Suppression of the alpha, delta, and omicron variants of SARS-Cov-2 in Taiwan.

BACKGROUND: Taiwan was a coronavirus disease 2019 (COVID-19) outlier, with an extraordinarily long transmission-free record: 253 days without locally transmitted infections while the rest of the world battled wave after wave of infection. The appearance of the alpha variant in May 2021, closely followed by the delta variant, disrupted this transmission-free streak. However, despite low vaccination coverage (<1%), outbreaks were well-controlled. METHODS: This study analyzed the time to border closure and conducted one-sample t test to compare between Taiwan and Non-Taiwan countries prior to vaccine introduction. The study also collected case data to observe the dynamics of omicron transmission. Time-varying reproduction number,Rt, was calculated and was used to reflect infection impact at specified time points and model trends of future incidence. RESULTS: The study analyzed and compare the time to border closure in Taiwan and non-Taiwan countries. The mean times to any border closure from the first domestic case within each country were -21 and 5.98 days, respectively (P < .0001). The Taiwanese government invested in quick and effective contact tracing with a precise quarantine strategy in lieu of a strict lockdown. Residents followed recommendations based on self-discipline and unity. The self-discipline in action is evidenced in Google mobility reports. The central and local governments worked together to enact non-pharmaceutical interventions (NPIs), including universal masking, social distancing, limited unnecessary gatherings, systematic contact tracing, and enhanced quarantine measures. The people cooperated actively with pandemic-prevention regulations, including vaccination and preventive NPIs. CONCLUSIONS: This article describes four key factors underlying Taiwan's success in controlling COVID-19 transmission: quick responses; effective control measures with new technologies and rolling knowledge updates; unity and cooperation among Taiwanese government agencies, private companies and organizations, and individual citizens; and Taiwanese self-discipline.

Comparison of polycyclic aromatic hydrocarbon accumulation in crab tissues with the ambient marine particles from shallow hydrothermal vents, northeast Taiwan.

This study investigated and compared polycyclic aromatic hydrocarbons (PAHs) in crab (Xenograpsus testudinatus), suspended particulate matter, and surface sediment sampled from Kuei-shan-tao (KST) shallow water vents just offshore northeast Taiwan. The total concentrations of PAHs (t-PAHs) in suspended particles near the vents (533-685 ng g-1 dw) were two orders of magnitude higher than the overlying sediment (3.42-6.06 ng g-1 dw). The t-PAHs in sediment were significantly lower than those found in suspended particulate matter and all crab tissues tested, including hepatopancreas (192-1154 ng g-1 dw), gill (221-748 ng g-1 dw), muscle (30-174 ng g-1 dw), and exoskeleton (22-96 ng g-1 dw). Principal component analysis (PCA) indicated tissue-specific bioaccumulation of PAHs in crabs. The compositions of PAHs in gill, muscle, and exoskeleton were mainly low molecular weight, while the composition in the hepatopancreas included both high and low molecular weight PAHs. Highly variable but characteristic PAH congeners and concentrations in crab tissues and ambient aquatic particles reflect bioaccumulation.

Contribution of Testing Strategies and Contact Tracing towards COVID-19 Outbreaks Control: A Mathematical Modeling Study.

This modeling study considers different screening strategies, contact tracing, and the severity of novel epidemic outbreaks for various population sizes, providing insight into multinational containment effectiveness of emerging infectious diseases, prior to vaccines development. During the period of the ancestral SARS-Cov-2 virus, contact tracing alone is insufficient to achieve outbreak control. Although universal testing is proposed in multiple nations, its effectiveness accompanied by other measures is rarely examined. Our research investigates the necessity of universal testing when contact tracing and symptomatic screening measures are implemented. We used a stochastic transmission model to simulate COVID-19 transmission, evaluating containment strategies via contact tracing, one-time high risk symptomatic testing, and universal testing. Despite universal testing having the potential to identify subclinical cases, which is crucial for non-pharmaceutical interventions, our model suggests that universal testing only reduces the total number of cases by 0.0009% for countries with low COVID-19 prevalence and 0.025% for countries with high COVID-19 prevalence when rigorous contact tracing and symptomatic screening are also implemented. These findings highlight the effectiveness of testing strategies and contact tracing in reducing COVID-19 cases by identifying subclinical cases.

A comprehensive evaluation of COVID-19 policies and outcomes in 50 countries and territories.

The COVID-19 pandemic struck the world unguarded, some places outperformed others in COVID-19 containment. This longitudinal study considered a comparative evaluation of COVID-19 containment across 50 distinctly governed regions between March 2020 and November 2021. Our analysis distinguishes between a pre-vaccine phase (March-November 2020) and a vaccinating phase (December 2020-November 2021). In the first phase, we develop an indicator, termed lockdown efficiency (LE), to estimate the efficacy of measures against monthly case numbers. Nine other indicators were considered, including vaccine-related indicators in the second phase. Linear mixed models are used to explore the relationship between each government policy & hygiene education (GP&HE) indicator and each vital health & socioeconomic (VH&SE) measure. Our ranking shows that surveyed countries in Oceania and Asian outperformed countries in other regions for pandemic containment prior to vaccine development. Their success appears to be associated with non-pharmaceutical interventions, acting early, and adjusting policies as needed. After vaccines have been distributed, maintaining non-pharmacological intervention is the best way to achieve protection from variant viral strains, breakthrough infections, waning vaccine efficacy, and vaccine hesitancy limiting of herd immunity. The findings of the study provide insights into the effectiveness of emerging infectious disease containment policies worldwide.

An Ultrasensitive Gateless Photodetector Based on the 2D Bilayer MoS2-1D Si Nanowire-0D Ag Nanoparticle Hybrid Structure.

Atomically thin transition metal dichalcogenides (TMDC) have received much attention due to their wide variety of optical and electronic properties. Among various TMDC materials, molybdenum disulfide (MoS2) has been intensely studied owing to its potential applications in nanoelectronics and optoelectronics. However, two-dimensional MoS2 photodetectors suffer from low responsivity due to low optical cross section. Combining MoS2 with plasmonic nanostructures can drastically increase scattering cross section and enhance local light-matter interaction. Moreover, suspended MoS2 has been shown to exhibit higher photoluminescence intensity and strong photogating effect, which can be employed in photodetectors. Herein, we propose an approach to utilize plasmonic nanostructures and physical suspension for 2D MoS2 photosensing enhancement by hybridizing 2D bilayer MoS2, 1D silicon nanowires, and 0D silver nanoparticles. The hybrid structure shows a gateless responsivity of 402.4 A/W at a wavelength of 532 nm, which represents the highest value among the ever reported gateless plasmonic MoS2 photodetector. The great responsivity and large active area results in an exceptional detectivity of 2.34 × 1012 Jones. This study provides a new approach for designing high-performance 2D TMDC-based optoelectronic devices.

Nonpolio Enterovirus Activity during the COVID-19 Pandemic, Taiwan, 2020.

In Taiwan, lower nonpolio enterovirus activity during the coronavirus disease pandemic in 2020 compared with 2014-2019 might be attributable to adherence to nonpharmaceutical interventions. The preventable fraction among unexposed persons indicated that 90% of nonpolio enterovirus activity might have been prevented during 2014-2019 by adopting the same measures enforced in 2020.

The effect of preventing subclinical transmission on the containment of COVID-19: Mathematical modeling and experience in Taiwan.

The control strategies preventing subclinical transmission differed among countries. A stochastic transmission model was used to assess the potential effectiveness of control strategies at controlling the COVID-19 outbreak. Three strategies included lack of prevention of subclinical transmission (Strategy A), partial prevention using testing with different accuracy (Strategy B) and complete prevention by isolating all at-risk people (Strategy C, Taiwan policy). The high probability of containing COVID-19 in Strategy C is observed in different scenario, had varied in the number of initial cases (5, 20, and 40), the reproduction number (1.5, 2, 2.5, and 3.5), the proportion of at-risk people being investigated (40%, 60%, 80%, to 90%), the delay from symptom onset to isolation (long and short), and the proportion of transmission that occurred before symptom onset (<1%, 15%, and 30%). Strategy C achieved probability of 80% under advantageous scenario, such as low number of initial cases and high coverage of epidemiological investigation but Strategy B and C rarely achieved that of 60%. Considering the unsatisfactory accuracy of current testing and insufficient resources, isolation of all at-risk people, as adopted in Taiwan, could be an effective alternative.

Real-time dengue forecast for outbreak alerts in Southern Taiwan.

Dengue fever is a viral disease transmitted by mosquitoes. In recent decades, dengue fever has spread throughout the world. In 2014 and 2015, southern Taiwan experienced its most serious dengue outbreak in recent years. Some statistical models have been established in the past, however, these models may not be suitable for predicting huge outbreaks in 2014 and 2015. The control of dengue fever has become the primary task of local health agencies. This study attempts to predict the occurrence of dengue fever in order to achieve the purpose of timely warning. We applied a newly developed autoregressive model (AR model) to assess the association between daily weather variability and daily dengue case number in 2014 and 2015 in Kaohsiung, the largest city in southern Taiwan. This model also contained additional lagged weather predictors, and developed 5-day-ahead and 15-day-ahead predictive models. Our results indicate that numbers of dengue cases in Kaohsiung are associated with humidity and the biting rate (BR). Our model is simple, intuitive and easy to use. The developed model can be embedded in a "real-time" schedule, and the data (at present) can be updated daily or weekly based on the needs of public health workers. In this study, a simple model using only meteorological factors performed well. The proposed real-time forecast model can help health agencies take public health actions to mitigate the influences of the epidemic.