Zika virus is an arthropod-borne Flavivirus member of the Spondweni serocomplex, transmitted by Aedes mosquitoes. We report here the complete coding sequence of a Zika virus strain belonging to the Asian lineage, isolated from an infected patient returning from French Polynesia, an epidemic area in 2013/2014.

Dengue virus infection is the most frequent arthropod-borne infection affecting humans in the world. Our understanding of the pathophysiological events leading to mild or severe outcomes of the disease remains limited by the fact that viral target cells in the human body are poorly characterized. One of the most sensitive strategies for detecting cells supporting active replication of this positivestrand RNA virus is the search for the replicative intermediate, an antigenome of negative polarity, by RT-PCR. However, a phenomenon described as 'false priming' of the reverse transcriptase (RT) prevents strand-specific detection. The results of the current study showed that this event corresponds to cDNA synthesis that is independent of any primer addition. This property was general to all RNAs tested and was not associated with small free nucleic acids, such as tRNAs and microRNAs. Rather, it corresponded to initiation of cDNA synthesis from the 39 end of the RNA template, and a model is proposed in which the template RNA snaps back upon itself and creates a transient RNA primer suitable for the RT. Such a property would explain why many assays proposed for detection of a replicative intermediate are not specific, and may help in the development of a molecular biology protocol that could allow replication studies of RNA viruses of human interest, such as dengue virus, hepatitis C virus and enteroviruses. INTRODUCTIONDengue virus (DENV) is the most frequent mosquitoborne virus infection affecting humans in the world (http:// www.cdc.gov/ncidod.dvbid/dengue). It is a member of the genus Flavivirus, family Flaviviridae, and is represented by four viral serotypes, DENV1-4, that each year affect 50-100 million people in tropical and subtropical areas. Most D-ENV infections lead to a self-limiting febrile illness (dengue fever), but can also result in more severe diseases, such as dengue haemorrhagic fever and dengue shock syndrome. The mechanisms underlying the more severe outcomes of the infection are poorly understood.A significant number of host factors have been shown to be required for DENV propagation in insect and human cells (Sessions et al., 2009), but the crucial target cells for DENV remain controversial. DENV infection gives rise to a viraemic phase, and the presence of DENV proteins and nucleic acids has been detected in multiple organs (liver, spleen, kidney, lung and bone marrow;Jessie et al., 2004) and in circulating peripheral blood mononuclear cells, where monocytes, but not B or T cells, have been shown to be permissive to DENV infection (Blackley et al., 2007). However, this detection is not necessarily associated with active replication.DENV has a positive-sense RNA genome of approximately 11 kb encoding three structural and seven non-structural proteins, and is flanked by 59-and 39-untranslated regions (UTRs) that are partially complementary (Alvarez et al., 2005). A hallmark of active DENV replication, as with other members of the family Flaviviridae, is the presence of the negative-sense antig...

The development and validation of a one-step, single-tube, real-time accelerated reverse-transcription loop-mediated isothermal amplification (RT-LAMP) for the detection of the L RNA segment of Rift Valley fever virus (RVFV) are described. The assay was performed at a constant temperature (63°C), with a real-time follow-up using a LightCycler and a double-stranded-DNA-intercalating fluorochrome. The assay is highly sensitive and comparable to real-time RT-PCR, with a detection limit of ϳ10 RNA copies per assay. However, the RT-LAMP assay is much faster than traditional RT-PCR and generates results in <30 min for most diluted samples. The specificity of the primers was established using other, related arboviruses as well as viruscontaining and virus-free sera. The RT-LAMP assay reported here is thus a valuable tool for the rapid detection of RVFV in field diagnostic laboratories.

Dengue viruses (DENV) cause 50-100 million cases of acute febrile disease every year, including 500,000 reported cases of dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). Viral factors have been proposed to influence the severity of the disease, but markers of virulence have never been identified on DENV. Three DENV serotype-1 isolates from the 2007 epidemic in Cambodia that are derived from patients experiencing the various clinical forms of dengue were characterized both phenotypically and genetically. Phenotypic characteristics in vitro, based on replication kinetics in different cell lines and apoptosis response, grouped isolates from DF and DHF patients together, whereas the virus isolate from a DSS patient showed unique features: a lower level of replication in mammalian cells and extensive apoptosis in mosquito cells. Genomic comparison of viruses revealed six unique amino acid residues in the membrane, envelope, and in non-structural genes in the virus isolated from the DSS patient.

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