Dengue fever is the most widespread infectious disease of humans transmitted by Aedes mosquitoes. It is the leading cause of hospitalization and death in children in the Southeast Asia and western ...Pacific regions. We analyzed surveillance records from health centers in Vietnam collected between 2001-2012 to determine seasonal trends, develop risk maps and an incidence forecasting model.
The data were analyzed using a hierarchical spatial Bayesian model that approximates its posterior parameter distributions using the integrated Laplace approximation algorithm (INLA). Meteorological, altitude and land cover (LC) data were used as predictors. The data were grouped by province (n = 63) and month (n = 144) and divided into training (2001-2009) and validation (2010-2012) sets. Thirteen meteorological variables, 7 land cover data and altitude were considered as predictors. Only significant predictors were kept in the final multivariable model. Eleven dummy variables representing month were also fitted to account for seasonal effects. Spatial and temporal effects were accounted for using Besag-York-Mollie (BYM) and autoregressive (1) models. Their levels of significance were analyzed using deviance information criterion (DIC). The model was validated based on the Theil's coefficient which compared predicted and observed incidence estimated using the validation data. Dengue incidence predictions for 2010-2012 were also used to generate risk maps.
The mean monthly dengue incidence during the period was 6.94 cases (SD 14.49) per 100,000 people. Analyses on the temporal trends of the disease showed regular seasonal epidemics that were interrupted every 3 years (specifically in July 2004, July 2007 and September 2010) by major fluctuations in incidence. Monthly mean minimum temperature, rainfall, area under urban settlement/build-up areas and altitude were significant in the final model. Minimum temperature and rainfall had non-linear effects and lagging them by two months provided a better fitting model compared to using unlagged variables. Forecasts for the validation period closely mirrored the observed data and accurately captured the troughs and peaks of dengue incidence trajectories. A favorable Theil's coefficient of inequality of 0.22 was generated.
The study identified temperature, rainfall, altitude and area under urban settlement as being significant predictors of dengue incidence. The statistical model fitted the data well based on Theil's coefficient of inequality, and risk maps generated from its predictions identified most of the high-risk provinces throughout the country.
The complexity of mosquito-borne diseases poses a major challenge to global health efforts to mitigate their impact on people residing in sub-tropical and tropical regions, to travellers and deployed ...military personnel. To supplement drug- and vaccine-based disease control programmes, other strategies are urgently needed, including the direct control of disease vectors. Modern vector control research generally focuses on identifying novel active ingredients and/or innovative methods to reduce human-mosquito interactions. These efforts include the evaluation of spatial repellents, which are compounds capable of altering mosquito feeding behaviour without direct contact with the chemical source.
This project examined the impact of airborne transfluthrin from impregnated textile materials on two important malaria vectors, Anopheles dirus and Anopheles minimus. Repellency was measured by movement within taxis cages within a semi-field environment at the National Institute of Hygiene and Epidemiology in Hanoi, Vietnam. Knockdown and mortality were measured in adult mosquito bioassay cages. Metered-volume air samples were collected at a sub-set of points in the mosquito exposure trial.
Significant differences in knockdown/mortality were observed along a gradient from the exposure source with higher rates of knockdown/mortality at 2 m and 4 m when compared with the furthest distance (16 m). Knockdown/mortality was also greater at floor level and 1.5 m when compared to 3 m above the floor. Repellency was not significantly different except when comparing 2 m and 16 m taxis cages. Importantly, the two species reacted differently to transfluthrin, with An. minimus being more susceptible to knockdown and mortality. The measured concentrations of airborne transfluthrin ranged from below the limit of detection to 1.32 ng/L, however there were a limited number of evaluable samples complicating interpretation of these results.
This study, measuring repellency, knockdown and mortality in two malaria vectors in Vietnam demonstrates that both species are sensitive to airborne transfluthrin. The differences in magnitude of response between the two species requires further study before use in large-scale vector control programmes to delineate how spatial repellency would impact the development of insecticide resistance and the disruption of biting behaviour.
Bats are a major reservoir of zoonotic viruses, including coronaviruses. Since the emergence of SARS-CoV in 2002/2003 in Asia, important efforts have been made to describe the diversity of ...Coronaviridae circulating in bats worldwide, leading to the discovery of the precursors of epidemic and pandemic sarbecoviruses in horseshoe bats. We investigated the viral communities infecting horseshoe bats living in Northern Vietnam, and report here the first identification of sarbecoviruses in Rhinolophus thomasi and Rhinolophus siamensis bats. Phylogenetic characterization of seven strains of Vietnamese sarbecoviruses identified at least three clusters of viruses. Recombination and cross-species transmission between bats seemed to constitute major drivers of virus evolution. Vietnamese sarbecoviruses were mainly enteric, therefore constituting a risk of spillover for guano collectors or people visiting caves. To evaluate the zoonotic potential of these viruses, we analyzed in silico and in vitro the ability of their RBDs to bind to mammalian ACE2s and concluded that these viruses are likely restricted to their bat hosts. The workflow applied here to characterize the spillover potential of novel sarbecoviruses is of major interest for each time a new virus is discovered, in order to concentrate surveillance efforts on high-risk interfaces.
Contamination levels and distribution patterns of ten typical phthalic acid esters (PAEs) were investigated in various types of water samples collected from Hanoi metropolitan area in Vietnam. ...Concentrations of 10 PAEs in bottled water, tap water, lake water, and wastewater samples were measured in the ranges of 1640–15,700 ng/L (mean/median: 6400/5820 ng/L), 2100–18,000 ng/L (mean/median: 11,200/9270 ng/L), 19,600–127,000 ng/L (mean/median: 51,800/49,300 ng/L), and 20,700–405,000 ng/L (mean/median: 121,000/115,000 ng/L), respectively. Among PAEs, di-(2-ethylhexyl) phthalate (DEHP) accounted for a major proportion of total concentrations (45%) in wastewater, followed by diisobutyl phthalate (DiBP, 10.3%), and dibutyl phthalate (DBP, 9.53%). Concentrations of PAEs in wastewater decreased significantly with distance from the wastewater treatment plants (WWTPs). Concentrations of PAEs in surface water samples did not vary greatly between locations. PAEs were found in bottled water in the following order: DBP (22.4%), DiBP (22.3%), benzylbutyl phthalate (BzBP, 20.1%), and DEHP (15.5%). The estimated mean exposure doses of 10 PAEs through consumption of drinking water for adults and children in Vietnam were 254 and 256 ng/kg-bw/day, respectively.
Capsule: Highest concentrations of PAEs were measured in wastewater, followed by lake water, tap water, and bottled water.
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•Elevated concentrations of PAEs were measured in wastewater samples from Vietnam.•DEHP was a major compound found in tap water, lake water and wastewater samples.•DiBP and DBP were the dominant PAEs in bottled water.•PAE concentrations in drinking water and associated exposure doses were below the reference values.
The residue concentrations and congener profiles of polychlorinated dibenzo-
p
-dioxins/furans (PCDD/Fs) were examined in fly ash and bottom ash released from different thermal industrial processes ...in Vietnam. PCDD/F concentrations and toxic equivalents (TEQs) in the ash samples varied greatly and decreased in the following order: steel making > aluminum recycling > medical waste incinerator > boilers > municipal waste incinerator > tin production > brick production > coal-fired power plant. Both the precursor and de novo synthesis were estimated as possible formation mechanisms of dioxins in the ash, but the latter pathway was more prevalent. The highest emission factors were estimated for the ash released from some steel-making plants, aluminum-recycling facilities, and a medical waste incinerator. The emission factors of PCDD/Fs in ash released from some steel plants of this study were two to six times higher than the UNEP Toolkit default value. The annual emission amount of ash-bound dioxins produced by 15 facilities in our study was estimated to be 26.2 to 28.4 g TEQ year
−1
, which mainly contributed by 3 steel plants. Health risk related to the dioxin-containing ash was evaluated for workers at the studied facilities, indicating acceptable risk levels for almost all individuals. More comprehensive studies on the occurrence and impacts of dioxins in waste streams from incineration and industrial processes and receiving environments should be conducted, in order to promote effective waste management and health protection scheme for dioxins and related compounds in this rapidly industrializing country.
The use of 3D-printed Patient-Specific Instruments (PSI) has been investigated to enhance the postoperative functional results in total hip arthroplasty (THA) and has been recognized as an innovative ...approach for the optimal alignment of hip implant components. Point-of-care production is gradually becoming the norm for PSI manufacturing. The purpose of this article is to assess the accuracy and safety of PSI for total hip arthroplasty performed at the point-of-care in Vietnam.
34 THA cases were assessed in this prospective study. A template for the size and orientation of the implant and the design of the PSI was generated using data from preoperative 3D computed tomography (CT) scanning of the lower limb. The principal surgeon determined the implants' position and PSI design directly using the software. The PSI is then produced using a 3D-compatible resin printer in our manufacturing hospital. The PSI, consisting of an acetabulum and a femoral component placed press-fit on the bony surface, guided surgeons to precisely ream the acetabulum and cut the femoral neck according to the pre-planned plane. Postoperative CT scanning was obtained and superimposed onto the 3D model of the implant to evaluate the accuracy of the procedure by comparing the orientation values of the cup and the alignment of the stem between the planned and the actual results. Intra- and postoperative clinical parameters of surgery, including surgical time, intra-operative blood loss, complications, and the first ambulation, were also recorded to evaluate the safety of the surgery.
The preparation for PSI required an average of 3 days. 94% of cup size and 91% of stem size were correctly selected. The mean values of postoperative inclination and anteversion were 44.2° ± 4.1° and 19.2° ± 5.6°, respectively. 64.7% of cases deviated from planned within the ± 5
range and 94.1% within the ± 10° range. There was no significant statistical difference between the planned and the achieved values of stem anteversion, osteotomy height, and leg length discrepancy (p > 0.05). The average surgical time was 82.5° ± 10.8 min, and the intraoperative blood loss was estimated at 317.7° ± 57.6 ml. 64.7% of patients could walk on the day of surgery. There were no complications reported.
The point-of-care manufactured PSI is a useful solution for improving the accuracy of total hip arthroplasty surgery, especially in restoring implant orientation and reducing leg length discrepancy. However, long-term clinical follow-up evaluation is needed to confirm the efficacy and safety of this approach.
In this study, three typical cyclic siloxanes (CSis) were found in hair care products, indoor dust and indoor air samples at hair salons in Hanoi, Vietnam. The total concentrations of CSis in three ...kinds of hair care products ranged from 8.77 to 515 μg g−1. The mean and median concentrations of CSis in dust samples collected at hair salons were 671 and 654 μg g−1, respectively. The total concentrations of CSis in indoor air samples collected at the hair salons ranged from 415 to 2610 ng m−3 (mean: 1030; median: 849 ng m−3, respectively). Among three cyclic siloxanes mentioned in this study, decamethylcyclopentasiloxane (D5) was found at the highest level in all categories of samples. D5 had also a strong correlation between indoor dust and indoor air from hair salons (the coefficient of determination (R2): 0.852); meanwhile dodecamethylcyclohexasiloxane (D6) and octamethylcyclotetrasiloxane (D4) had good correlations (R2 = 0.618 and 0.585, respectively). This result indicates that hair care products are main emission source of cyclic siloxanes in indoor environments at the hair salons. The average exposure doses to total SCis through both of dust ingestion and inhalation were estimated to be 103 and 79.5 ng kg-bw−1 day−1 for women and men, respectively. These levels were higher than those reported for some Asian countries. This is among the most comprehensive investigations on the emission sources and distributions of cyclic siloxanes in indoor dust and indoor air at hair salons in Vietnam.
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•Total concentration of cyclic siloxanes in hair care products were up to 515 µg g−1.•High levels of CSis were found in indoor air samples.•D5 had strong concentration correlation between indoor air and dust samples collected from hair salons in Hanoi, Vietnam.•Estimated exposure doses to total CSis through inhalation for woman and man were respectively 103 and 79.5 ng kg-bw−1 d−1.
We studied sandfly (Diptera: Psychodidae) populations in six provinces of Vietnam. This work explores the diversity of sandfly species according to the province, as well as environment, and updated ...information on public health since leishmaniasis cases were reported in two provinces. Sandflies were collected using 428 CDC light traps from May 30 to October 13, 2016 and identified based on the morphology of the cibarium, pharynx and/or male genitalia or female spermathecae. A total of 2585 sandflies belonging to five genera and 13 identified species were collected. The main species were: the Sergentomyia barraudi group (12.53%), Se. sylvatica (9.63%) and Phlebotomus stantoni (3.95%). In all, 294 Sergentomyia specimens classified as Se. sp2 and Se. sp3 and a heterogeneous group, herein called Se. und_sp., showed unknown morphological characteristics requiring further studies. We provide detailed comments about morphological description and taxonomical identification in order to help standardization of sandfly classification in Southeast Asia. We observed differentiation according to the provinces in terms of density and species richness, with Lang Son having the highest density and Ninh Binh having the highest species richness. The majority of specimens were collected in rock caves and outdoors, suggesting mainly cavernicolous and exophilic characters of sandfly species in Northern Vietnam. However, specimens were also collected in intra- and peri-domiciliary sites. It is worth noting that Ph. stantoni was the main species found in dog sheds and indoors, and in particular in a leishmaniasis patient's house.
Concentrations of seven polybrominated diphenyl ethers (PBDEs) congeners were determined in surface sediments collected from several rivers and lakes in Hanoi, the capital city of Vietnam, to ...understand the status of background contamination, accumulation pattern, sources, and toxic implications for benthic organisms. Total PBDE concentrations in all sediment samples ranged from 0.03 to 17.5 ng/g dry weight (mean 1.33 ng/g dry wt). The most predominant congeners were BDE-47 and BDE-99, which comprised 30 and 25 % of total PBDE concentrations, respectively. Results from statistical analysis indicated that the potential sources of PBDEs of sediments in Hanoi may come from penta-BDE and octa-BDE mixtures. Risk quotients of PBDEs in sediments were also calculated for a benthic species, ranged from 2.12 × 10
−6
− 1.60 × 10
−2
, and were markedly lower than threshold value for occurrence of any ecotoxicological risk. This study provides some of the most comprehensive data on the occurrence of PBDEs in sediments from lake and river systems in Vietnam.
Earlier studies have reported the occurrence of cyclic and linear siloxanes in personal care and household products. Nevertheless, there is a lack of information on the occurrence of siloxanes in ...indoor air. In this study, four cyclic and six linear siloxanes were measured in 97 indoor air samples collected from various micro-environments in four cities in northern, Vietnam, during September 2016 to January 2017. The total concentrations of siloxanes (TSi) in particulate and gas phases ranged from 141 to 7220 μg g−1 (mean: 1880) and 23.8–1580 ng m−3 (mean: 321), respectively. The total concentrations of cyclic siloxanes (TCSi), linear siloxanes (TLSi), and TSi in indoor air were 1.91–1500 ng m−3, 21.8–817 ng m−3, and 41.8–1950 ng m−3, respectively. The highest mean concentration of siloxanes was found in indoor air from hair salons in Hanoi. The concentrations of siloxanes in air collected from homes in Hanoi were higher than those from other smaller cities such as Bacninh, Thaibinh, and Tuyenquang. The human exposures to siloxanes through inhalation were estimated for various age groups based on the measured concentrations. The mean inhalation exposure doses to total siloxanes for infants, toddlers, children, teenagers, and adults were 352, 219, 188, 132, and 95.9 ng kg-bw−1 d−1, respectively.
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•Siloxanes were found widely in indoor air from Northern in Vietnam.•Mean concentration of cyclic and linear siloxanes was 228 and 469 ng m−3, respectively.•The highest siloxanes concentrations were measured at hair salons.•The significant correlation existed between D4, D5, and D6 in indoor air.•Mean exposure dose to siloxanes through inhalation by infants was 1020 ng kg-bw−1 d−1.
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