SARS-CoV-2 aerosol transmission in schools: the effectiveness of different interventions

Background: Indoor aerosol transmission of SARS-CoV-2 has been widely recognized, especially in schools where children remain in close proximity and largely unvaccinated. Measures such as strategic natural ventilation and high efficiency particulate air (HEPA) filtration remain poorly implemented and mask mandates are often progressively lifted as vaccination rollout is enhanced. Methods: We adapted a previously developed aerosol transmission model to study the effect of interventions (natural ventilation, face masks, HEPA filtration, and their combinations) on the concentration of virus particles in a classroom of 160 m3 containing one infectious individual. The cumulative dose of viruses absorbed by exposed occupants was calculated. Results: The most effective single intervention was natural ventilation through the full opening of six windows all day during the winter (14-fold decrease in cumulative dose), followed by the universal use of surgical face masks (8-fold decrease). In the spring/summer, natural ventilation was only effective (≥ 2-fold decrease) when windows were fully open all day. In the winter, partly opening two windows all day or fully opening six windows at the end of each class was effective as well (≥ 2-fold decrease). Opening windows during yard and lunch breaks only had minimal effect (≤ 1.2-fold decrease). One HEPA filter was as effective as two windows partly open all day during the winter (2.5-fold decrease) while two filters were more effective (4-fold decrease). Combined interventions (i.e., natural ventilation, masks, and HEPA filtration) were the most effective (≥ 30-fold decrease). Combined interventions remained highly effective in the presence of a super-spreader. Conclusions: Natural ventilation, face masks, and HEPA filtration are effective interventions to reduce SARS-CoV-2 aerosol transmission. These measures should be combined and complemented by additional interventions (e.g., physical distancing, hygiene, testing, contact tracing, and vaccination) to maximize benefit.

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Smart DRA for beam width and orientation control

Frequenz ◽

10.1515/freq-2020-0013 ◽

2020 ◽

Vol 74 (11-12) ◽

pp. 383-392

Author(s):

Rajveer S. Yaduvanshi ◽

Richa Gupta ◽

Saurabh Katiyar

Keyword(s):

Radiation Pattern ◽

High Efficiency ◽

Beam Width ◽

Beam Control ◽

Design Flexibility ◽

Compact Size ◽

Close Proximity ◽

Cellular Communication Network ◽

Arc Shape ◽

Broadside Radiation

AbstractSmartdielectric resonator antenna (DRA) having beam control mechanism is anew area to be explored by antenna researchers. Proposed new geometry DRA has low loss, design flexibility, high efficiency, compact size and desired radiated beam control. Developing beam control in new geometry DRAs is investigated for the first time in this letter. Unique technique for beam control and beam width control is proposed using pit top and mount top DRA. Gain is controlled from 5.0 to 9.98 dBi and beam is controlled from ±30° to ±70° in broadside radiation pattern. U shape pit DRA has maximum directive gain of 9.98 dBi and efficiency 98% at 5.8 GHz frequency. Measured and simulated results of radiation pattern and reflection coefficient are found to be in close proximity. Hardware of U shape pit top DRA, mount top DRA, left side arc top DRA, right side arc shape top DRA is developed and investigated. Mobile and cellular communication network need wide coverage, hence large beam width is required. Narrowing of beam width at higher order mode is also achieved.

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Establishment, contagiousness, and initial spread of SARS-CoV-2 in Canada

FACETS ◽

10.1139/facets-2020-0055 ◽

2021 ◽

Vol 6 (1) ◽

pp. 180-194

Author(s):

Martin Krkošek ◽

Madeline Jarvis-Cross ◽

Kiran Wadhawan ◽

Isha Berry ◽

Jean-Paul R. Soucy ◽

...

Keyword(s):

Latent Period ◽

Bayesian Framework ◽

Contact Tracing ◽

Transmission Model ◽

Infectious Period ◽

Median Reduction ◽

Community Transmission

This study empirically quantifies dynamics of SARS-CoV-2 establishment and early spread in Canada. We developed a transmission model that was simulation tested and fitted in a Bayesian framework to timeseries of new cases per day prior to physical distancing interventions. A hierarchical version was fitted to all provinces simultaneously to obtain average estimates for Canada. Across scenarios of a latent period of 2–4 d and an infectious period of 5–9 d, the R0 estimate for Canada ranges from a minimum of 3.0 (95% CI: 2.3–3.9) to a maximum of 5.3 (95% CI: 3.9–7.1). Among provinces, the estimated commencement of community transmission ranged from 3 d before to 50 d after the first reported case and from 2 to 25 d before the first reports of community transmission. Among parameter scenarios and provinces, the median reduction in transmission needed to obtain R0 < 1 ranged from 46% (95% CI: 43%–48%) to 89% (95% CI: 88%–90%). Our results indicate that local epidemics of SARS-CoV-2 in Canada entail high levels of stochasticity, contagiousness, and observation delay, which facilitates rapid undetected spread and requires comprehensive testing and contact tracing for its containment.

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TraceTogether: Pandemic Response, Democracy, and Technology

East Asian Science Technology and Society ◽

10.1215/18752160-8698301 ◽

2020 ◽

Vol 14 (3) ◽

pp. 523-532 ◽

Cited By ~ 4

Author(s):

Hallam Stevens ◽

Monamie Bhadra Haines

Keyword(s):

Citizen Science ◽

Social Trust ◽

Public Support ◽

Contact Tracing ◽

Democratic Participation ◽

Government Power ◽

Power And Control ◽

Close Proximity ◽

Pandemic Response ◽

And Control

Abstract On 20 March 2020, in the midst of the COVID-19 pandemic, the Singapore government released a new app called TraceTogether. Developed by the Ministry of Health, SG United, and GovTech Singapore, the app uses the Bluetooth capability of smartphones to store information about other smartphones that have come into close proximity with your own. These data facilitate the government’s process of “contact tracing” through which they track those who have potentially come into contact with the virus and place them in quarantine. This essay attempts to understand what kinds of citizens and civic behavior might be brought into being by this technology. By examining the workings and affordances of the TraceTogether app in detail, the authors argue that its peer-to-peer and open-source technology features mobilize the rhetorics and ideals of citizens science and democratic participation. However, by deploying these within a context that centralizes data, the app turns ideals born of dissent and protest on their head, using them to build trust not within a community but rather in government power and control. Rather than building social trust, TraceTogether becomes a technological substitute for it. The significant public support for TraceTogether shows both the possibilities and limitations of citizen science in less liberal political contexts and circumstances.

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Changes in contact patterns shape the dynamics of the COVID-19 outbreak in China

Science ◽

10.1126/science.abb8001 ◽

2020 ◽

Vol 368 (6498) ◽

pp. 1481-1486 ◽

Cited By ~ 202

Author(s):

Juanjuan Zhang ◽

Maria Litvinova ◽

Yuxia Liang ◽

Yan Wang ◽

Wei Wang ◽

...

Keyword(s):

Confidence Interval ◽

Odds Ratio ◽

School Closure ◽

Hunan Province ◽

Contact Tracing ◽

Transmission Model ◽

Social Distancing ◽

Susceptibility To Infection ◽

Contact Patterns ◽

The Impact

Intense nonpharmaceutical interventions were put in place in China to stop transmission of the novel coronavirus disease 2019 (COVID-19). As transmission intensifies in other countries, the interplay between age, contact patterns, social distancing, susceptibility to infection, and COVID-19 dynamics remains unclear. To answer these questions, we analyze contact survey data for Wuhan and Shanghai before and during the outbreak and contact-tracing information from Hunan province. Daily contacts were reduced seven- to eightfold during the COVID-19 social distancing period, with most interactions restricted to the household. We find that children 0 to 14 years of age are less susceptible to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection than adults 15 to 64 years of age (odds ratio 0.34, 95% confidence interval 0.24 to 0.49), whereas individuals more than 65 years of age are more susceptible to infection (odds ratio 1.47, 95% confidence interval 1.12 to 1.92). Based on these data, we built a transmission model to study the impact of social distancing and school closure on transmission. We find that social distancing alone, as implemented in China during the outbreak, is sufficient to control COVID-19. Although proactive school closures cannot interrupt transmission on their own, they can reduce peak incidence by 40 to 60% and delay the epidemic.

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Low-Cost High-Efficiency Joint Training Program

Prehospital and Disaster Medicine ◽

10.1017/s1049023x19003273 ◽

2019 ◽

Vol 34 (s1) ◽

pp. s147-s147

Author(s):

Emmanuelle St-Arnaud

Keyword(s):

High Efficiency ◽

Emergency Services ◽

Low Cost ◽

Exercise Program ◽

First Year ◽

Fire Departments ◽

Minimal Impact ◽

Effective Interventions ◽

Major Incidents ◽

Key Issues

Introduction:As the second largest metropolitan area in Canada, Montréal has its share of risks for disasters and major incidents. In such events, the interoperability of emergency services is critical to effective interventions. As the emergency medical service (EMS) for the cities of Montréal and Laval, the Urgences-santé Corporation (USC) has close ties with several emergency partners on the territory, including police and fire departments. These different organizations have joined forces to develop a tabletop exercise program (TEP) to train operational managers to initiate a better-coordinated response on joint interventions.Aim:The TEP was designed to enhance interoperability in the field by improving communication and the understanding of the roles, responsibilities, methods of coordination and decision-making in each of the organizations involved. The aim is for all of USC’s operational managers to participate in at least one exercise of the TEP within the first year of the program.Methods:Selection criteria were established to gather, for each exercise, managers that are likely to work with one another on a real intervention. The TEP was also designed in such a way that its implementation would require few resources and yield minimal impact on regular operations.Results:After four pilot exercises to fine-tune the approach, the program was launched on October 5, 2018. We have now run eight exercises, each involving one or more USC supervisor. The response has been very favorable from the participants as well as their directors.Discussion:In the short term, the TEP helps managers understand their counterparts’ key issues, and has already yielded improvements in our joint interventions. In the longer term, the program will help identify specific training needs to better equip responders.

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Cost-effectiveness of influenza control measures: a dynamic transmission model-based analysis

Epidemiology and Infection ◽

10.1017/s0950268813000423 ◽

2013 ◽

Vol 141 (12) ◽

pp. 2581-2594 ◽

Cited By ~ 7

Author(s):

S.-C. CHEN ◽

C.-M. LIAO

Keyword(s):

Cost Effectiveness ◽

Natural Ventilation ◽

Seasonal Influenza ◽

School Setting ◽

Control Measures ◽

Transmission Model ◽

Model Based ◽

Dynamic Transmission Model ◽

Influenza Transmission ◽

The Cost

SUMMARYWe investigated the cost-effectiveness of different influenza control strategies in a school setting in Taiwan. A susceptible-exposure-infected-recovery (SEIR) model was used to simulate influenza transmission and we used a basic reproduction number (R0)–asymptomatic proportion (θ) control scheme to develop a cost-effectiveness model. Based on our dynamic transmission model and economic evaluation, this study indicated that the optimal cost-effective strategy for all modelling scenarios was a combination of natural ventilation and respiratory masking. The estimated costs were US$10/year per person in winter for one kindergarten student. The cost for hand washing was estimated to be US$32/year per person, which was much lower than that of isolation (US$55/year per person) and vaccination (US$86/year per person) in containing seasonal influenza. Transmission model-based, cost-effectiveness analysis can be a useful tool for providing insight into the impacts of economic factors and health benefits on certain strategies for controlling seasonal influenza.

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Uncertainty quantification and sensitivity analysis of COVID-19 exit strategies in an individual-based transmission model

10.1101/2021.03.24.21254218 ◽

2021 ◽

Author(s):

Federica Gugole ◽

Luc E. Coffeng ◽

Wouter Edeling ◽

Benjamin Sanderse ◽

Sake J. de Vlas ◽

...

Keyword(s):

Sensitivity Analysis ◽

Uncertainty Quantification ◽

Computational Models ◽

Small Region ◽

Contact Tracing ◽

Transmission Model ◽

Policy Makers ◽

Distribution Of Values ◽

Exit Strategies ◽

Key Indicators

Many countries are currently dealing with the COVID-19 epidemic and are searching for an exit strategy such that life in society can return to normal. To support this search, computational models are used to predict the spread of the virus and to assess the efficacy of policy measures before actual implementation. The model output has to be interpreted carefully though, as computational models are subject to uncertainties. These can stem from, e.g., limited knowledge about input parameters values or from the intrinsic stochastic nature of some computational models. They lead to uncertainties in the model predictions, raising the question what distribution of values the model produces for key indicators of the severity of the epidemic. Here we show how to tackle this question using techniques for uncertainty quantification and sensitivity analysis. We assess the uncertainties and sensitivities of four exit strategies implemented in an agent-based transmission model with geographical stratification. The exit strategies are termed Flattening the Curve, Contact Tracing, Intermittent Lockdown and Phased Opening. We consider two key indicators of the ability of exit strategies to avoid catastrophic health care overload: the maximum number of prevalent cases in intensive care (IC), and the total number of IC patient-days in excess of IC bed capacity. Our results show that uncertainties not directly related to the exit strategies are secondary, although they should still be considered in comprehensive analysis intended to inform policy makers. The sensitivity analysis discloses the crucial role of the intervention uptake by the population and of the capability to trace infected individuals. Finally, we explore the existence of a safe operating space. For Intermittent Lockdown we find only a small region in the model parameter space where the key indicators of the model stay within safe bounds, whereas this region is larger for the other exit strategies.

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Dithering Analysis in an Orthogonal Frequency Division Multiplexing-Radio over Fiber Link

International Journal of Electrical and Computer Engineering (IJECE) ◽

10.11591/ijece.v6i3.pp1112-1121 ◽

2016 ◽

Vol 6 (3) ◽

pp. 1112

Author(s):

Fakhriy Hario P ◽

Adhi Susanto ◽

I Wayan Mustika ◽

Sevia M Idrus ◽

Sholeh Hadi P

Keyword(s):

Optical Fibers ◽

Orthogonal Frequency Division Multiplexing ◽

High Efficiency ◽

Power Level ◽

High Capacity ◽

Coherent Detection ◽

Frequency Division ◽

Close Proximity ◽

Qam Modulation ◽

Fiber Link

Nonlinearity is one major problem broadband communication faced on utilizing the high capacity of optical fibers. That is due to scattering phenomenon, which results in the deviations of wavelengths and energies. The dithering method is applied in the attempt to reduce those scatterings. In this paper, we propose the performance of a dithering technique based new system OFDM-RoF using two modulator scheme and coherent detection to alleviate the characteristics nonlinearity applied on the system. The dithering technique inputs signal externally to the signal processing systems to eliminate the effects of nonlinearity. Here, we report the performance of a dithering technique based on the OFDM-RoF, the results our experiment showed that the applied dithering with 16 QAM modulation can make the system more reliable and increases the power level 1.55% with 193.1 THz, 2% with 100 THz and 1.99% ~ 200 THz, the best condition are with fd < fc. However, all condition close proximity in the parameters OLP (optical launch power), BER and SER measurement. The result demonstrated a high efficiency and good power in which the OLP operated 6.396 dBm / 4.361 E-3 W~fd 200 THz, 3.578 dBm / 2.279 E-3 W~fd 193.1 THz and 6.420 dBm / 4.3384 E-3 W~100 THz. The best BER value is achieved at 0.33 and SER 0.78 at 5 km~fd 100 THz, 0.33 and 0.768 for 10 km~fd 193.1 THz, 0.478 and 0.92 for 50 km~fd 193.1 THz.

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Temporary Immunity and Multiple Waves of COVID-19

10.1101/2020.07.01.20144394 ◽

2020 ◽

Author(s):

B Shayak ◽

Mohit M Sharma ◽

Anoop Misra

Keyword(s):

Mathematical Modeling ◽

Contact Tracing ◽

Time Interval ◽

Current Time ◽

Intervention Level ◽

Effective Interventions ◽

One Year ◽

Parameter Values ◽

Threshold Duration

ABSTRACTIn this work we use mathematical modeling to describe the potential phenomena which may occur if immunity to COVID-19 lasts for a finite time instead of being permanent, i.e. if a recovered COVID-19 patient may again become susceptible to the virus after a given time interval following his/her recovery. Whether this really happens or not is unknown at the current time. If it does happen, then we find that for certain combinations of parameter values (social mobility, contact tracing, immunity threshold duration etc), the disease can keep recurring in wave after wave of outbreaks, with a periodicity approximately equal to twice the immunity threshold. Such cyclical attacks can be prevented trivially if public health interventions are strong enough to contain the disease outright. Of greater interest is the finding that should such effective interventions not prove possible, then also the second and subsequent waves can be forestalled by a consciously relaxed intervention level which finishes off the first wave before the immunity threshold is breached. Such an approach leads to higher case counts in the immediate term but significantly lower counts in the long term as well as a drastically shortened overall course of the epidemic.As we write this, there are more than 1,00,00,000 cases (at least, detected cases) and more than 5,00,000 deaths due to COVID-19 all over the globe. The unknowns surrounding this disease outnumber the knowns by orders of magnitude. One of these unknowns is how long does immunity last i.e., once a person recovers from COVID-19 infection, how long does s/he remain insusceptible to a fresh infection. Most modeling studies assume lifetime immunity, or at least sufficiently prolonged immunity as to last until the outbreak is completely over. Among the exceptions are Giordano et. al. [1] and Bjornstad et. al. [2] who account for the possibility of re-infection – while the former find no special behaviour on account of this, the latter find an oscillatory approach towards the eventual equilibrium. In an article which appeared today, Kosinski [3] has found multiple waves of COVID-19 if the immunity threshold is finite. The question of whether COVID-19 re-infection can occur is completely open as of now. A study [4] has found that for benign coronaviruses (NOT the COVID-19 pathogen!), antibodies become significantly weaker six months after the original infection, and re-infection is common from one year onwards. Although it is currently unknown whether COVID-19 re-infections can occur, the mere possibility is sufficiently frightening as to warrant a discussion of what might happen if it is true. In this Article, we use mathematical modeling to present such a discussion. Before starting off, let us declare in the clearest possible terms that this entire Article is a what-if analysis, predicated on an assumption whose veracity is not known at the current time. The contents of this Article are therefore hypothetical – as of now they are neither factual nor counter-factual.

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Relative role of border restrictions, case finding and contact tracing in controlling SARS-CoV-2 in the presence of undetected transmission

10.1101/2021.05.05.21256675 ◽

2021 ◽

Author(s):

Rachael Pung ◽

Hannah E. Clapham ◽

Vernon J. Lee ◽

Adam J Kucharski ◽

Keyword(s):

Reproduction Number ◽

Relative Effectiveness ◽

Case Finding ◽

Contact Tracing ◽

Transmission Model ◽

Relative Role ◽

Outbreak Control ◽

Combining Data ◽

Different Types

Background Several countries have controlled the spread of COVID-19 through varying combinations of border restrictions, case finding, contact tracing and careful calibration on the resumption of domestic activities. However, evaluating the effectiveness of these measures based on observed cases alone is challenging as it does not reflect the transmission dynamics of missed infections. Methods Combining data on notified local COVID-19 cases with known and unknown sources of infections (i.e. linked and unlinked cases) in Singapore in 2020 with a transmission model, we reconstructed the incidence of missed infections and estimated the relative effectiveness of different types of outbreak control. We also examined implications for estimation of key real-time metrics -- the reproduction number and ratio of unlinked to linked cases, using observed data only as compared to accounting for missed infections. Findings Prior to the partial lockdown in Singapore, initiated in April 2020, we estimated 89% (95%CI 75-99%) of the infections caused by notified cases were contact traced, but only 12.5% (95%CI 2-69%) of the infections caused by missed infectors were identified. We estimated that the reproduction number was 1.23 (95%CI 0.98-1.54) after accounting for missed infections but was 0.90 (95%CI 0.79-1.1) based on notified cases alone. At the height of the outbreak, the ratio of missed to notified infections was 34.1 (95%CI 26.0-46.6) but the ratio of unlinked to linked infections was 0.81 (95%CI 0.59-1.36). Our results suggest that when case finding and contact tracing identifies at least 50% and 20% of the infections caused by missed and notified cases respectively, the reproduction number could be reduced by more than 14%, rising to 20% when contact tracing is 80% effective. Interpretation Depending on the relative effectiveness of border restrictions, case finding and contact tracing, unobserved outbreak dynamics can vary greatly. Commonly used metrics to evaluate outbreak control -- typically based on notified data -- could therefore misrepresent the true underlying outbreak. Funding Ministry of Health, Singapore.

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