Dengue is the most prevalent arboviral disease of humans. The host and virus variables associated with dengue virus (DENV) transmission from symptomatic dengue cases (n = 208) to Aedes aegypti mosquitoes during 407 independent exposure events was defined. The 50% mosquito infectious dose for each of DENV-1-4 ranged from 6.29 to 7.52 log10 RNA copies/mL of plasma. Increasing day of illness, declining viremia, and rising antibody titers were independently associated with reduced risk of DENV transmission. High early DENV plasma viremia levels in patients were a marker of the duration of human infectiousness, and blood meals containing high concentrations of DENV were positively associated with the prevalence of infectious mosquitoes 14 d after blood feeding. Ambulatory dengue cases had lower viremia levels compared with hospitalized dengue cases but nonetheless at levels predicted to be infectious to mosquitoes. These data define serotype-specific viremia levels that vaccines or drugs must inhibit to prevent DENV transmission.engue is globally the most important mosquito-borne viral disease of humans, with a global burden of ∼100 million cases per annum (1, 2). Aedes aegypti mosquitoes are the primary mosquito vectors of dengue viruses (DENV), of which there are four virus types (DENV-1-4). Multiple factors influence the likelihood of infection and dissemination of DENV in Ae. aegypti and include the amplitude of daily temperature fluctuations (3), mean temperature (4), and the genotype of mosquito and virus (5), among others (6). The extrinsic incubation period (EIP), a critical determinant of vector competence (7,8), is widely accepted to be 7-14 d for DENV in Ae. aegypti, although a recent modeling analysis of historical DENV transmission data has suggested a wider range of 2-15 d at 30°C (9). A major caveat to many of these observations is that they stem from laboratory experiments with artificially generated virus-spiked blood meals and often in-bred colony mosquitoes.The temporal and virological variables associated with the transmission of DENV from a naturally infected human to a biting Ae. aegypti mosquito are poorly understood. Natural history studies of experimental DENV infection of small cohorts of human volunteers in the 1920s by Siler et al. (10,11), likely using DENV-4 (12), and subsequent studies by Simmons et al. (13), likely using DENV-1 (12), suggested that the window of time before the onset of clinical symptoms that DENV-1 or DENV-4 could be transmitted to Ae. aegypti mosquitoes was 6-18 h or 2 d, respectively (14). After fever onset, the duration of infectiousness was 4-5 d for DENV-1 and up to 2 d for DENV-4, with an EIP in the mosquito of 10 d or more. Consistent with this, mosquitobiting studies by Gubler et al. in the 1960s (15-18) collectively estimated that dengue cases were infectious for 4-5 d after illness onset (range, 2-12 d). The human viremia level required to infect Ae. aegypti mosquitoes is unknown, and therefore it is uncertain what percentage of symptomatic (or asymptomatic...

Background. Dengue is the most common arboviral infection of humans. There are currently no specific treatments for dengue. Balapiravir is a prodrug of a nucleoside analogue (called R1479) and an inhibitor of hepatitis C virus replication in vivo.Methods. We conducted in vitro experiments to determine the potency of balapiravir against dengue viruses and then an exploratory, dose-escalating, randomized placebo-controlled trial in adult male patients with dengue with <48 hours of fever.Results. The clinical and laboratory adverse event profile in patients receiving balapiravir at doses of 1500 mg (n = 10) or 3000 mg (n = 22) orally for 5 days was similar to that of patients receiving placebo (n = 32), indicating balapiravir was well tolerated. However, twice daily assessment of viremia and daily assessment of NS1 antigenemia indicated balapiravir did not measurably alter the kinetics of these virological markers, nor did it reduce the fever clearance time. The kinetics of plasma cytokine concentrations and the whole blood transcriptional profile were also not attenuated by balapiravir treatment.Conclusions. Although this trial, the first of its kind in dengue, does not support balapiravir as a candidate drug, it does establish a framework for antiviral treatment trials in dengue and provides the field with a clinically evaluated benchmark molecule.Clinical Trials Registration. NCT01096576.

SignificanceIn laboratory experiments, Wolbachia (wMel strain)-infected Aedes aegypti are refractory to disseminated arboviral infections. Yet previous characterizations of wMel-mediated blocking have not considered several biologically and ecologically important factors likely to influence the virus–mosquito interaction. After direct feeding on 141 viremic dengue patients, we demonstrate wMel lowers dengue virus (DENV) transmission potential and lengthens the extrinsic incubation period. Subsequently, using established field populations of wild-type and wMel-infected Ae. aegypti, we compared field- versus laboratory-rearing conditions on mosquito susceptibility to disseminated DENV infection. The magnitude of wMel-mediated virus blocking was even greater when mosquitoes developed under field conditions. These clinically and ecologically relevant findings support Wolbachia introgression into Ae. aegypti populations as a biocontrol method to reduce the transmission of DENV and other arboviruses.

Emerging from early of 2020, the COVID-19 pandemic has become one of the most serious health crisis globally. In response to such threat, a wide range of digital health applications has been deployed in Vietnam to strengthen surveillance, risk communication, diagnosis, and treatment of COVID-19. Digital health has brought enormous benefits to the fight against COVID-19, however, numerous constrains in digital health application remain. Lack of strong governance of digital health development and deployment; insufficient infrastructure and staff capacity for digital health application are among the main drawbacks. Despite several outstanding problems, digital health is expected to contribute to reducing the spread, improving the effectiveness of pandemic control, and adding to the dramatic transformation of the health system the post-COVID era.

Objective To estimate the incubation period of Vietnamese confirmed COVID-19 cases. Methods Only confirmed COVID-19 cases who are Vietnamese and locally infected with available data on date of symptom onset and clearly defined window of possible SARS-CoV-2 exposure were included. We used three parametric forms with Hamiltonian Monte Carlo method for Bayesian Inference to estimate incubation period for Vietnamese COVID-19 cases. Leave-one-out Information Criterion was used to assess the performance of three models. Results A total of 19 cases identified from 23 Jan 2020 to 13 April 2020 was included in our analysis. Average incubation periods estimated using different distribution model ranged from 6.0 days to 6.4 days with the Weibull distribution demonstrated the best fit to the data. The estimated mean of incubation period using Weibull distribution model was 6.4 days (95% credible interval (CrI): 4.89–8.5), standard deviation (SD) was 3.05 (95%CrI 3.05–5.30), median was 5.6, ranges from 1.35 to 13.04 days (2.5th to 97.5th percentiles). Extreme estimation of incubation periods is within 14 days from possible infection. Conclusion This analysis provides evidence for an average incubation period for COVID-19 of approximately 6.4 days. Our findings support existing guidelines for 14 days of quarantine of persons potentially exposed to SARS-CoV-2. Although for extreme cases, the quarantine period should be extended up to three weeks.

The coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global health concern. The development of vaccines with high immunogenicity and safety is crucial for controlling the global COVID-19 pandemic and preventing further illness and fatalities. Here, we report the development of a SARS-CoV-2 vaccine candidate, Nanocovax, based on recombinant protein production of the extracellular (soluble) portion of the spike (S) protein of SARS-CoV-2. The results showed that Nanocovax induced high levels of S protein-specific IgG and neutralizing antibodies in three animal models: BALB/c mouse, Syrian hamster, and a non-human primate (Macaca leonina). In addition, a viral challenge study using the hamster model showed that Nanocovax protected the upper respiratory tract from SARS-CoV-2 infection. Nanocovax did not induce any adverse effects in mice (Mus musculus var. albino) and rats (Rattus norvegicus). These preclinical results indicate that Nanocovax is safe and effective.

PurposeThis study aims to develop a strategic framework for the success of coastal urban projects in Vietnam, which is one of the Asia Pacific countries significantly affected by climate change.Design/methodology/approachA questionnaire was used to collect data from practitioners in Vietnam. Principal component analysis (PCA) technique was used to identify critical success factors (CSFs) of coastal urban projects. A strategy map for the success of coastal urban projects was also proposed using the balanced scorecard (BSC) method.FindingsThis study identified 41 project success factors that could contribute to project success, and thence, extracted 11 CSFs for coastal urban projects using the PCA technique. In addition, 11 key performance indicators (KPIs) for coastal urban projects were listed and their linking with project success factors and CSFs was explored. Furthermore, a strategy map for the success of coastal urban projects was proposed using the BSC method. The strategy map included five perspectives: learning and growth, internal processes, social and environmental performance, financial performance, and stakeholders' satisfaction.Originality/valueThis study identified 11 CSFs for coastal urban projects and proposed a strategy map for the success of coastal urban projects.

The benefits of using mineral additive as a partial replacement for cement in heavyweight concrete are discussed. This paper presents the strength development and temperature distribution of concrete using Class F of natural pozzolan (PU) sourced from Northern part of Vietnam. Based on the results of conducted studies, strengths of the natural pozzolan concrete at different ages were generally lower than those of control concrete. The 7-day compressive strengths of concrete with 20% PU decreases mostly by 30.1% and least by 12.3% at the age of 28 days in comparison with control concrete. However, natural pozzolan increases the workability of fresh concrete up to 16.67% in comparison with control concrete. By using the computer program Midas Civil, the maximum temperatures at the center of concrete block with 100% cement and of concrete block with 80% cement + 20% PU are 65.7600C and 52.4400C, respectively, after 48 hours from the beginning of pouring. In addition, temperature difference between the central point and the environmental temperature of the control concrete are higher than heavyweight concrete using 20% PU. Meaningfully, the risk of through thermal cracking of heavyweight concrete without pozzolan are higher than heavyweight concrete PU to replace 20% of mass cement.