Increase In Transmission Rate Research Articles

Correlation Between Climate Change and Parasitic Infections in Australian

Purpose: To aim of the study was to analyze the correlation between climate change and parasitic infections in Australian. Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: The correlation between climate change and parasitic infections in Australia reveals significant relationships influenced by changing environmental conditions. Research indicates that rising temperatures and altered rainfall patterns create favorable habitats for parasites and their vectors, leading to increased transmission rates of diseases such as Ross River virus and malaria. Additionally, extreme weather events, such as floods and droughts, contribute to the spread of waterborne parasites and disrupt traditional patterns of infection. The findings suggest that as climate change continues to impact Australia, public health systems may face heightened challenges in managing and mitigating the risks associated with parasitic infections. Unique Contribution to Theory, Practice and Policy: Ecological niche theory, disease ecology theory & one health concept may be used to anchor future studies on correlation between climate change and parasitic infections in Australian. Implement and refine surveillance systems that monitor parasitic infections in relation to climate data. Advocate for the integration of climate change considerations into health policies related to parasitic infections.

Analyzing the dynamics and optimal control of a vector-borne model with dual vertical transmission and multiple serotypes

Abstract Transmission and contact patterns have an important influence on the intensity and trend of disease transmission. Taking into account two different serotypes and the vertical transmission of the disease in both humans and mosquitoes, this paper proposes a novel vector-borne disease model. In order to explore the evolution mechanisms of the model and the impacts of contact pattern on disease transmission. The basic regeneration number of the proposed model is obtained via the next-generation matrix approach. Subsequently, we analyze the conditions of the stabilities and existences of the equilibrium points. Further, the sensitivity of the parameters is studied using numerical simulations. It is observe that the increase of vertical transmission rate of mosquitoes leads to the increase of the basic reproduction number. In addition, we develop vaccination and insecticide control strategies and derive the existence and expression of the optimal solution. Our numerical results show that vaccination has a little effect on preventing the spread of disease among mosquitoes. However, insecticide spraying is effective in reducing the spread of disease between humans and mosquitoes.

High-Speed Signal Optimization at Differential VIAs in Multilayer Printed Circuit Boards

The number of Printed Circuit Board (PCB) layers is continually increasing with the increase in data transmission rates, and the Signal Integrity (SI) of high-speed digital systems cannot be ignored. Introducing Vertical Interconnect Accesses (VIAs) in PCBs can realize the electrical connection between the top layer and the inner layers, however, VIAs represent one of the most important reasons for discontinuity between the PCBs and package. In this paper, a new optimization scheme for a differential VIA stub is proposed, with 3D full-wave numerical simulation used for modeling and simulation. Results show that this scheme optimizes the return loss and insertion loss while making the signal eye diagram more ideal, which can improve the transmission effect of high-speed signals.

Early detection of highly transmissible viral variants using phylogenomics.

As demonstrated by the SARS-CoV-2 pandemic, the emergence of novel viral strains with increased transmission rates poses a serious threat to global health. Statistical models of genome sequence evolution may provide a critical tool for early detection of these strains. Using a novel stochastic model that links transmission rates to the entire viral genome sequence, we study the utility of phylogenetic methods that use a phylogenetic tree relating viral samples versus count-based methods that use case counts of variants over time exclusively to detect increased transmission rates and identify candidate causative mutations. We find that phylogenies in particular can detect novel transmission-enhancing variants very soon after their origin and may facilitate the development of early detection systems for outbreak surveillance.

Biobased rubber toughened poly(lactic acid) blend for sustainable packaging films: The role of optical purity of poly(lactic acid)

AbstractThis study investigates the novel effect of poly(lactic acid) (PLA) optical purity on PLA/liquid natural rubber (LNR) blend films fabricated by solution casting. An investigation was conducted to examine how different levels of PLA optical purity affect the mechanical, structural, morphological, thermal, and barrier properties of PLA/LNR films. Infrared spectroscopy analysis revealed that the D‐isomer content of PLA significantly affected the chemical interactions between the LNR and PLA. The favorable chemical interaction between the LNR and PLA with a high D‐isomer content also increased the elongation at break by 300%. Morphological investigations proved that the chemical interaction also improved the dispersion and reduced the size of the LNR droplets formed in the PLA matrix. Notably, while low D‐isomer PLA blends showed decreased crystallinity (Xc) upon LNR addition, high D‐isomer PLA blends exhibited increased Xc by 460%, leading to a 42% increase in oxygen transmission rate. Additionally, hydrolytic degradation of high D‐isomer PLA increased by 259% with increasing LNR content. Overall, optical purity of PLA plays an important role in determining the properties of PLA blends.

Research on high-speed digital optical signal jitter measurement technology based on clock recovery algorithm using eye diagram opening area

With the rapid development of information technology, high-speed digital optical signal transmission technology has become the core of modern communication networks. However, the increase in transmission rates brings challenges such as noise, distortion, and interference, which affect the accuracy of clock recovery. To address these issues, this study proposes a clock recovery algorithm based on the eye diagram opening area to improve the accuracy and efficiency of high-speed digital optical signal jitter measurement. The proposed method extracts clock information from the signal using the opening area and curvature characteristics of the eye diagram for jitter measurement. Experimental results demonstrate that the clock recovery algorithm based on the eye diagram opening area can stably reconstruct the signal eye diagram and obtain jitter parameters under different optical power conditions. At optical powers of −7.2 dBm, −12.2 dBm, and −17.2 dBm, the Q-factors were 8.8, 7.6, and 4.3, respectively, and the RMS jitter values were 12.2 ps, 13.4 ps, and 21.2 ps, respectively. At optical powers of −2.3 dBm, 0.1 dBm, 2.4 dBm, 4.6 dBm, and 6.0 dBm, the Q-factors were 9.1, 9.3, 9.5, 9.7, and 10.0, respectively, and the average jitter values were 8.9 ps, 8.5 ps, 8.0 ps, 7.5 ps, and 7.0 ps. These results indicate that the proposed algorithm performs excellently under low optical power conditions and maintains high recovery accuracy even when jitter increases at higher optical powers. The clock recovery algorithm based on the eye diagram opening area significantly improves the accuracy and stability of high-speed digital optical signal jitter measurement, enriches the theoretical research of clock recovery algorithms, and shows significant advantages in improving signal transmission quality, reducing bit error rate, and enhancing communication link reliability. The research outcomes provide key technical support for the optimization of modern high-speed optical communication systems.

Dual Guardians of Immunity: FoRab10 and FoRab29 in Frankliniella occidentalis Confer Resistance to Tomato Spotted Wilt Orthotospovirus.

Rab GTPase is critical for autophagy processes and is implicated in insect immunity against viruses. In this study, we aimed to investigate the role of FoRabs in the autophagic regulation of antiviral defense against tomato spotted wilt orthotospovirus (TSWV) in Frankliniella occidentalis. Transcriptome analysis revealed the downregulation of FoRabs in viruliferous nymph and adults of F. occidentalis in response to TSWV infection. Manipulation of autophagy levels with 3-MA and Rapa treatments resulted in a 5- to 15-fold increase and a 38-64% decrease in viral titers, respectively. Additionally, interference with FoRab10 in nymphs and FoRab29 in adults led to a 20-90% downregulation of autophagy-related genes, a decrease in ATG8-II (an autophagy marker protein), and an increase in the TSWV titers by 1.5- to 2.5-fold and 1.3- to 2.0-fold, respectively. In addition, the leaf disk and the living plant methods revealed increased transmission rates of 20.8-41.6 and 68.3-88.3%, respectively. In conclusion, FoRab10 and FoRab29 play a role in the autophagic regulation of the antiviral defense in F. occidentalis nymphs and adults against TSWV, respectively. These findings offer insights into the intricate immune mechanisms functional in F. occidentalis against TSWV, suggesting potential targeted strategies for F. occidentalis and TSWV management.

Multi-path serial tasks offloading strategy and dynamic scheduling optimization in vehicular edge computing networks

Vehicular edge computing networks (VECNs) can provide a promising solution to support efficient task execution of vehicles. Consider the channel and access time variations caused by the high mobility of vehicles in a vehicular environment when designing task offloading strategies in VECNs. In this paper, we perform multi-path offloading for a task vehicle with serial tasks based on both dynamic communication distances of vehicle-to-infrastructure (V2I) links, that of vehicle-to-vehicle (V2V) links, and slowly varying large-scale fading information of wireless channels. Considering the task vehicle's low delay requirements, our goal is to minimize the maximum task completion time of the task vehicle. A multi-path dynamic offloading scheme (MPDOS), composed of three parts, is proposed to achieve maximum delay minimization. The maximum processing capability of links between a task vehicle and roadside units (RSUs) is first taken as the objective to find the required communication links, which can decrease the total processing time by increasing transmission rate and execution capacity. Then, a task allocation scheme based on a multi-knapsack algorithm matches tasks and RSUs. Finally, a balancing scheme is leveraged to provide load-balancing computing performance across all computation devices. Numerical results show that our proposed scheme outperforms 30.7% of the RA algorithm, and the task completion rate can reach 99.55%.

Comparative investigation of activation energy and biot number on quadratic convective flow of a radiating micropolar fluid

In this study, we evaluate the significance of activation energy for initiating a chemical reaction in a two-dimensional laminar flow of a micropolar fluid over a semi-infinite inclined plate. The internal heat transfer mechanism of fluid is modeled with considerations of radiation and convective thermal boundary conditions. The momentum equation uses quadratic density relations in the concentration and temperature differences in buoyancy. In addition, flow through a porous medium surrounded by an inclined plate is modeled by the Darcy-Forchheimer model. Using a spectral successive linearization approach achieves the numerical results for the dimensionless equations. Basic characteristics of flow are examined for a range of dimensionless physical parameters. Quadratic convection is observed to have a stronger impact on the physical components of the flow than linear convection. In addition, compared to the linear illustration, the quadratic convection scenario results in a 14 % − 19 % increase in surface drag and heat transmission rate and a 5 % − 9 % decrease in mass transfer rate. Further, a higher activation energy corresponds with a higher concentration of micropolar fluid. Furthermore, as the radiation and Biot number rise, the velocity and rate of heat transfer correspondingly increase. We believe that the obtained results apply to aerosol technologies and polymeric mixtures used under extreme temperatures and concentrations.

Retrospective Cohort Study on the Impact of the COVID-19 Pandemic on Pregnancy Outcomes for Women Living With HIV in British Columbia.

For pregnant women living with HIV (WLWH), engagement in care is crucial to maternal health and reducing the risk of perinatal transmission. To date, there have been no studies in Canada examining the impact of the COVID-19 pandemic on pregnant WLWH. This was a retrospective cohort study assessing the impact of the pandemic on perinatal outcomes for pregnant WLWH using data from the Perinatal HIV Surveillance Program in British Columbia, Canada. We compared maternal characteristics, pregnancy outcomes, and clinical indicators related to engagement with care between a prepandemic (January 2017-March 2020) and pandemic cohort (March 2020-December 2022). We investigated preterm birth rates with explanatory variables using logistic regression analysis. The prepandemic cohort (n = 87) had a significantly (P < 0.05) lower gestational age at the first antenatal encounter (9.0 vs 11.8) and lower rates of preterm births compared with the pandemic cohort (n = 56; 15% vs 37%). Adjusted odds of preterm birth increased with the presence of substance use in pregnancy (aOR = 10.45, 95% confidence interval: 2.19 to 49.94) in WLWH. There were 2 cases of perinatal transmission of HIV in the pandemic cohort, whereas the prepandemic cohort had none. The pandemic had pronounced effects on pregnant WLWH and their infants in British Columbia including higher rates of preterm birth and higher gestational age at the first antenatal encounter. The nonstatistically significant increase in perinatal transmission rates is of high clinical importance.

Influence of thermal radiation and shape factor on a hybrid nanofluid flow over a permeable flat plate with cross-diffusion effects: An irreversibility analysis

Understanding and controlling the shape factors of nanoparticles in fluid flow problems is crucial for optimizing heat transfer, fluid dynamics, and various applications such as nanofluids, drug delivery systems, catalysis, and nanocomposites. By tailoring the shape of nanoparticles, researchers can manipulate their behavior, dispersion, and interaction with the fluid, thereby optimizing the desired outcomes in various fluid flow problems. The meticulous investigation uncovers the integration of entropy analysis in the investigation of the flow of convective magnetohydrodynamic hybrid nanofluid via a permeable flat surface, by considering the effects of Dufour, viscous dissipation, Soret, and thermal radiation. The governing equations are converted into a set of nonlinear ordinary differential equations using appropriate similarity transformations and then solved using the bvp4c solver, a MATLAB in-built function. We display the outcomes for three different shape factors: platelet, cylinder, and brick. The skin friction coefficient increases at a rate of 1.5089 for the brick shape, 1.5163 for the cylindrical shape, and 1.5212 for the platelet shape when the mixed convection parameter lies between 1 and 5. In this regard, it is important to point out that there is a direct connection between the increase in temperature transmission rate and a decline in the Dufour number ( Du ). It has been found that when 1 ≤ Du ≤ 2.4 , the Nusselt number decreases by 0.4786, 0.4618, and 0.4512 for brick, cylinder, and platelet shapes, respectively. A decline in the Sherwood number is noticed with an upsurge in the Soret number ( Sr ). There is a noticeable increase of 0.0442 in the Sherwood number for brick shape, 0.0438 for cylinder form, and 0.0435 for platelet form when 1 ≤ Du ≤ 2.4 . Furthermore, we have detected that an increase in the radiation parameter amplifies both the Bejan number and the profiles of entropy formation.

Pathogen evolution following spillover from a resident to a migrant host population depends on interactions between host pace of life and tolerance to infection.

Changes to migration routes and phenology create novel contact patterns among hosts and pathogens. These novel contact patterns can lead to pathogens spilling over between resident and migrant populations. Predicting the consequences of such pathogen spillover events requires understanding how pathogen evolution depends on host movement behaviour. Following spillover, pathogens may evolve changes in their transmission rate and virulence phenotypes because different strategies are favoured by resident and migrant host populations. There is conflict in current theoretical predictions about what those differences might be. Some theory predicts lower pathogen virulence and transmission rates in migrant populations because migrants have lower tolerance to infection. Other theoretical work predicts higher pathogen virulence and transmission rates in migrants because migrants have more contacts with susceptible hosts. We aim to understand how differences in tolerance to infection and host pace of life act together to determine the direction of pathogen evolution following pathogen spillover from a resident to a migrant population. We constructed a spatially implicit model in which we investigate how pathogen strategy changes following the addition of a migrant population. We investigate how differences in tolerance to infection and pace of life between residents and migrants determine the effect of spillover on pathogen evolution and host population size. When the paces of life of the migrant and resident hosts are equal, larger costs of infection in the migrants lead to lower pathogen transmission rate and virulence following spillover. When the tolerance to infection in migrant and resident populations is equal, faster migrant paces of life lead to increased transmission rate and virulence following spillover. However, the opposite can also occur: when the migrant population has lower tolerance to infection, faster migrant paces of life can lead to decreases in transmission rate and virulence. Predicting the outcomes of pathogen spillover requires accounting for both differences in tolerance to infection and pace of life between populations. It is also important to consider how movement patterns of populations affect host contact opportunities for pathogens. These results have implications for wildlife conservation, agriculture and human health.

Optimization of Higher Education Teaching Methodology System Based on Edge Intelligence

Abstract This study provides an in-depth research on the dynamic allocation of resources in higher education teaching and learning, especially in the application of edge intelligence architecture. In the study, the characteristics of edge intelligence and its application in smart mobile devices (SMDs) are first analyzed, highlighting the role of mobile edge computing (MEC) in reducing latency and improving the quality of user experience. Then, the study adopts a data acquisition method based on deep neural network (DNN) model to optimize the edge training model. The experimental results show that the efficiency of edge computing can be significantly improved by optimizing the allocation of computing resources and reducing the data transmission delay. Specifically, the total training delay and energy consumption of the edge server are reduced under different global iteration numbers in the experiment. In addition, the study also explores the integration of 5G networks and AR/VR technology in education. It proposes a teaching optimization model based on edge intelligence, improving interaction quality and learning efficiency in AR/VR safety education classrooms. The study shows that the teaching model performs well in reducing latency and increasing transmission rate, which is especially suitable for dual-teacher classroom scenarios and provides a new perspective for future higher education teaching.

Effectiveness of contact tracing for COVID-19 in Belgium

Contact tracing and investigation can prevent infectious disease transmission when carried out promptly. Data obtained from contact tracing also provides unique information on transmission dynamics that can be useful for policy making. The proportion of secondary infections arising from index cases that were previously identified as a close contact, hence “known index cases”, has been indicated by ECDC as a key performance indicator for contact tracing. Few empirical studies have been published on the effectiveness of contact tracing and investigation during the COVID-19 pandemic.&#x0D; Using data from the Belgian COVID-19 contact tracing (Sept 2020 – Dec 2021), we investigated the impact of contact tracing on onward transmission. Known index cases were compared to those not previously identified as close contact. More specifically, we compared their traced contacts and secondary cases as well as the serial interval, representing the time from illness onset in the primary case to illness onset in the secondary case. In addition, we investigated contact and transmission characteristics by age.&#x0D; Known index cases, previously informed about their exposure, were linked to fewer high-risk contacts and secondary infections. In addition, they presented a lower secondary attack rate compared to those not previously identified by contact investigation, suggesting behavioural changes. Also, a shorter serial interval was observed for known index cases. In addition to breaking transmission chains, contact tracing provides important information on transmission characteristics. When exploring age-specific data, we observed increased transmission rates from children to adults during the circulation of Delta and Omicron variants without an increase in contact rates between these age groups.&#x0D; The lower secondary attack rates for known index cases suggest that contact tracing in Belgium has been effective in reducing onward transmission. Their lower number of traced contacts and shorter serial interval are indicative that individuals aware of their exposure to SARS-CoV-2 were more reserved in their social contact behaviour. This reflects the mandatory quarantine for high-risk contacts. Our study also shows that in times of high burden on the healthcare system, key performance indicators of contact tracing should be interpreted with caution in light of changing intervention strategies. Many external factors influence the effectiveness of contact tracing like testing policy and compliance, the cooperation of index cases, and the imposed and adopted quarantine and isolation policies.&#x0D;

A signal processing method for continuous mud pressure wave signals in logging-while-drilling systems

For signal transmission of mud pressure waves in logging-while-drilling systems, as more measurement parameters are adopted, the conventional signal transmission rate of approximately 1 bps cannot meet the requirements of parameter uploading. Transmission rates greater than 10 bps are widely used by current Chinese and international enterprises in their continuous wave transmission systems. Due to the increasing transmission rates, a conventional single-channel pressure sensor cannot effectively identify the key features of an original signal with a low signal-to-noise ratio at a high transmission rate. This issue results in a low success rate for pressure wave recognition and decoding. This paper addresses a method for the collection of pressure wave signals using multi-channel pressure sensors through the analysis of the signal transmission changes of mud pressure waves with well depths and echo interference caused by drilling rod reflection. In this research, numerical simulation and experimental verification were used to calculate the cross-correlations of the multi-channel signals to effectively remove interference noises such as reflective waves and improve the signal-to-noise ratio of the original signal. The results showed that this method could effectively improve the SNR after the wave filtering of the original pressure wave. The characteristics of the continuous mud pressure wave signals were analysed using a circulation test. A corresponding band-pass filter was designed to remove pump noises to restore the sinusoidal pressure wave signal required by the original transmission rules.

Partial filterable optical networking: A gradual upgrade scheme for large-scale backbone networks

Widespread commercialization of 5G/F5G access networks requires the upgrade of optical backbone networks. Besides increasing transmission rate of optical communication system, increasing number of nodes is also a suitable way to upgrade optical backbone networks. Since building a large-scale network in one step is very expensive, we introduce a gradual backbone network upgrade scheme named partial filterable optical networking (PFON) in this paper. In the PFON scheme, only part of nodes are filterable nodes deployed with bandwidth-variable spectrum selective switches, so networking cost can be greatly reduced. Furthermore, we divide the planning problem of PFON into two subproblems, namely filterable node selection subproblem and spectrum assignment subproblem. For the first subproblem, a heuristic algorithm is designed; for the second subproblem, an integer non-linear programming model and a heuristic algorithm are respectively proposed for small and large networks. Performance results show that the PFON scheme can make a tradeoff between networking cost and spectrum consumption, by properly setting the number of filterable nodes.

Prevalence of dengue fever in Saudi Arabia: Jeddah as a case study

AbstractDengue fever is widespread in tropical and subtropical regions, including Saudi Arabia. Aedes aegypti (Diptera: Culicidae) transmits dengue and many other diseases, including chikungunya and Zika. This study provides an overview of dengue fever in Saudi Arabia since the first case was recorded in the early 1990s. In addition, it focuses on the epidemiological situation in Jeddah as a case study to study the spatial distribution of dengue cases using Geographic Information Systems (GIS) techniques over 5 years, from 2019 to 2023. The first recorded case in Saudi Arabia was in October 1993; however, daily data indicates that 2023 is a major epidemic year. The number of infections has reached 4099 so far during the first half of the year, which indicates a significant increase compared to previous years. GIS analysis has unveiled the locations of high infection rates across multiple municipalities, commonly called hotspots, and identified areas where dengue cases remain relatively low. The Inverse Distance Weighted (IDW) tool was used to determine the severity of infection in different areas of Jeddah. The study concluded that factors such as temperature, rainfall, and septic tanks in areas that lack a proper sanitation network are the most contributing factors to the spread of disease vectors and, thus, dengue. Winter rainfall creates conducive breeding environments for dengue mosquito vectors, increasing transmission rates. On the other hand, summer heat accelerates the mosquito life cycle and enhances viral replication, heightening the risk of dengue transmission.

Impact of vaccination on the entire population and dose-response relation of COVID-19

ObjectiveThe objective of this study is to develop a mathematical model for the COVID-19 pandemic including vaccination, the transmissibility of the virus-pathogen dose-response relationship, vaccine efficiency, and vaccination rate. MethodsThe Runge-Kutta (RK-45) method was applied to solve the proposed model with MATLAB code and the calculated results show the dynamics of the individuals in each compartment. The data of total death due to the COVID-19 pandemic in the case of the USA were collected from GitHub and the re-use of this data needs no ethical clearance. The control reproduction number was used to assess the dose-response relationship and critical vaccination coverage. ResultsWe have calculated the probability of infection and the infection risk against the different exposure doses and the virus copies, respectively. The results show that the probability of infection increases with the increasing exposure dose for certain virus copies and the risk of infection decreases with the increasing of virus copies for a certain exposure dose. The results also show that the critical vaccination coverage demands increase with an increase in transmission rate and decrease with increasing vaccine efficacy. ConclusionsIt was seen that the critical vaccination coverage corresponding to an increased transmission rate rise sharply in the beginning and then reached a threshold. Moreover, the real data of the total death cases in the USA were compared with the fitted curved of the model which validated the proposed model. Vaccination against COVID-19 is essential to control the pandemic, and achieving high vaccine uptake in the population can reduce the pandemic as fast as possible.

Is the BNT162b2 vaccine still effective against the latest variant: XBB.1.5?

The XBB.1.5 sub-variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron now continues to spread rapidly due to the increased transmission rate as a result of increased affinity of the virus binding over the ACE-2 receptor - a gained property due to the mutation that occurred in spike protein. The protectivity of BNT162b2 antibodies produced in the serum of patients is an important parameter for preventing transmission. However, the affinity of the antibodies of patients vaccinated with BNT162b2 over the latest SARS-CoV-2 variant, XBB.1.5, is not well established. This study aimed to evaluate the efficacy of the BNT162b2 vaccine-induced antibody on XBB.1.5 by comparing the X-ray crystallographic structures and spike protein mutations of BA.5 and XBB.1.5 using in silico methods. Binding points and binding affinity values of the BNT162b2 antibody with BA.5 and XBB.1.5 spike protein were calculated using ClusPro 2.0 protein-protein docking and Discovery Studio 2021 Client software. Mutations in the genetic code of the spike protein for SARS-CoV-2 BA.5 and XBB.1.5 sub-variants were screened using the GISAID database. Binding affinity values showed that BNT162b2 had higher negative values in the XBB.1.5 sub-variant than BA.5 at the mutation sites at the binding region. The results suggested that BNT162b2 may retain its activity despite mutations and conformational changes in the binding site of the XBB.1.5. The findings of this study shed light on the importance and usability of the current BNT162b2 vaccine for XBB.1.5 and future variants of concern.

A-294 Duplicate Testing of Samples Suspected of SARS-CoV-2 Infection Could Prevent Misdiagnosis of Covid-19

Abstract Background There is no doubt that the whole world has been shaken by the SARS-CoV-2 pandemic, which has affected both global health and the global economy. At the same time the importance of molecular methods for the accurate diagnosis of respiratory infections has been reinforced together with the need of testing methodologies that minimize the risk of misleading results. During the last three years of the pandemic, SARS-CoV-2 exhibited a tremendous adaptation capability through numerous mutations, leading to the appearance of the well-known Variants of Concern (VOCs) responsible of increased transmission rates. Therefore, the development of molecular methods capable of detecting all variants has become a challenge. To overcome this, potential genetic targets with low mutation rates have been identified, including ORF1ab, N gene, S gene and E gene. While Real-time PCR based detection assays of viral genomes are very accurate, testing naso/oropharyngeal samples using singlet analysis does not guarantee the error free detection of true positive results for SARS-CoV-2 infections. Furthermore, it has been documented that the probability of a false-negative testing results is influenced by a number of variables . Therefore, testing protocol adaptations, such as replicate testing, has been shown to efficiently reduce the probability of missing SARS-CoV-2 positive cases. The pilot study presented here investigates the outcome of testing 10 014 nasopharyngeal samples collected from patients with a suspected SARS-CoV-2 infection using two separate detection kits. In this study the error rate of single vs duplicate testing is discussed. Methods 10 014 nasopharyngeal swabs, collected from three different U.K. hospital trusts and Kent based care homes, were tested at the North Kent Pathology Service (NKPS). Each swab collected was placed in sterile transport media and stored at 4°C prior to viral genome isolation using the HigherPurity™ Viral RNA extraction kit. All collected specimens were processed within 24 h from collection. Total RNA isolated was immediately analyzed using two commercial CE-IVD kits: Vitassay qPCR SARS-CoV-2 and Primerdesign™ LTD, Coronavirus (COVID-19) Genesig Real-Time PCR assay. All samples were tested in duplicate. Results Following the testing and subsequent analysis, 491 samples (4.9%) were detected positive for SARS-CoV-2 using both assay kits. Of these, 302 samples (61.5%) were reported as duplicate positive (on both replicate 1 and 2) whereas 189 samples (38.5%) were detected positive on either replicate 1 or 2. In particular, 85 (17.3%) were detected positive on replicate 1 and 104 (21.2%) were detected positive on replicate 2. Conclusions Approximately 19% of tested individuals were detected as SARS-CoV-2 positive based on a positive Real-time PCR result in one of the two reactions. This percentage represents the potential SARS-CoV-2 infections that can be missed when a single reaction Real-time PCR testing is employed for infection detection in the wider population, and equates to 940 individuals out of 100 000 potentially being falsely confirmed as SARS-CoV-2 negative The authors believe that in the presence of fast transmitting variants this is a significant number of false negative tests and should be taken into consideration when testing protocols are developed and disease modelling is employed.