Interestingly, this second clade itself is divided into two sub-clades: strains from Australia on one hand, and strains from Solomon Islands, Vanuatu and New Caledonia on the other hand. Conclusions: The HTLV-1 seroprevalence (0.6%) in the studied adult population from New Caledonia appears to be low. This seroprevalence is quite similar to the situation observed in Vanuatu and Solomon Islands. However it is very different to the one encountered in Central Australia. Taken together, these results demonstrated that Australo-Melanesia is endemic for HTLV-1 infection with a high diversity of HTLV-1c strains and a clear geographic clustering according to the island of origin of HTLV-1 infected persons

Human T lymphotropic virus type 1 subtype C melanesian genetic variants of the Vanuatu Archipelago and Solomon Islands share a common ancestor.

International audienceBACKGROUND: Melanesia is endemic for human T lymphotropic virus type 1 (HTLV-1) subtype C. In 2005, we identified 4 infected women from Ambae Island, Vanuatu. Subsequently, 4247 Ni-Vanuatu originating from 18 islands were enrolled to define HTLV-1 epidemiological determinants and to characterize the viral strains molecularly. METHODS: Plasma from 1074 males and 3173 females were screened for HTLV-1/2 antibodies by particle agglutination (PA) and an immunofluorescence assay (IFA). Positive and/or borderline samples were then tested by a Western blot (WB) confirmatory assay. DNAs were amplified to obtain a 522-bp env gene fragment. Phylogenetic and molecular-clock analyses were performed. RESULTS: Of 4247 samples, 762 were positive and/or borderline by IFA/PA, and 26 of them were confirmed to be HTLV-1 positive by WB. The overall HTLV-1 seroprevalence was 0.62%. Viral transmission was found within families of infected index case patients. A geographic heterogeneity of HTLV-1 seroprevalence was observed among the islands. All 41 of the new env sequences belonged to HTLV-1 subtype C. Phylogenetic and molecular-clock analyses suggested that Ni-Vanuatu and Solomon Islander strains emerged from a common ancestor ~10,000 years ago. CONCLUSION: The Vanuatu archipelago is endemic for HTLV-1 with a diversity of subtype C variants. These strains were probably introduced into Vanuatu during ancient migration of the original settlers a few thousand years ago