scholarly journals How optimal allocation of limited testing capacity changes epidemic dynamics

2020 ◽  
Author(s):  
Justin M. Calabrese ◽  
Jeffery Demers
Keyword(s):  
Optimal Allocation ◽  
Clinical Testing ◽  
Epidemic Dynamics ◽  
Response Planning ◽  
Early Implementation ◽  
Information Parameter ◽  
High Infection ◽  
Optimal Mix ◽  
Asymptomatic Individuals ◽  
Limited Testing

AbstractInsufficient testing capacity continues to be a critical bottleneck in the worldwide fight against COVID-19. Optimizing the deployment of limited testing resources has therefore emerged as a keystone problem in pandemic response planning. Here, we use a modified SEIR model to optimize testing strategies under a constraint of limited testing capacity. We define pre-symptomatic, asymptomatic, and symptomatic infected classes, and assume that positively tested individuals are immediately moved into quarantine. We further define two types of testing. Clinical testing focuses only on the symptomatic class. Non-clinical testing detects pre- and asymptomatic individuals from the general population, and an “information” parameter governs the degree to which such testing can be focused on high infection risk individuals. We then solve for the optimal mix of clinical and non-clinical testing as a function of both testing capacity and the information parameter. We find that purely clinical testing is optimal at very low testing capacities, supporting early guidance to ration tests for the sickest patients. Additionally, we find that a mix of clinical and non-clinical testing becomes optimal as testing capacity increases. At high but empirically observed testing capacities, a mix of clinical testing and unfocused (information=0) non-clinical testing becomes optimal. We further highlight the advantages of early implementation of testing programs, and of combining optimized testing with contact reduction interventions such as lockdowns, social distancing, and masking.

scholarly journals Reconstructing the early global dynamics of under-ascertained COVID-19 cases and infections

BMC Medicine ◽  
2020 ◽  
Vol 18 (1) ◽  
Author(s):  
Timothy W. Russell ◽  
◽  
Nick Golding ◽  
Joel Hellewell ◽  
Sam Abbott ◽  
...  
Keyword(s):  
Process Model ◽  
Case Fatality ◽  
Sudden Onset ◽  
Control Measures ◽  
Global Dynamics ◽  
Median Percentage ◽  
Epidemic Dynamics ◽  
Response Planning ◽  
Seroprevalence Data ◽  
Reported Data

Abstract Background Asymptomatic or subclinical SARS-CoV-2 infections are often unreported, which means that confirmed case counts may not accurately reflect underlying epidemic dynamics. Understanding the level of ascertainment (the ratio of confirmed symptomatic cases to the true number of symptomatic individuals) and undetected epidemic progression is crucial to informing COVID-19 response planning, including the introduction and relaxation of control measures. Estimating case ascertainment over time allows for accurate estimates of specific outcomes such as seroprevalence, which is essential for planning control measures. Methods Using reported data on COVID-19 cases and fatalities globally, we estimated the proportion of symptomatic cases (i.e. any person with any of fever ≥ 37.5 °C, cough, shortness of breath, sudden onset of anosmia, ageusia or dysgeusia illness) that were reported in 210 countries and territories, given those countries had experienced more than ten deaths. We used published estimates of the baseline case fatality ratio (CFR), which was adjusted for delays and under-ascertainment, then calculated the ratio of this baseline CFR to an estimated local delay-adjusted CFR to estimate the level of under-ascertainment in a particular location. We then fit a Bayesian Gaussian process model to estimate the temporal pattern of under-ascertainment. Results Based on reported cases and deaths, we estimated that, during March 2020, the median percentage of symptomatic cases detected across the 84 countries which experienced more than ten deaths ranged from 2.4% (Bangladesh) to 100% (Chile). Across the ten countries with the highest number of total confirmed cases as of 6 July 2020, we estimated that the peak number of symptomatic cases ranged from 1.4 times (Chile) to 18 times (France) larger than reported. Comparing our model with national and regional seroprevalence data where available, we find that our estimates are consistent with observed values. Finally, we estimated seroprevalence for each country. As of 7 June, our seroprevalence estimates range from 0% (many countries) to 13% (95% CrI 5.6–24%) (Belgium). Conclusions We found substantial under-ascertainment of symptomatic cases, particularly at the peak of the first wave of the SARS-CoV-2 pandemic, in many countries. Reported case counts will therefore likely underestimate the rate of outbreak growth initially and underestimate the decline in the later stages of an epidemic. Although there was considerable under-reporting in many locations, our estimates were consistent with emerging serological data, suggesting that the proportion of each country’s population infected with SARS-CoV-2 worldwide is generally low.

scholarly journals Emergency Physician Performed Ultrasound for DVT Evaluation

Thrombosis ◽  
2011 ◽  
Vol 2011 ◽  
pp. 1-4 ◽  
Author(s):  
John Christian Fox ◽  
Kiah Christine Bertoglio
Keyword(s):  
Deep Vein Thrombosis ◽  
Improve Patient Care ◽  
Cost Effective ◽  
Diagnostic Tools ◽  
Delayed Imaging ◽  
Vein Thrombosis ◽  
Early Implementation ◽  
Cost Effective Treatment ◽  
Asymptomatic Individuals ◽  
Deep Vein

Deep vein thrombosis is a common condition that is often difficult to diagnose and may be lethal when allowed to progress. However, early implementation of treatment substantially improves the disease prognosis. Therefore, care must be taken to both acquire an accurate differential diagnosis for patients with symptoms as well as to screen at-risk asymptomatic individuals. Many diagnostic tools exist to evaluate deep vein thrombosis. Compression ultrasonography is currently the most effective diagnostic tool in the emergency department, shown to be highly accurate at minimal expense. However, limited availability of ultrasound technicians may result in delayed imaging or in a decision not to image low-risk cases. Many studies support emergency physiciansas capable of accurately diagnosing deep vein thrombosis using bedside ultrasound. Further integration of ultrasound into the training of emergency physicians for use in evaluating deep vein thrombosis will improve patient care and cost-effective treatment.

scholarly journals Discontinuous epidemic transition due to limited testing

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Davide Scarselli ◽  
Nazmi Burak Budanur ◽  
Marc Timme ◽  
Björn Hof
Keyword(s):  
Exponential Growth ◽  
Growth Period ◽  
High Impact ◽  
Contact Tracing ◽  
Epidemic Dynamics ◽  
Slowing Down ◽  
Containment Measures ◽  
Second Wave ◽  
Limited Testing ◽  
Pharmaceutical Interventions

AbstractHigh impact epidemics constitute one of the largest threats humanity is facing in the 21st century. In the absence of pharmaceutical interventions, physical distancing together with testing, contact tracing and quarantining are crucial in slowing down epidemic dynamics. Yet, here we show that if testing capacities are limited, containment may fail dramatically because such combined countermeasures drastically change the rules of the epidemic transition: Instead of continuous, the response to countermeasures becomes discontinuous. Rather than following the conventional exponential growth, the outbreak that is initially strongly suppressed eventually accelerates and scales faster than exponential during an explosive growth period. As a consequence, containment measures either suffice to stop the outbreak at low total case numbers or fail catastrophically if marginally too weak, thus implying large uncertainties in reliably estimating overall epidemic dynamics, both during initial phases and during second wave scenarios.

scholarly journals A note on the effects of epidemic forecasts on epidemic dynamics

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9649 ◽  
Author(s):  
Nicholas R. Record ◽  
Andrew Pershing
Keyword(s):  
Human Behavior ◽  
Coupled System ◽  
Human System ◽  
Epidemic Dynamics ◽  
Response Planning ◽  
System A ◽  
Infection Dynamics ◽  
Functional Forms ◽  
Current Infection ◽  
Lower Infection

The purpose of a forecast, in making an estimate about the future, is to give people information to act on. In the case of a coupled human system, a change in human behavior caused by the forecast can alter the course of events that were the subject of the forecast. In this context, the forecast is an integral part of the coupled human system, with two-way feedback between forecast output and human behavior. However, forecasting programs generally do not examine how the forecast might affect the system in question. This study examines how such a coupled system works using a model of viral infection—the susceptible-infected-removed (SIR) model—when the model is used in a forecasting context. Human behavior is modified by making the contact rate responsive to other dynamics, including forecasts, of the SIR system. This modification creates two-way feedback between the forecast and the infection dynamics. Results show that a faster rate of response by a population to system dynamics or forecasts leads to a significant decline in peak infections. Responding to a forecast leads to a lower infection peak than responding to current infection levels. Inaccurate forecasts can lead to either higher or lower peak infections depending on whether the forecast under-or over-estimates the peak. The direction of inaccuracy in a forecast determines whether the outcome is better or worse for the population. While work is still needed to constrain model functional forms, forecast feedback can be an important component of epidemic dynamics that should be considered in response planning.

scholarly journals Optimal allocation of PCR tests to minimise disease transmission through contact tracing and quarantine

2021 ◽  
Author(s):  
Christopher M Baker ◽  
Iadine Chades ◽  
Jodie McVernon ◽  
Andrew Robinson ◽  
Howard Bondell
Keyword(s):  
Disease Transmission ◽  
Performance Metrics ◽  
Optimal Allocation ◽  
Information Gain ◽  
Disease Outbreaks ◽  
Limited Resource ◽  
Contact Tracing ◽  
Testing System ◽  
Epidemic Dynamics ◽  
Modelling Framework

PCR testing is a crucial capability for managing disease outbreaks, but it is also a limited resource and must be used carefully to ensure the information gain from testing is valuable. Testing has two broad uses, namely to track epidemic dynamics and to reduce transmission by identifying and managing cases. In this work we develop a modelling framework to examine the effects of test allocation in an epidemic, with a focus on using testing to minimise transmission. Using the COVID-19 pandemic as an example, we examine how the number of tests conducted per day relates to reduction in disease transmission, in the context of logistical constraints on the testing system. We show that if daily testing is above the routine capacity of a testing system, which can cause delays, then those delays can undermine efforts to reduce transmission through contact tracing and quarantine. This work highlights that the two goals of aiming to reduce transmission and aiming to identify all cases are different, and it is possible that focusing on one may undermine achieving the other. To develop an effective strategy, the goals must be clear and performance metrics must match the goals of the testing strategy. If metrics do not match the objectives of the strategy, then those metrics may incentivise actions that undermine achieving the objectives.

scholarly journals Optimal Allocation of Limited Test Resources for the Quantification of COVID-19 Infections

2020 ◽  
Author(s):  
Michail Chatzimanolakis ◽  
Pascal Weber ◽  
George Arampatzis ◽  
Daniel Wälchli ◽  
Ivica Kičić ◽  
...  
Keyword(s):  
Decision Making ◽  
Experimental Design ◽  
Open Source Software ◽  
Policy Making ◽  
Optimal Allocation ◽  
Reproduction Number ◽  
Information Gain ◽  
The World ◽  
Systematic Identification ◽  
Limited Testing

AbstractThe systematic identification of infected individuals is critical for the containment of the COVID-19 pandemic. Presently, the spread of the disease is mostly quantified by the reported numbers of infections, hospitalizations, recoveries and deaths; these quantities inform epidemiology models that provide forecasts for the spread of the epidemic and guide policy making. The veracity of these forecasts depends on the discrepancy between the numbers of reported and unreported, yet infectious, individuals.We combine Bayesian experimental design with an epidemiology model and propose a methodology for the optimal allocation of limited testing resources in space and time, which maximizes the information gain for such unreported infections. The proposed approach is applicable at the onset and spreading of the epidemic and can forewarn for a possible recurrence of the disease after relaxation of interventions. We examine its application in Switzerland; the open source software is, however, readily adaptable to countries around the world.We find that following the proposed methodology can lead to vastly less uncertain predictions for the spread of the disease. Estimates of the effective reproduction number and of the future number of unreported infections are improved, which in turn can provide timely and systematic guidance for the effective identification of infectious individuals and for decision-making.

Pandemic will hit Costa Rica’s welfare systems

2020 ◽  
Keyword(s):  
Latin America ◽  
Warning Sign ◽  
Infection Rates ◽  
Public System ◽  
Content Type ◽  
The Public ◽  
Health Funding ◽  
Early Implementation ◽  
High Infection ◽  
Welfare Systems

Significance A strong healthcare system together with early implementation of social distancing measures and social assistance support has kept contagion levels low. The crisis is nevertheless hitting health funding particularly hard as a result of growing unemployment and insufficient payroll contributions. Impacts Lack of regulation of private health provision could increase health inequalities and further erode the public system. High infection rates in Panama and likely under-reporting in Nicaragua will see Costa Rica maintain border restrictions for the time being. The country’s decision to slow down its economic re-opening is a warning sign for the rest of Latin America.

scholarly journals Improved Epidemic Dynamics Model and Its Prediction for COVID-19 in Italy

2020 ◽  
Vol 10 (14) ◽  
pp. 4930 ◽  
Author(s):  
Han Wang ◽  
Kang Xu ◽  
Zhongyi Li ◽  
Kexin Pang ◽  
Hua He
Keyword(s):  
Global Public Health ◽  
Dynamics Model ◽  
Transmission Characteristics ◽  
Health Crisis ◽  
Epidemic Dynamics ◽  
Public Health Crisis ◽  
Model Combining ◽  
Long Time ◽  
The Government ◽  
Asymptomatic Individuals

The outbreak of coronavirus disease 2019 (COVID-19) has become a global public health crisis due to its high contagious characteristics. In this article, we propose a new epidemic-dynamics model combining the transmission characteristics of COVID-19 and then use the reported epidemic data from 15 February to 30 June to simulate the spread of the Italian epidemic. Numerical simulations showed that (1) there was a remarkable amount of asymptomatic individuals; (2) the lockdown measures implemented by Italy effectively controlled the spread of the outbreak; (3) the Italian epidemic has been effectively controlled, but SARS-CoV-2 will still exist for a long time; and (4) the intervention of the government is an important factor that affects the spread of the epidemic.

scholarly journals Reconstructing the early global dynamics of under-ascertained COVID-19 cases and infections

2020 ◽  
Author(s):  
Timothy W Russell ◽  
Nick Golding ◽  
Joel Hellewell ◽  
Sam Abbott ◽  
Lawrence Wright ◽  
...  
Keyword(s):  
Process Model ◽  
Case Fatality ◽  
Sudden Onset ◽  
Control Measures ◽  
Global Dynamics ◽  
Median Percentage ◽  
Epidemic Dynamics ◽  
Response Planning ◽  
Seroprevalence Data ◽  
Reported Data

Background: Asymptomatic or subclinical SARS-CoV-2 infections are often unreported, which means that confirmed case counts may not accurately reflect underlying epidemic dynamics. Understanding the level of ascertainment (the ratio of confirmed symptomatic cases to the true number of symptomatic individuals) and undetected epidemic progression is crucial to informing COVID-19 response planning, including the introduction and relaxation of control measures. Estimating case ascertainment over time allows for accurate estimates of specific outcomes such as seroprevalence, which is essential for planning control measures. Methods: Using reported data on COVID-19 cases and fatalities globally, we estimated the proportion of symptomatic cases (i.e. any person with any of fever >= 37.5C, cough, shortness of breath, sudden onset of anosmia, ageusia or dysgeusia illness) that were reported in 210 countries and territories, given those countries had experienced more than ten deaths. We used published estimates of the baseline case fatality ratio (CFR), which was adjusted for delays and under-ascertainment, then calculated the ratio of this baseline CFR to an estimated local delay-adjusted CFR to estimate the level of under-ascertainment in a particular location. We then fit a Bayesian Gaussian process model to estimate the temporal pattern of under-ascertainment. Results: Based on reported cases and deaths, we estimated that, during March 2020, the median percentage of symptomatic cases detected across the 84 countries which experienced more than ten deaths ranged from 2.4% (Bangladesh) to 100% (Chile). Across the ten countries with the highest number of total confirmed cases as of 6th July 2020, we estimated that the peak number of symptomatic cases ranged from 1.4 times (Chile) to 18 times (France) larger than reported. Comparing our model with national and regional seroprevalence data where available, we find that our estimates are consistent with observed values. Finally, we estimated seroprevalence for each country. As of the 7th June, our seroprevalence estimates range from 0% (many countries) to 13% (95% CrI: 5.6% - 24%) (Belgium). Conclusions: We found substantial under-ascertainment of symptomatic cases, particularly at the peak of the first wave of the SARS-CoV-2 pandemic, in many countries. Reported case counts will therefore likely underestimate the rate of outbreak growth initially and underestimate the decline in the later stages of an epidemic. Although there was considerable under-reporting in many locations, our estimates were consistent with emerging serological data, suggesting that the proportion of each country's population infected with SARS-CoV-2 worldwide is generally low.

Spine Impairment Evaluation: Sixth Edition Approaches

2009 ◽  
Vol 14 (1) ◽  
pp. 1-5
Author(s):  
Craig Uejo ◽  
Marjorie Eskay-Auerbach ◽  
Christopher R. Brigham
Keyword(s):  
Functional Status ◽  
Spinal Injury ◽  
Current Medical ◽  
Clinical Testing ◽  
Medical Evidence ◽  
Sixth Edition ◽  
Whole Person ◽  
Rating Process ◽  
Impairment Ratings ◽  
Class Assignment

Abstract Evaluators who use the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Sixth Edition, should understand the significant changes that have occurred (as well as the Clarifications and Corrections) in impairment ratings for disorders of the cervical spine, thoracic spine, lumbar spine, and pelvis. The new methodology is an expansion of the Diagnosis-related estimates (DRE) method used in the fifth edition, but the criteria for defining impairment are revised, and the impairment value within a class is refined by information related to functional status, physical examination findings, and the results of clinical testing. Because current medical evidence does not support range-of-motion (ROM) measurements of the spine as a reliable indicator of specific pathology or permanent functional status, ROM is no longer used as a basis for defining impairment. The DRE method should standardize and simplify the rating process, improve validity, and provide a more uniform methodology. Table 1 shows examples of spinal injury impairment rating (according to region of the spine and category, with comments about the diagnosis and the resulting class assignment); Table 2 shows examples of spine impairment by region of the spine, class, diagnosis, and associated whole person impairment ratings form the sixth and fifth editions of the AMA Guides.

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