scholarly journals Simulations of Infectious Disease Propagation II, Focusing on Herd Immunity

2021 ◽  
pp. 1-8
Author(s):  
William J. B. Oldham
Keyword(s):  
Infectious Disease ◽  
Population Density ◽  
Total Population ◽  
Herd Immunity ◽  
Infection Rates ◽  
Total Risk ◽  
Personal Involvement ◽  
Disease Propagation ◽  
The People ◽  
In The Beginning

Introduction and Objectives: The results of simulations of the propagation of an infectious disease are presented. In managing and controlling the spread of an infectious disease, such as Covid-19, the concept of Herd Immunity (HI) is often invoked as to when the disease’s propagation will dwindle to acceptable levels. We have extended a previous work with explicit attention on the usefulness of this concept. The objectives of this research was to track the propagation of an infectious disease as a function of population density, time, and to evaluate HI. The population was divided into two groups. One group was protected from the infection. The second group was unprotected. The results are given as a percentage of the unprotected population that is infected as a function of time. Methods: The method used here was to use computer simulation on a person level to follow the progress of the diseases infection across the population. In the beginning, the people are uniformly distributed in a square. Each person performed a random walk, which simulated the movement of the people. Infection rates are given for the unprotected portion of the population as a function of time. The disease was transferred from an infected person to an uninfected person if the two people are closer together than a given distance. Results and Discussion: These simulations show the unprotected portion of the population was at total risk if proper measures are not taken early. For 400 unprotected people the infection rate is 100% after approximately 100,000 iterations. We give the results from one dual simulation in which protection was afforded for a significant part of the population and carried out until all of the unprotected were infected. In the second part the protection was lifted to see how fast the total population was infected. For the case of 50% protected it took 400,000 iterations to infect the unprotected people. After the restrictions were lifted it took 150,000 to infect the other half. The simulations here were people based which has the advantage of seeing individual personal involvement. Results of infection rates were calculated for 1,000, 2,500, 5,000, and 10,000 people. Conclusions: The propagation of the disease can be fast and depends on population density. Protection is vital to containing the disease. Restrictions must be lifted carefully and slowly or the total population is again at risk. According to the results obtained here the concept of HI is not a viable concept in controlling or managing the spread of the disease.

scholarly journals Simulations of Infectious Disease Propagation

2020 ◽  
pp. 33-44
Author(s):  
William J. B. Oldham Jr.
Keyword(s):  
Infectious Disease ◽  
At Risk ◽  
Computer Simulation ◽  
Random Walk ◽  
Total Population ◽  
Particle Density ◽  
Critical Distance ◽  
The Other ◽  
Infection Rates ◽  
Disease Propagation

Introduction and Objectives: The results of two simulations of the propagation of an infectious disease are presented. The objective of this research is to track the propagation of an infectious disease as a function of particle density and time. The results are given as a percentage of the population that is infected as a function of time. Methods: The method here is to use computer simulation on a particle basis to track the progress of the infection. An uninfected particle becomes infected if it is closer than the critical distance to an infected particle. The movement of the particles is force driven in the first simulation while in the second each particle executes a random walk. In the second simulation the infection rates are given for different amounts of protection in the population. Results and Discussion: These simulations show the entire population is at risk if proper measures are not taken early. For 400 particles the infection rate is 100% after approximately 100,000 iterations.  We give the results from one dual simulation in which protection was afforded for a significant part of the population and carried out until all of the unprotected were infected.  In the second part the protection was lifted to see how fast the total population was infected. For the cases of 50% protected it took 400,000 iterations to infect the unprotected particles. After the restrictions were lifted it took 140,000 to infect the other half. The simulations here are particle based which has the advantage of seeing individual particle involvement. Conclusion: The propagation of the disease can be fast and depends on particle density. Protection is vital to containing the disease. Restrictions must be lifted carefully and slowly or the total population is again at risk.

Main Forms of Propagandistic Activities of the Right-Wing Parties (1904–1914)

2020 ◽  
Vol 102 ◽  
pp. 656-676
Author(s):  
Igor V. Omeliyanchuk
Keyword(s):  
20Th Century ◽  
Social Groups ◽  
Right Wing ◽  
Periodical Press ◽  
Political Movement ◽  
The People ◽  
The Social ◽  
The Right ◽  
In The Beginning ◽  
The 19Th Century

The article examines the main forms and methods of agitation and propagandistic activities of monarchic parties in Russia in the beginning of the 20th century. Among them the author singles out such ones as periodical press, publication of books, brochures and flyers, organization of manifestations, religious processions, public prayers and funeral services, sending deputations to the monarch, organization of public lectures and readings for the people, as well as various philanthropic events. Using various forms of propagandistic activities the monarchists aspired to embrace all social groups and classes of the population in order to organize all-class and all-estate political movement in support of the autocracy. While they gained certain success in promoting their ideology, the Rights, nevertheless, lost to their adversaries from the radical opposition camp, as the monarchists constrained by their conservative ideology, could not promise immediate social and political changes to the population, and that fact was excessively used by their opponents. Moreover, the ideological paradigm of the Right camp expressed in the “Orthodoxy, Autocracy, Nationality” formula no longer agreed with the social and economic realities of Russia due to modernization processes that were underway in the country from the middle of the 19th century.

scholarly journals SARS-CoV-2 infection is at herd immunity in the majority segment of the population of Qatar

2021 ◽  
Author(s):  
Mohamed H Al-Thani ◽  
Elmoubasher Farag ◽  
Roberto Bertollini ◽  
Hamad Eid Al Romaihi ◽  
Sami Abdeen ◽  
...  
Keyword(s):  
Total Population ◽  
Herd Immunity ◽  
Geographic Location ◽  
Population Based ◽  
Infection Prevalence ◽  
Cross Sectional ◽  
Previous Infection ◽  
Current Infection ◽  
Polymerase Chain ◽  
Population Based Survey

Abstract Background Qatar experienced a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic that disproportionately affected the craft and manual worker (CMW) population who comprise 60% of the total population. This study aimed to assess ever and/or current infection prevalence in this population. Methods A cross-sectional population-based survey was conducted during July 26-September 09, 2020 to assess both anti-SARS-CoV-2 positivity through serological testing and current infection positivity through polymerase chain reaction (PCR) testing. Associations with antibody and PCR positivity were identified through regression analyses. Results Study included 2,641 participants, 69.3% of whom were <40 years of age. Anti-SARS-CoV-2 positivity was 55.3% (95% CI: 53.3-57.3%) and was significantly associated with nationality, geographic location, educational attainment, occupation, and previous infection diagnosis. PCR positivity was 11.3% (95% CI: 9.9-12.8%) and was significantly associated with nationality, geographic location, occupation, contact with an infected person, and reporting two or more symptoms. Infection positivity (antibody and/or PCR positive) was 60.6% (95% CI: 58.6-62.5%). The proportion of antibody-positive CMWs that had a prior SARS-CoV-2 diagnosis was 9.3% (95% CI: 7.9-11.0%). Only seven infections were ever severe and one was ever critical—an infection severity rate of 0.5% (95% CI: 0.2-1.0%). Conclusions Six in every 10 CMWs have been infected, suggestive of reaching the herd immunity threshold. Infection severity was low with only one in every 200 infections progressing to be severe or critical. Only one in every 10 infections had been previously diagnosed suggestive of mostly asymptomatic or mild infections.

scholarly journals The Effect of Vaccination Rates on the Infection of COVID-19 under the Vaccination Rate below the Herd Immunity Threshold

2021 ◽  
Vol 18 (14) ◽  
pp. 7491
Author(s):  
Yi-Tui Chen
Keyword(s):  
Infection Rate ◽  
Herd Immunity ◽  
The United States ◽  
Vaccination Rate ◽  
Infection Rates ◽  
Vaccination Rates ◽  
The United Kingdom ◽  
The World ◽  
Almost All ◽  
The Impact

Although vaccination is carried out worldwide, the vaccination rate varies greatly. As of 24 May 2021, in some countries, the proportion of the population fully vaccinated against COVID-19 has exceeded 50%, but in many countries, this proportion is still very low, less than 1%. This article aims to explore the impact of vaccination on the spread of the COVID-19 pandemic. As the herd immunity of almost all countries in the world has not been reached, several countries were selected as sample cases by employing the following criteria: more than 60 vaccine doses per 100 people and a population of more than one million people. In the end, a total of eight countries/regions were selected, including Israel, the UAE, Chile, the United Kingdom, the United States, Hungary, and Qatar. The results find that vaccination has a major impact on reducing infection rates in all countries. However, the infection rate after vaccination showed two trends. One is an inverted U-shaped trend, and the other is an L-shaped trend. For those countries with an inverted U-shaped trend, the infection rate begins to decline when the vaccination rate reaches 1.46–50.91 doses per 100 people.

Effects of phytoseiid predators on the sex ratio of the spider mite Panonychus ulmi

1991 ◽  
Vol 69 (1) ◽  
pp. 208-212 ◽  
Author(s):  
Dan L. Johnson ◽  
Heather C. Proctor
Keyword(s):  
Population Density ◽  
Sex Ratio ◽  
Spider Mite ◽  
Total Population ◽  
Panonychus Ulmi ◽  
Encounter Rate ◽  
Male Mortality ◽  
Adult Sex Ratio ◽  
Biased Sex Ratio ◽  
Male Activity

The effect of predator presence on the adult sex ratio of a spider mite (Panonychus ulmi) was examined in a field experiment. Phytoseiid predators (chiefly Typhlodromus occidentalis) were removed from 32 trees harboring P. ulmi populations, and allowed to remain at natural levels on 32 other trees. Both total population density and proportion of males in the prey population were significantly higher in predator-free trees. Mechanisms that could explain the increase in the proportion of males are examined. The most probable is that greater male activity results in a higher encounter rate between predator and prey, and that subsequent higher male mortality when predators are present exaggerates the female-biased sex ratio. The theoretical effects of sex-biased predation on diplo-diploid and haplo-diploid organisms are discussed.

scholarly journals SPATIAL HETEROGENEITY IN SIMPLE DETERMINISTIC SIR MODELS ASSESSED ECOLOGICALLY

2012 ◽  
Vol 54 (1-2) ◽  
pp. 23-36 ◽  
Author(s):  
E. K. WATERS ◽  
H. S. SIDHU ◽  
G. N. MERCER
Keyword(s):  
Infectious Disease ◽  
Spatial Heterogeneity ◽  
Disease Transmission ◽  
Herd Immunity ◽  
Epidemic Models ◽  
Final Size ◽  
Infectious Disease Transmission ◽  
Epidemic Dynamics ◽  
Mean Crowding ◽  
Rate Of Movement

AbstractPatchy or divided populations can be important to infectious disease transmission. We first show that Lloyd’s mean crowding index, an index of patchiness from ecology, appears as a term in simple deterministic epidemic models of the SIR type. Using these models, we demonstrate that the rate of movement between patches is crucial for epidemic dynamics. In particular, there is a relationship between epidemic final size and epidemic duration in patchy habitats: controlling inter-patch movement will reduce epidemic duration, but also final size. This suggests that a strategy of quarantining infected areas during the initial phases of a virulent epidemic might reduce epidemic duration, but leave the population vulnerable to future epidemics by inhibiting the development of herd immunity.

scholarly journals The COVID-19 Pandemic Situation in Malaysia: Lessons Learned from the Perspective of Population Density

2021 ◽  
Vol 18 (12) ◽  
pp. 6566
Author(s):  
Siew Bee Aw ◽  
Bor Tsong Teh ◽  
Gabriel Hoh Teck Ling ◽  
Pau Chung Leng ◽  
Weng Howe Chan ◽  
...  
Keyword(s):  
Population Density ◽  
Pearson Correlation ◽  
Strong Relationship ◽  
Lessons Learned ◽  
P Value ◽  
Population Census ◽  
Infection Rates ◽  
Health Official ◽  
Contagious Diseases ◽  
Spatio Temporal

This paper attempts to ascertain the impacts of population density on the spread and severity of COVID-19 in Malaysia. Besides describing the spatio-temporal contagion risk of the virus, ultimately, it seeks to test the hypothesis that higher population density results in exacerbated COVID-19 virulence in the community. The population density of 143 districts in Malaysia, as per data from Malaysia’s 2010 population census, was plotted against cumulative COVID-19 cases and infection rates of COVID-19 cases, which were obtained from Malaysia’s Ministry of Health official website. The data of these three variables were collected between 19 January 2020 and 31 December 2020. Based on the observations, districts that have high population densities and are highly inter-connected with neighbouring districts, whether geographically, socio-economically, or infrastructurally, tend to experience spikes in COVID-19 cases within weeks of each other. Using a parametric approach of the Pearson correlation, population density was found to have a moderately strong relationship to cumulative COVID-19 cases (p-value of 0.000 and R2 of 0.415) and a weak relationship to COVID-19 infection rates (p-value of 0.005 and R2 of 0.047). Consequently, we provide several non-pharmaceutical lessons, including urban planning strategies, as passive containment measures that may better support disease interventions against future contagious diseases.

VARIABILITY FOR CARRIER-BORNE EPIDEMICS AND REED–FROST MODELS INCORPORATING UNCERTAINTIES AND DEPENDENCIES FROM SUSCEPTIBLES AND INFECTIVES

2010 ◽  
Vol 24 (2) ◽  
pp. 303-328 ◽  
Author(s):  
Eva María Ortega ◽  
Laureano F. Escudero
Keyword(s):  
Risk Assessment ◽  
Epidemic Model ◽  
Epidemic Models ◽  
Random Environments ◽  
Random Parameters ◽  
Infection Rates ◽  
Disease Propagation ◽  
Increasing Concave Order ◽  
Special Cases ◽  
Frost Model

This article provides analytical results on which are the implications of the statistical dependencies among certain random parameters on the variability of the number of susceptibles of the carrier-borne epidemic model with heterogeneous populations and of the number of infectives under the Reed–Frost model with random infection rates. We consider dependencies among the random infection rates, among the random infectious times, and among random initial susceptibles of several carrier-borne epidemic models. We obtain conditions for the variability ordering between the number of susceptibles for carrier-borne epidemics under two different random environments, at any time-scale value. These results are extended to multivariate comparisons of the random vectors of populations in the strata. We also obtain conditions for the increasing concave order between the number of infectives in the Reed–Frost model under two different random environments, for any generation. Variability bounds are obtained for different epidemic models from modeling dependencies for a range of special cases that are useful for risk assessment of disease propagation.

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