Low Transmission Rate Research Articles

Molecular Epidemiology of SARS-CoV-2 in Greece Reveals Low Rates of Onward Virus Transmission after Lifting of Travel Restrictions Based on Risk Assessment during Summer 2020.

ABSTRACTThe novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spread rapidly during the first months of 2020 and continues to expand in multiple areas across the globe. Molecular epidemiology has provided an added value to traditional public health tools by identifying SARS-CoV-2 clusters or providing evidence that clusters based on virus sequences and contact tracing are highly concordant. Our aim was to infer the levels of virus importation and to estimate the impact of public health measures related to travel restrictions to local transmission in Greece. Our phylogenetic and phylogeographic analyses included 389 full-genome SARS-CoV-2 sequences collected during the first 7 months of the pandemic in Greece and a random collection in five replicates of 3,000 sequences sampled globally, as well as the best hits to our data set identified by BLAST. Phylogenetic trees were reconstructed by the maximum likelihood method, and the putative source of SARS-CoV-2 infections was inferred by phylogeographic analysis. Phylogenetic analyses revealed the presence of 89 genetically distinct viruses identified as independent introductions into Greece. The proportion of imported strains was 41%, 11.5%, and 8.8% during the three periods of sampling, namely, March (no travel restrictions), April to June (strict travel restrictions), and July to September (lifting of travel restrictions based on thorough risk assessment), respectively. The results of phylogeographic analysis were confirmed by a Bayesian approach. Our findings reveal low levels of onward transmission from imported cases during summer and underscore the importance of targeted public health measures that can increase the safety of international travel during a pandemic.IMPORTANCE Our study based on current state-of-the-art molecular epidemiology methods suggests that virus screening and public health measures after the lifting of travel restrictions prevented SARS-CoV-2 onward transmission from imported cases during summer 2020 in Greece. These findings provide important data on the efficacy of targeted public health measures and have important implications regarding the safety of international travel during a pandemic. Our results can provide a roadmap about prevention policy in the future regarding the reopening of borders in the presence of differences in vaccination coverage, the circulation of the virus, and the presence of newly emergent variants across the globe.

Analysis of Anti-CMV T-Cell Immunity and CMV Reactivation after Allogeneic Hematopoietic Cell Transplantation

Introduction. Positive anti-CMV serology is indicative of a pre-existing immunologic response against CMV. CMV reactivation and disease are significant complications after alloHCT. We studied anti-CMV T-cell immunity and its effects on CMV reactivation and disease relapse after alloHCT using anti-CMV specific T-cell multimers and CMV antigenemia. Identification of factors which contribute to CMV reactivation and disease relapse could lead to novel interventions to decrease the morbidity and mortality of alloHCT.Methods. This was a retrospective analysis of prospectively gathered clinical and correlative laboratory data. We quantified anti-CMV T cells in recipients before alloHCT and at days 30 and 100 after alloHCT using CMV specific MHC multimers (Dextramers, Immudex, Denmark). Multimers consist of dextran polymers conjugated to optimized numbers of MHC-CMV peptide complexes and fluorochrome molecules which bind with high avidity to CMV specific T-cells. Dextramers were restricted to HLA-A01, -A02, -A03, -A24, -B07, -B08, and -B35, and were informative in 93% of our predominantly White (97%) population. CMV reactivation was determined with CMV antigenemia based on once weekly testing after WBC recovery until day 100 and as clinically indicated at subsequent follow-up visits. CMV reactivation was defined as the presence of CMV antigen in ≥2/50,000 leukocytes on a single occasion or ≥1/100,000 leukocytes twice consecutively ± anti-CMV therapy, or ≥1/100,000 cells on a single occasion + anti-CMV therapy. Absence of CMV reactivation was defined as CMV antigen in 0-1/100,000 cells without anti-CMV therapy. CMV reactivation was treated preemptively with ganciclovir or foscarnet.Results. 327 consecutive patients received a 10/10 HLA matched unrelated or 6/6 HLA matched related T-cell replete first alloHCT between 2/1/2008 and 12/31/2016, had informative HLA for multimer testing, and had a pre-alloHCT and at least one post-alloHCT multimer test (Table). Recipients (R) and donors (D) who were both negative for CMV by serology (R-/D-) did not reactivate CMV at any time post-alloHCT. Only 6% of R-/D+ reactivated CMV post-alloHCT at a median day+40 indicating a low rate of CMV transmission from donor to recipient. 52% of R+/D- pairs reactivated CMV at a median 40 days post alloHCT compared to 42% of R+/D+ pairs at a median 42 days post alloHCT. Quantitative anti-CMV T cell immunity was analyzed at 1, 3, 5 and 10 cells/µL. Reconstitution of anti-CMV T cell immunity at any level at day+30 post alloHCT was not associated with CMV reactivation between day +31-100; similar results were seen with anti-CMV T cell immunity at day+100 and CMV reactivation between day+101-365. No differences were seen after stratifying by R+/D+ and R+/D-. Correlation of early (day 0 to+100) CMV reactivation after alloHCT with the cumulative incidence of relapse of the underlying malignancy demonstrated lower relapse rates for patients who had any CMV reactivation (left panel) or >25/50,000 cells positive for CMV (right panel) (Figure).Conclusions. Our findings suggest that early in the course of T cell replete HLA-matched alloHCT, multimer based measurements of anti-CMV T cells do not predict for protective immunity against CMV. The incidence of disease relapse may be lower after CMV reactivation. Further analysis according to conditioning regimen intensity, GvHD incidence, and lymphocyte chimerism to confirm these findings is underway. [Display omitted] DisclosuresChen:Immudex: Research Funding. Brix:Immudex: Employment. Wallace:Immudex: Research Funding.

Layer-by-Layer Assembled Nano-Composite Multilayer Gas Barrier Film Manufactured with Stretchable Substrate

Most gas barrier films produce cracks that lead to a significant loss of gas barrier integrity when strain is applied. In order to fabricate stretchable gas barrier films with low water permeability and high endurance after stretching, we used polydiallydimethylammonium (PDDA) mixed with graphene oxide (GO) and poly (vinyl alcohol) (PVA) mixed with montmorillonite (MMT). These films were manufactured by layer-by-layer assembly on an Ecoflex/polydimethylsiloxane (PDMS) substrate with pre-strain applied. A total of 30 layers of PDDA (GO)/PVA (MMT) coated on the substrate exhibited a low water vapor transmission rate of 2.5 × 10−2 g/m2 day after 100 cycles of stretching (30% strain). In addition, they exhibited a high light transmittance of 86.54%. Thus, the prepared stretchable gas barrier film has potential applications as a barrier film in transparent and stretchable electronic devices.

Performance analysis of short-packet communications with incremental relaying

In the fifth generation (5G) cellular system, short-packet communication is a key enabler to support critical applications, i.e., ultra-reliable low-latency communications (URLLCs), where finite block-length codewords are adopted. However, the short-packet communication suffers from a higher decoding error rate and has a lower transmission rate than the Shannon channel capacity. To improve both the reception reliability and the transmission efficiency, the incremental relaying (IR) is considered to improve the performance of the short-packet communication. Especially, we investigate an IR scheme for short-packet communications to reduce the transmission delay. To evaluate the system performance, closed-form expressions for the decoding error probability, the throughput and the delay are derived by considering the feedback overhead of IR. Finally, we provide simulation results to verify the accuracy of the theoretical analysis, and also compare the proposed IR scheme with the direct transmission (DT) and conventional relaying transmission (RT) schemes. Simulation results verify the effectiveness of the proposed IR scheme for the short-packet communication.

Coded Caching Schemes With Linear Subpacketizations

In coded caching system we prefer to design a coded caching scheme with low subpacketization and small transmission rate (i.e., the low implementation complexity and the efficient transmission during the peak traffic times). Placement delivery arrays (PDA) can be used to design code caching schemes. In this article we propose a framework of constructing PDAs via Hamming distance. As an application, two classes of coded caching schemes with linear subpacketizations and small transmission rates are obtained.

Transmission dynamics of Staphylococcus aureus and Streptococcus agalactiae in a Dutch dairy herd using an automatic milking system

Staphylococcus aureus and Streptococcus agalactiae are important contagious mastitis pathogens and are considered to mainly transmit between cows through the milking machine. Controlling contagious mastitis on dairy farms requires a reduction of the transmission rate or the duration of intramammary infections (IMI), or both. These parameters may differ in dairy herds milked with an automatic milking system (AMS) as compared to those milked with a conventional milking system (CMS). The aims of this prospective longitudinal study were to estimate the transmission rate, the median duration of IMI and the basic reproduction number (R0) of Staph. aureus and Strep. agalactiae in a Dutch AMS herd. Bacteriological cultures of quarter milk samples were collected every 2 wks. Using 3 different definitions of IMI, we estimated the transmission rate for Staph. aureus to be within the range of 0.002 (95 % CI: 0−0.005) quarter-day−1 to 0.019 (95 % CI: 0.010−0.032) quarter-day−1, and for Strep. agalactiae of 0.007 (95 % CI: 0.005−0.010) quarter-day−1 to 0.019 (95 % CI: 0.011−0.032) quarter-day−1, the median duration of chronic IMI at 95 (95 % CI: 72−125) days for Staph. aureus and at 86 (95 % CI: 67−111) days for Strep. agalactiae, and the R0 between 0.16 (95 % CI: 0.05−0.27) and 0.34 (95 % CI: 0.20−0.48) for Staph. aureus, and between 0.64 (95 % CI: 0.41−0.87) and 0.68 (95 % CI: 0.48−0.88) for Strep. agalactiae.Transmission of these two contagious pathogens in this herd was limited and theoretically the IMI would not sustain, given that R0 of both pathogens was lower than 1. The estimated transmission rate of Staph. aureus in this AMS herd was found to be comparable to those described for CMS herds, while for Strep. agalactiae, it was slightly higher than in CMS herds. The duration of Staph. aureus IMI was in line with results from CMS farms, while the duration of Strep. agalactiae was lower than what has been described in CMS herds. The R0 of these contagious pathogens was found to be lower than the estimates in CMS herds. Our study suggests that the transmission rate of these two contagious pathogens in this AMS herd were comparable to what has been reported about well-performing CMS herds that have a low rate of transmission.

Zika vaccines: can we solve one problem without creating another one?

Since 2015, the emergence of epidemic Zika virus transmission have been linked to unparalleled reports of serious neurological disorders and devastating birth defects such as microcephaly and other congenital malformations.1,2 Despite low transmission rates in the past 3 years, the emergence of new Zika outbreaks remains a looming threat. Of particular concern to health authorities worldwide is the possibility of multiple flavivirus outbreaks, as Zika became endemic in the same regions as dengue viruses.

Deep Learning Based Object Detection Combined with Internet of Things for Remote Surveillance

Object detection is the key process in any video surveillance application. In case of remote surveillance, it is a necessity to accurately detect the target and transmit the detected data rapidly to main station so that further actions can be taken. This paper concentrates on a framework which uses deep neural network and Internet of Things for target detection and transferring detected information to the cloud at low transmission rates. The detection framework is based on combination of YOLO-Lite which is a simpler version of you only look once (YOLO) detector and spatial pyramid pooling (SPP). When trained on COCO dataset, YOLO-Lite + SPP model runs at a speed of 40 fps with mAP of 35.7% on non-GPU platform. Performance of the same has been analyzed on PASCAL VOC, COCO, TB-50 and TB-100 dataset. On GPU based platform, precision and recall values of 89.79% and 91.67% has been achieved with processing speed of 218 fps. ThingSpeak platform has been used for data reception on cloud. Results in real-time are also demonstrated which proves the efficiency of the anticipated framework and also confirms its suitability for remote video surveillance.

A novel scalable network architecture for the evolution of robot swarm networks with dual connectivity application in control-data plane

The swarm robot network is the widely used wireless communication technology, and significantly, it has higher uplink and downlink throughput than the conventional communication networks. Apart from the appreciable advantages, there are various challenges like minimized data retention rate, low data transmission rate, countless handovers over a short time, and a short transmission range due to higher data transmission usage. To resolve these challenges, Scalable Network Architecture with Dual Connectivity Application (SN-DCA) in control and data plane is proposed to improve data retention rates and minimize network usage by controlling unwanted access in the distributive clouds during transmission. Here, Two-stage control data plane splitting (TSCDP) is introduced to enhance network usage by optimizing unwanted access. It further improves the data retention rate during transmission. The analytical performance of the proposed techniques has been validated computationally and examined through simulation studies. The Simulation results show that these techniques achieve a higher performance ratio in the network with a minimum transmission delay and a high data retention rate.

Changes in Emergency Department Activity and the First COVID-19 Lockdown: A Cross-sectional Study.

IntroductionEmergency department (ED) attendances fell across the UK after the ‘lockdown’ introduced on 23rd March 2020 to limit the spread of coronavirus disease 2019 (COVID-19). We hypothesised that reductions would vary by patient age and disease type. We examined pre- and in-lockdown ED attendances for two COVID-19 unrelated diagnoses: one likely to be affected by lockdown measures (gastroenteritis), and one likely to be unaffected (appendicitis).MethodsWe conducted a retrospective cross-sectional study across two EDs in one London hospital Trust. We compared all adult and paediatric ED attendances, before (January 2020) and during lockdown (March/April 2020). Key patient demographics, method of arrival, and discharge location were compared. We used Systemised Nomenclature of Medicine codes to define attendances for gastroenteritis and appendicitis.ResultsED attendances fell from 1129 per day before lockdown to 584 in lockdown, 51.7% of pre-lockdown rates. In-lockdown attendances were lowest for under-18s (16.0% of pre-lockdown). The proportion of patients admitted to hospital increased from 17.3% to 24.0%, and the proportion admitted to intensive care increased fourfold. Attendances for gastroenteritis fell from 511 to 103, 20.2% of pre-lockdown rates. Attendances for appendicitis also decreased, from 144 to 41, 28.5% of pre-lockdown rates.ConclusionED attendances fell substantially following lockdown implementation. The biggest reduction was for under-18s. We observed reductions in attendances for gastroenteritis and appendicitis. This may reflect lower rates of infectious disease transmission, although the fall in appendicitis-related attendances suggests that behavioural factors were also important. Larger studies are urgently needed to understand changing patterns of ED use and access to emergency care during the coronavirus 2019 pandemic.

Performance investigation of spectral-efficient high-speed inter-satellite optical wireless communication link incorporating polarization division multiplexing

Space information transmission links are crucial for covering the entire globe for communication purposes. The traditional microwave frequency-based satellite communication links have high latency and low information transmission rates. In the last few years, inter-satellite optical wireless communication (IsOWC) technology has evolved significantly as a result of its numerous benefits like wide channel bandwidth, high-speed links, and low mass and power requirements. Different research groups have proposed IsOWC links based on conventional on–off modulation schemes for transmitting 10 Gbps data between satellites separated in space. But the future generation transmission links require higher spectral efficiency and data rates with longer transmission reach. In this research, a novel single-channel spectrum-efficient 160 Gbps polarization division multiplexing-based IsOWC link is investigated for long communication range transmission. In this design, coherent detection technique is employed to mitigate the effects of system errors and space turbulence (i.e. pointing errors). A digital signal processing module has been proposed for minimizing the information signal degradation due to space turbulences and to estimate the carrier phase of the signal received. The results show that 160 Gbps information is successfully transmitted over 20,000 km range with an acceptable bit error rate (BER). Also, the influence of different system parameters including pointing error angle, receiver aperture diameter, and additional losses on the signal BER is numerically investigated.

On the Performance of UAV-Aided Content Caching in Small-Cell Networks with Joint Transmission

Unmanned aerial vehicles (UAVs), featured by the high-mobility and high-quality propagation environment, have shown great potential in wireless communication applications. In this paper, a novel UAV-aided small-cell content caching network is proposed and analyzed, where joint transmission (JT) is considered in the dense small-cell networks and mobile UAVs are employed to shorten the serving distance. The system performance is evaluated in terms of the average cache hit probability and the ergodic transmission rate. From the analytical results, we find that (i) the proposed UAV-aided small-cell network shows superior caching performance and, even with a small density of UAVs the system’s cache hit probability, can be improved significantly; (ii) the content’s optimal caching probability to maximize the cache hit probability is proportional to the (K+1)-th root of its request probability, where K is the number of small-cell base stations that serve each user by JT; (iii) caching the most popular content in UAVs may lead to a low transmission rate due to the limited resource offered by the low-density UAVs. Simulation results are presented to validate the theoretical results and the performance gain achieved by the optimal caching strategy.

Rate-Adapted Decentralized Learning Over Wireless Networks

This paper proposes a communication strategy for decentralized learning in wireless systems that employs adaptive modulation and coding capability. The main objective of this work is to address a critical issue in decentralized learning based on the cooperative stochastic gradient descent (C-SGD) over wireless systems: the relationship between the transmission rate and the network density influences the runtime performance of learning. We first present that a dense network topology does not necessarily benefit the iteration performance of learning than a sparse one. However, it tends to degrade the runtime performance because the dense network topology requires a low-rate transmission. Based on these findings, a communication strategy is proposed in which each node optimizes its transmission rate to minimize communication time during the C-SGD under the constraints of network density. We perform numerical simulations of an image classification task under both independent and identically distributed (i.i.d.) and non-i.i.d. settings. The simulation results reveal that the preferred setting for the network density depends on the channel conditions and the biases in the training samples. Furthermore, numerical simulations of an automatic modulation classification task indicate that the preferred setting is almost the same even if the training task is different.

Influence of Two Innovative Packaging Materials on Quality Parameters and Aromatic Fingerprint of Extra-Virgin Olive Oils.

The performance of two innovative packaging materials was investigated on two Sardinian extra-virgin olive oils (Nera di Gonnos and Bosana). In particular, a transparent plastic film loaded with a UV-blocker (packaging B) and a metallized material (packaging C) were compared each other and to brown-amber glass (packaging A). During accelerated shelf-life tests at 40 and 60 °C, the evolution of quality parameters (i.e., acidity, peroxide value, K270, and phenolic content) was monitored, together with the aromatic fingerprint evaluated by electronic nose. Packaging B resulted in the best-performing material in protecting oil from oxidation, due to its lower oxygen transmission rate (0.1 ± 0.02 cm3/m2 24 h) compared to packaging C (0.23 ± 0.04 cm3/m2 24 h). At the end of storage, phenolic reduction was on average 25% for packaging B and 58% for packaging C, and the aromatic fingerprint was better preserved in packaging B. In addition, other factors such as the sanitary status of the olives at harvesting and the storage temperature were demonstrated to have a significant role in the shelf life of packaged extra-virgin olive oil.

Approach for Near-Real-Time Pipe Burst Detection, Localization, and Quantification with Low Data Transmission and Sampling Rates

The purpose of the paper is to present an approach for pipe burst detection, localization, and cross-sectional area quantification based on the changes in the discrete harmonic spectrogram and analysis of damping of fluid transients. The amplitude of each resonance response of the burst-induced transient wave in each analyzed time window in the spectrogram is damped differently because of the presence of the burst. A pressure signal processing algorithm for pipe burst detection and estimation has been developed by the authors to explore this specific type of analysis, in conjunction with a predefined gap between each window. Because the window gap can be set to be equal to the data transmission and sampling rates in the analysis to detect and estimate the burst, it can be applied during real-time data monitoring. Unlike other hydraulic transient-based detection methods, the proposed algorithm only requires the Nyquist frequency of the third resonance response as the data transmission and sampling rates, which are significantly lower than the same quantities in commonly used data acquisition systems. The algorithm has been verified both numerically and experimentally.

The central role of host reproduction in determining the evolution of virulence in spatially structured populations

A substantial body of work has shown that local transmission selects for less acute, ‘prudent’ parasites that have lower virulence and transmission rates. This is because parasite strains with higher transmission rates ‘self-shade’ due to a combination of genetic correlations (self: clustered related parasite strains compete for susceptible individuals) and ecological correlations (shade: infected individuals clustering and blocking transmission). However, the interaction of ecological and genetic correlations alongside higher order ecological effects such as patch extinctions means that spatial evolutionary effects can be nuanced; theory has predicted that a relatively small proportion of local infection can select for highest virulence, such that there is a humped relationship between the degree of local infection and the harm that parasites are selected to cause. Here, we examine the separate roles of the interaction scales of reproduction and infection in the context of different degrees of pathogenic castration in determining virulence evolution outcomes. Our key result is that, as long as there is significant reproduction from infected individuals, local infection always selects for lower virulence, and that the prediction that a small proportion of local infection can select for higher virulence only occurs for highly castrating pathogens. The results emphasize the importance of demography for evolutionary outcomes in spatially structured populations, but also show that the core prediction that parasites are prudent in space is reasonable for the vast majority of host-parasite interactions and mixing patterns in nature.

HOSTED-England's Household Transmission Evaluation Dataset: preliminary findings from a novel passive surveillance system of COVID-19.

BackgroundHousehold transmission of SARS-CoV-2 is an important component of the community spread of the pandemic. Little is known about the factors associated with household transmission, at the level of the case, contact or household, or how these have varied over the course of the pandemic.MethodsThe Household Transmission Evaluation Dataset (HOSTED) is a passive surveillance system linking laboratory-confirmed COVID-19 cases to individuals living in the same household in England. We explored the risk of household transmission according to: age of case and contact, sex, region, deprivation, month and household composition between April and September 2020, building a multivariate model.ResultsIn the period studied, on average, 5.5% of household contacts in England were diagnosed as cases. Household transmission was most common between adult cases and contacts of a similar age. There was some evidence of lower transmission rates to under-16s [adjusted odds ratios (aOR) 0.70, 95% confidence interval (CI) 0.66–0.74). There were clear regional differences, with higher rates of household transmission in the north of England and the Midlands. Less deprived areas had a lower risk of household transmission. After controlling for region, there was no effect of deprivation, but houses of multiple occupancy had lower rates of household transmission [aOR 0.74 (0.66–0.83)].ConclusionsChildren are less likely to acquire SARS-CoV-2 via household transmission, and consequently there was no difference in the risk of transmission in households with children. Households in which cases could isolate effectively, such as houses of multiple occupancy, had lower rates of household transmission. Policies to support the effective isolation of cases from their household contacts could lower the level of household transmission.

Prevalence and associated risk factors of malaria infection among pregnant women attending antenatal clinic in Yola North, Adamawa State, Nigeria

This study determined the prevalence and associated risk factors of malaria infection among pregnant women attending antenatal clinic in Yola North, Adamawa State, Nigeria, between December 2017 and April 2018. Both direct microscopy and rapid diagnostic test were employed in this study to establish infection. Structured questionnaires were used to collect information from the participants. The study showed that 63 pregnant women were positive for malaria infection out of the 270 sampled. Overall malaria prevalence of 23.3% was recorded during this study. There was no significant association between malaria infection and the clinics sampled (p>0.05). Results have shown that the prevalence was relatively low, and this could be attributed to low transmission rate of malaria during dry season in Adamawa State. In relation to parity, prevalence of malaria were; primigravidae (21.6%), secundravidae (20.0%) and multigravidae (26.7%). Similarly, in relation to gestational age prevalence was first trimester (27.9%), second trimester (25.0%) and thirdtrimester (20.0%). There were no significant associations between malaria infection, parity and gestational age (p>0.05). The age-group 38 ≥ years had highest prevalence while 15-23 years had least. There was no significant association between malaria infection, educational level and occupation (p>0.05). Relating to the participants occupation, prevalence of malaria was reported as 30.0, 22.9 and 23.5% for civil servants, unemployed and business respectively. It is therefore recommended that early attendance and utilization of focused antenatal care services by all pregnant women will reduce the risk of malaria in pregnancy.
 Keywords: Risk factors; malaria; pregnant women; antenatal; Yola North.

Modeling of COVID-19 with limited public health resources: a comparative study of three most affected countries

COVID-19 has become a deadly pandemic in the recent times claiming millions of lives worldwide in a grievous manner. Most of the countries in the world have limited number of medical resources (hospitals, beds, ventilators, etc.), and in the case of large outbreak, it becomes very difficult to provide treatment to every infected individual. In this study, we propound a mathematical model where we classify the infected into two subcategories—asymptomatic and symptomatic. This model further accounts for the effect of limited medical resource for infected people and using face masks in combating the pandemic. Focusing on these aspects, we analyze the model and exploit the available data for assessing the pattern in three most affected countries, namely USA, India and Brazil. The developed model is calibrated to fit data for these three countries and estimate the transmission rate of symptomatic, asymptomatic individuals. The rate at which the individuals who are quarantined recover is estimated as well. Along with these estimations, a comparative study based on the basic reproduction number estimated for the three countries is presented. Standard methods of sensitivity analysis are performed to analyze the ways in which basic reproduction number is impacted upon due to changes in different parameters of the model. Further, we obtain disease-free equilibrium and endemic equilibrium of the model. It is observed that backward bifurcation occurs if the capacity of treatment is small and bistable equilibria are shown that makes the system more sensitive to the initial conditions. Sufficient conditions for the local asymptomatic stability of the endemic equilibrium and disease-free equilibrium of the system are obtained. The results of this study imply that to curb the severity of the increasing cases of the disease in these countries, effective strategies to control disease spread should be implemented so that the basic reproduction number can be decreased below the threshold value which is certainly less than unity. The use of protective masks in public is shown to be an important preventive measure to lower disease transmission rate. Also, the quantity of medical resources should increase so that every infected person can get better treatment.

A Janus compatible software-defined underwater acoustic multiple-input multiple-output modem

This article describes the implementation of a multiple-input multiple-output acoustic communication link in shallow water conditions to enable a software-defined acoustic modem with a maximum transmission rate of 20 kbps in a 5-kHz bandwidth. The reliability improvement of a low-complexity Alamouti space–time block code is evaluated to improve the diversity in a high-rate transmission mode using single carrier modulation, as well as in a low-rate transmission mode relying on continuous-phase frequency-shift keying. Using measurements in realistic subsea conditions, the effect of the spatial channel correlation is demonstrated. It is found that for the space–time block code/continuous-phase frequency-shift keying, the spatial diversity is significantly degraded due to the high spatial correlation. In contrast, for the high-mode transmission rate, space–time block code with single carrier modulation offers a bit error rate improvement by a factor over hundred, in comparison to a single transmit element, demonstrating that the multiple-input multiple-output optimal code depends on the software-defined acoustic modem transmission mode.