scholarly journals Temporary Immunity and Multiple Waves of COVID-19

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.

scholarly journals Assessment of Morphology Changes of the End Moraine of the Werenskiold Glacier (SW Spitsbergen) Using Active and Passive Remote Sensing Techniques

2021 ◽  
Vol 13 (11) ◽  
pp. 2134
Author(s):  
Tadeusz Głowacki ◽  
Damian Kasza
Keyword(s):  
Morphological Changes ◽  
Time Interval ◽  
Dynamic Surface ◽  
Near Surface ◽  
Passive Remote Sensing ◽  
Synthetic Aperture Radar Interferometry ◽  
Aerial Photogrammetry ◽  
Remote Sensing Techniques ◽  
One Year

Wedel Jarlsberg Land in Svalbard is a region with a varied periglacial landscape. In the mountains and in the valleys, the climate is polar with permafrost. During the summer, the near-surface ground layer thaws. The Werenskiold Glacier, together with its end moraine, are located in the central part of this area. The rate of morphological changes observed within the moraine varies in time and space, and depends on the environmental conditions. This study investigates four periods of archival aerial photogrammetry measurements (1936, 1960, 1990, and 2011) performed for the end moraine of the glacier. The long-term analysis was also based on a direct GNSS RTK survey from 2015. Over a period of almost 80 years, more than 14 million m3 of rock and ice material disappeared from the end moraine of the glacier (an average of approximately 200 thousand m3/year). Analyses of the dynamic surface changes over one year (2015) were performed with the use of synthetic aperture radar interferometry (InSAR). The time interval between images was in this case 12 days and covered (simultaneously in each scene) the entire investigated area. In this case, the analysis demonstrated that over a period of only 4 months, the moraine lost 200 thousand m3 of material (approximately two thousand m3/day), which is equivalent to the entire annual mass loss of the moraine.

Application of the method of mathematical modeling for forecasting channel deformations at the underwater crossing of the main pipeline

2020 ◽  
Vol 10 (6) ◽  
pp. 599-609
Author(s):  
Valery А. Gruzdev ◽  
◽  
Georgy V. Mosolov ◽  
Ekaterina A. Sabayda ◽  
◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Mathematical Model ◽  
Roughness Coefficient ◽  
Computational Domain ◽  
Channel Deformations ◽  
Geological Surveys ◽  
Kuban River ◽  
The Stability ◽  
Protective Structures

In order to determine the possibility of using the method of mathematical modeling for making long-term forecasts of channel deformations of trunk line underwater crossing (TLUC) through water obstacles, a methodology for performing and analyzing the results of mathematical modeling of channel deformations in the TLUC zone across the Kuban River is considered. Within the framework of the work, the following tasks were solved: 1) the format and composition of the initial data necessary for mathematical modeling were determined; 2) the procedure for assigning the boundaries of the computational domain of the model was considered, the computational domain was broken down into the computational grid, the zoning of the computational domain was performed by the value of the roughness coefficient; 3) the analysis of the results of modeling the water flow was carried out without taking the bottom deformations into account, as well as modeling the bottom deformations, the specifics of the verification and calibration calculations were determined to build a reliable mathematical model; 4) considered the possibility of using the method of mathematical modeling to check the stability of the bottom in the area of TLUC in the presence of man-made dumping or protective structure. It has been established that modeling the flow hydraulics and structure of currents, making short-term forecasts of local high-altitude reshaping of the bottom, determining the tendencies of erosion and accumulation of sediments upstream and downstream of protective structures are applicable for predicting channel deformations in the zone of the TLUC. In all these cases, it is mandatory to have materials from engineering-hydro-meteorological and engineering-geological surveys in an amount sufficient to compile a reliable mathematical model.

scholarly journals A206 EVOLUTION OF PEDIATRIC AUTOIMMUNE CHOLANGITIS AND PRIMARY SCLEROSING CHOLANGITIS INTO ADULTHOOD

2021 ◽  
Vol 4 (Supplement_1) ◽  
pp. 234-236
Author(s):  
P Willems ◽  
J Hercun ◽  
C Vincent ◽  
F Alvarez
Keyword(s):  
Primary Sclerosing Cholangitis ◽  
Sclerosing Cholangitis ◽  
Response To Treatment ◽  
Similar Proportion ◽  
Autoimmune Cholangitis ◽  
Significant Difference ◽  
One Year ◽  
Liver Tests

Abstract Background The natural history of primary sclerosing cholangitis (PSC) in children seems to differ from PSC in adults. However, studies on this matter have been limited by short follow-up periods and inconsistent classification of patients with autoimmune cholangitis (AIC) (or overlap syndrome). Consequently, it remains unclear if long-term outcomes are affected by the clinical phenotype. Aims The aims of this is study are to describe the long-term evolution of PSC and AIC in a pediatric cohort with extension of follow-up into adulthood and to evaluate the influence of phenotype on clinical outcomes. Methods This is a retrospective study of patients with AIC or PSC followed at CHU-Sainte-Justine, a pediatric referral center in Montreal. All charts between January 1998 and December 2019 were reviewed. Patients were classified as either AIC (duct disease on cholangiography with histological features of autoimmune hepatitis) or PSC (large or small duct disease on cholangiography and/or histology). Extension of follow-up after the age of 18 was done for patients followed at the Centre hospitalier de l’Université de Montréal. Clinical features at diagnosis, response to treatment at one year and liver-related outcomes were compared. Results 40 patients (27 PSC and 13 AIC) were followed for a median time of 71 months (range 2 to 347), with 52.5% followed into adulthood. 70% (28/40) had associated inflammatory bowel disease (IBD) (78% PSC vs 54% AIC; p=0.15). A similar proportion of patients had biopsy-proven significant fibrosis at diagnosis (45% PSC vs 67% AIC; p=0.23). Baseline liver tests were similar in both groups. At diagnosis, all patients were treated with ursodeoxycholic acid. Significantly more patients with AIC (77% AIC vs 30 % PSC; p=0.005) were initially treated with immunosuppressive drugs, without a significant difference in the use of Anti-TNF agents (0% AIC vs 15% PSC; p= 0.12). At one year, 55% (15/27) of patients in the PSC group had normal liver tests versus only 15% (2/13) in the AIC group (p=0.02). During follow-up, more liver-related events (cholangitis, liver transplant and cirrhosis) were reported in the AIC group (HR=3.7 (95% CI: 1.4–10), p=0.01). Abnormal liver tests at one year were a strong predictor of liver-related events during follow-up (HR=8.9(95% CI: 1.2–67.4), p=0.03), while having IBD was not (HR=0.48 (95% CI: 0.15–1.5), p=0.22). 5 patients required liver transplantation with no difference between both groups (8% CAI vs 15% CSP; p=0.53). Conclusions Pediatric patients with AIC and PSC show, at onset, similar stage of liver disease with comparable clinical and biochemical characteristics. However, patients with AIC receive more often immunosuppressive therapy and treatment response is less frequent. AIC is associated with more liver-related events and abnormal liver tests at one year are predictor of bad outcomes. Funding Agencies None

scholarly journals Role of efficient testing and contact tracing in mitigating the COVID-19 pandemic: a network modelling study

BMJ Open ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. e045886
Author(s):  
Yiying Hu ◽  
Jianying Guo ◽  
Guanqiao Li ◽  
Xi Lu ◽  
Xiang Li ◽  
...  
Keyword(s):  
Real World ◽  
Case Fatality ◽  
Contact Tracing ◽  
Secondary Outcome ◽  
Time Interval ◽  
Fatality Rate ◽  
Real World Data ◽  
Network Modelling ◽  
World Data ◽  
Quantitative Evidence

ObjectivesThis study quantified how the efficiency of testing and contact tracing impacts the spread of COVID-19. The average time interval between infection and quarantine, whether asymptomatic cases are tested or not, and initial delays to beginning a testing and tracing programme were investigated.SettingWe developed a novel individual-level network model, called CoTECT (Testing Efficiency and Contact Tracing model for COVID-19), using key parameters from recent studies to quantify the impacts of testing and tracing efficiency. The model distinguishes infection from confirmation by integrating a ‘T’ compartment, which represents infections confirmed by testing and quarantine. The compartments of presymptomatic (E), asymptomatic (I), symptomatic (Is), and death with (F) or without (f) test confirmation were also included in the model. Three scenarios were evaluated in a closed population of 3000 individuals to mimic community-level dynamics. Real-world data from four Nordic countries were also analysed.Primary and secondary outcome measuresSimulation result: total/peak daily infections and confirmed cases, total deaths (confirmed/unconfirmed by testing), fatalities and the case fatality rate. Real-world analysis: confirmed cases and deaths per million people.Results(1) Shortening the duration between Is and T from 12 to 4 days reduces infections by 85.2% and deaths by 88.8%. (2) Testing and tracing regardless of symptoms reduce infections by 35.7% and deaths by 46.2% compared with testing only symptomatic cases. (3) Reducing the delay to implementing a testing and tracing programme from 50 to 10 days reduces infections by 35.2% and deaths by 44.6%. These results were robust to sensitivity analysis. An analysis of real-world data showed that tests per case early in the pandemic are critical for reducing confirmed cases and the fatality rate.ConclusionsReducing testing delays will help to contain outbreaks. These results provide policymakers with quantitative evidence of efficiency as a critical value in developing testing and contact tracing strategies.

scholarly journals “The Looming, Crazy Stalker Coronavirus”: Fear Mongering, Fake News, and the Diffusion of Distrust

2021 ◽  
Vol 7 ◽  
pp. 237802312110247
Author(s):  
Alexandrea J. Ravenelle ◽  
Abigail Newell ◽  
Ken Cai Kowalski
Keyword(s):  
Mental Health ◽  
Media Coverage ◽  
Media Consumption ◽  
Fake News ◽  
Compensatory Control ◽  
The Media ◽  
Good For ◽  
Fear Mongering ◽  
One Year

The authors explore media distrust among a sample of precarious and gig workers interviewed during the COVID-19 pandemic. Although these left-leaning respondents initially increased their media consumption at the outset of the pandemic, they soon complained of media sensationalism and repurposed a readily available cultural tool: claims of “fake news.” As a result, these unsettled times have resulted in a “diffusion of distrust,” in which an elite conservative discourse of skepticism toward the media has also become a popular form of compensatory control among self-identified liberals. Perceiving “fake news” and media sensationalism as “not good” for their mental health, respondents also reported experiencing media burnout and withdrawing from media consumption. As the pandemic passes its one-year anniversary, this research has implications for long-term media coverage on COVID-19 and ongoing media trust and consumption.

scholarly journals Short- and long-term effects of ponderosa pine fuel treatments intersected by the Egley Fire Complex, Oregon, USA

Fire Ecology ◽  
2019 ◽  
Vol 15 (1) ◽  
Author(s):  
Jessie M. Dodge ◽  
Eva K. Strand ◽  
Andrew T. Hudak ◽  
Benjamin C. Bright ◽  
Darcy H. Hammond ◽  
...  
Keyword(s):  
Prescribed Fire ◽  
Vegetation Cover ◽  
Tree Density ◽  
Tree Canopy ◽  
Fuel Treatments ◽  
Dead Tree ◽  
High Severity ◽  
Short And Long Term ◽  
One Year

Abstract Background Fuel treatments are widely used to alter fuels in forested ecosystems to mitigate wildfire behavior and effects. However, few studies have examined long-term ecological effects of interacting fuel treatments (commercial harvests, pre-commercial thinnings, pile and burning, and prescribed fire) and wildfire. Using annually fitted Landsat satellite-derived Normalized Burn Ratio (NBR) curves and paired pre-fire treated and untreated field sites, we tested changes in the differenced NBR (dNBR) and years since treatment as predictors of biophysical attributes one and nine years after the 2007 Egley Fire Complex in Oregon, USA. We also assessed short- and long-term fuel treatment impacts on field-measured attributes one and nine years post fire. Results One-year post-fire burn severity (dNBR) was lower in treated than in untreated sites across the Egley Fire Complex. Annual NBR trends showed that treated sites nearly recovered to pre-fire values four years post fire, while untreated sites had a slower recovery rate. Time since treatment and dNBR significantly predicted tree canopy and understory green vegetation cover in 2008, suggesting that tree canopy and understory vegetation cover increased in areas that were treated recently pre fire. Live tree density was more affected by severity than by pre-fire treatment in either year, as was dead tree density one year post fire. In 2008, neither treatment nor severity affected percent cover of functional groups (shrub, graminoid, forb, invasive, and moss–lichen–fungi); however, by 2016, shrub, graminoid, forb, and invasive cover were higher in high-severity burn sites than in low-severity burn sites. Total fuel loads nine years post fire were higher in untreated, high-severity burn sites than any other sites. Tree canopy cover and density of trees, saplings, and seedlings were lower nine years post fire than one year post fire across treatments and severity, whereas live and dead tree basal area, understory surface cover, and fuel loads increased. Conclusions Pre-fire fuel treatments effectively lowered the occurrence of high-severity wildfire, likely due to successful pre-fire tree and sapling density and surface fuels reduction. This study also quantified the changes in vegetation and fuels from one to nine years post fire. We suggest that low-severity wildfire can meet prescribed fire management objectives of lowering surface fuel accumulations while not increasing overstory tree mortality.

scholarly journals Is It Definitely Clear That Long-Term Survival after Breast Cancer Surgery Is Not Affected by Anaesthetics?

Cancers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 3390
Author(s):  
Mats Enlund
Keyword(s):  
Breast Cancer ◽  
Survival Data ◽  
Retrospective Studies ◽  
Breast Cancer Surgery ◽  
Breast Cancer Patients ◽  
Term Survival ◽  
Long Term Survival ◽  
Significant Difference ◽  
One Year

Retrospective studies indicate that cancer survival may be affected by the anaesthetic technique. Propofol seems to be a better choice than volatile anaesthetics, such as sevoflurane. The first two retrospective studies suggested better long-term survival with propofol, but not for breast cancer. Subsequent retrospective studies from Asia indicated the same. When data from seven Swedish hospitals were analysed, including 6305 breast cancer patients, different analyses gave different results, from a non-significant difference in survival to a remarkably large difference in favour of propofol, an illustration of the innate weakness in the retrospective design. The largest randomised clinical trial, registered on clinicaltrial.gov, with survival as an outcome is the Cancer and Anesthesia study. Patients are here randomised to propofol or sevoflurane. The inclusion of patients with breast cancer was completed in autumn 2017. Delayed by the pandemic, one-year survival data for the cohort were presented in November 2020. Due to the extremely good short-term survival for breast cancer, one-year survival is of less interest for this disease. As the inclusions took almost five years, there was also a trend to observe. Unsurprisingly, no difference was found in one-year survival between the two groups, and the trend indicated no difference either.

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