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- Quam, Mikkel, et al.
(författare)
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Dissecting the origin of the 2014 dengue outbreak in Japan
- 2015
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Ingår i: Tropical medicine & international health. - : Wiley-Blackwell. - 1360-2276 .- 1365-3156. ; 20:Suppl. 1, s. 408-408
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Endemic in at least 100 countries, dengue is currently regarded as world's most important mosquito borne viral disease. While most of the disease burden is limited to areas with tropical and sub-tropical climates, evidence suggests that temperate areas may be increasingly at risk as the geographic distribution of relevant vectors expands. Japan, a country with a temperate climate, reported the first major dengue outbreak in 2014. We examined the factors that may have facilitated the dengue outbreak in Tokyo during 2014.Methods: Multiple sequence alignment of the dengue virus 1 (DENV1) sequence from the 2014 dengue outbreak in Tokyo was carried out using a fast Fourier transformation method in MAFFT v6.940b. We collected the Japan National Tourism Organization’s data on inbound travelers between January and September 2014 from dengue endemic countries in Asia to Japan. Daily observations of temperature (minimum, maximum, and mean) and precipitation were obtained from the MIDAS dataset for Tokyo. We calculated the relative vectorial capacity (rVc) for Aedes vectors to quantify the dengue epidemic potential based on temperature dependent parameters, by applying a modified Ross-McDonald model.Findings: Tourist arrivals into Japan in 2014 coincided by 70% with its warm summer months suitable for dengue transmission, The phylogenetic similarity of DENV-1 isolated from the 2014 outbreak in Japan with viruses from China, Indonesia, Singapore, and Vietnam renders any of these four countries a likely source of importation. Several conducive climate factors converged preceding and during the time of the dengue outbreak in Tokyo, August until October 2014. Climate conditions, in particular mean temperature and precipitation, were favorable for the amplification of Aedes vectors. Furthermore, the ability for the vector to transmit dengue, as measured by the relative vectorial capacity, was highest at the time of the 2014 outbreak.Conclusions: Taking into account the travel volume into Japan, China appears the most probable source of dengue virus introduction that triggered Tokyo's outbreak. Despite Japan's temperate climate, dengue epidemic potential already exists. Under scenarios of changing climate and increasing regional travel, Japan will likely face more dengue outbreaks in the future.Acknowledgements: The study was financially supported by the European Union's Seventh Framework Programme- DengueTools (www.denguetools.net).Disclosure: Nothing to disclose.
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| 3. |
- Tissera, H, et al.
(författare)
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Enhanced dengue sentinel surveillance in Sri Lanka
- 2015
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Ingår i: Tropical medicine & international health. - [Tissera, H.; Palihawadana, P.; Amarasinghe, A.; Muthukuda, C.; Botheju, C.] Minist Hlth, Epidemiol it, Colombo, Sri Lanka. [Tissera, H.] Natl Dengue Control Unit, Colombo, Sri Lanka. [Gunasena, S.] Med Res Inst, Colombo, Sri Lanka. [da Silva, D.] Genentech Res Inst, Colombo, Sri Lanka. [Sessions, O.] Nanyang Technol Univ, Duke NUS Grad Med Sch, Singapore 639798, Singapore. [Leong, W. -Y.; Wilder-Smith, A.] Nanyang Technol Univ, Lee Kong Chian Sch Med, Singapore 639798, ngapore. [Lohr, W.; Byass, P.; Wilder-Smith, A.] Umea Univ, Umea, Sweden. [Gubler, D.] Duke NUS Grad Med Sch, Colombo, Sri Lanka.. - 1360-2276 .- 1365-3156. ; 20:Suppl. 1, s. 133-133
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Dengue poses a significant socioeconomic and disease burden in Sri Lanka, where the geographic spread, incidence and severity of disease has been increasing since the first dengue hemorrhagic fever (DHF) epidemic occurred in 1989. Periodic epidemics have become progressively larger, peaking in 2012 with 44 456 cases. Passive surveillance was established nationwide more than a decade ago but dengue notifications have been based on clinical diagnosis, with infrequent laboratory confirmation. To obtain more accurate data on the disease burden, a laboratory-based enhanced sentinel surveillance system was established in Colombo Municipality, the area with the highest dengue incidence. Here we describe the study design and the results of the first 2 years (2012–2014).Methods: Three government hospitals and two outpatient clinics in Colombo District were selected for the sentinel surveillance. All patients presenting with undifferentiated fever were enrolled, if consent given, capped at a maximum of 60 patients per week. Acute blood samples were taken from all enrolled subjects and tested by dengue-specific PCR, and NS1, and IgM – ELISA at the time of first presentation. A sub-set of 536 samples was sent to Duke-NUS Singapore for quality assurance, virus isolation and serotyping.Results: Between 1 April, 2012 and 31 March, 2014, 3127 patients were enrolled, 964 (30.9%) as outpatients and 2160 (69.1%) as inpatients. The mean age was 22.3 years (SD = 17.5) and the time of first presentation was at day 4 of illness. For inpatients, 1687 (78.1%) of all febrile cases had laboratory-confirmed dengue. For outpatients, the proportion of confirmed dengue was 237 (24.6%). The mean duration of hospitalization was 4.1 days (SD = 1.85). The proportion of DHF in lab-confirmed hospitalized dengue cases was 22.1% and 4 patients (0.21%) died. Serotypes 1 and 4 were the only viruses detected in this sample (serotype 1: 85%; serotype 4: 15%). The clinicians’ diagnosis for dengue at time of first presentation had a sensitivity of 92% and specificity of 23%.Conclusions: Dengue infection was responsible for a high proportion of febrile illnesses during 2012–2014, with serotypes 1 and 4 circulating. A significant proportion (22%) of hospitalized dengue cases developed DHF, but the case fatality rate was low. Clinicians’ judgment was associated with good sensitivity, but to enhance specificity it is important to add laboratory confirmation of dengue.Disclosure: This research was funded by the European Commission under the 7th Framework and conducted by DengueTools partners (www.denguetools.net).
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| 4. |
- Uehara, A, et al.
(författare)
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A hybridization-based enrichment strategy to increase the accuracy of next generation sequencing in phylogenetic analysis of dengue viruses in Sri Lanka
- 2015
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Ingår i: Tropical medicine & international health. - : Wiley-Blackwell. - 1360-2276 .- 1365-3156. ; 20:Suppl. 1, s. 120-120
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: Sri Lanka has experienced confirmed dengue outbreaks since the 1960s although severe dengue disease (DHF/DSS) didn’t appear until 1989. Since then, cyclical outbreaks associated with severe disease have occurred throughout the island. The most recent epidemic began in 2009 with the apparent introduction of a new genotype of DENV-1. To better understand the mechanisms underlying the persistence of this ongoing epidemic, a longitudinal study was conducted in hospitals in the Colombo district from April 2012 to March 2014. In order to glean as much information as possible about the viral genetics from this large cohort, we developed a novel Next Generation Sequencing (NGS) platform that can function without any a priori knowledge of the target dengue genome.Methods: The principle problem encountered when employing NGS directly on patient samples is the high ratio of host to viral RNA. To compensate for this, we developed a hybridization-based enrichment strategy consisting of DENV-specific 120nt, biotinylated oligodeoxynucleotides to capture DENV genomic material from an NGS library prepared directly from patient sera.Results: The strategy developed here allowed us to enrich DENV genomic material over 5000 fold relative to unenriched material. Full genome data and phylogenetic analysis indicate that the DENV-1 are predominantly genotype 1 although a smaller number of genotype 5 isolates was also identified.Conclusion: The platform developed for this study has the inherent ability to capture all four serotypes of DENV and can significantly increase the virus to host RNA ratio. The principle driver of the current dengue epidemic in Sri Lanka is the same DENV-1 genotype that has been in circulation since 2009.This research was funded by the Singapore Infectious Disease Initiative (SIDI/2013/012) and the European Union 7th Framework Programme through ‘DengueTools’. (www.dengue-tools.net).Disclosure: Nothing to disclose.
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| 5. |
- Wilder-Smith, Annelies, et al.
(författare)
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The 2012 dengue outbreak in Madeira : exploring the origins
- 2014
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Ingår i: Eurosurveillance. - 1025-496X .- 1560-7917. ; 19:8, s. 20718-
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Tidskriftsartikel (refereegranskat)abstract
- In 2012, Madeira reported its first major outbreak of dengue. To identify the origin of the imported dengue virus, we investigated the interconnectivity via air travel between dengue-endemic countries and Madeira, and compared available sequences against GenBank. There were 22,948 air travellers to Madeira in 2012, originating from twenty-nine dengue-endemic countries; 89.6% of these international travellers originated from Venezuela and Brazil. We developed an importation index that takes into account both travel volume and the extent of dengue incidence in the country of origin. Venezuela and Brazil had by far the highest importation indices compared with all other dengue-endemic countries. The importation index for Venezuela was twice as high as that for Brazil. When taking into account seasonality in the months preceding the onset of the Madeira outbreak, this index was even seven times higher for Venezuela than for Brazil during this time. Dengue sequencing shows that the virus responsible for the Madeira outbreak was most closely related to viruses circulating in Venezuela, Brazil and Columbia. Applying the importation index, Venezuela was identified as the most likely origin of importation of dengue virus via travellers to Madeira. We propose that the importation index is a new additional tool that can help to identify and anticipate the most probable country of origin for importation of dengue into currently non-endemic countries.
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