Modeling for COVID-19 with the contacting distance.

COVID-19 is a public health emergency for human beings and brings some very harmful consequences in social and economic fields. In order to model COVID-19 and develop the effective control measures, this paper proposes an SEIR-type epidemic model with the contacting distance between the healthy individuals and the asymptomatic or symptomatic infected individuals, and the immigration rate of the healthy individuals since the contacting distance and the immigration rate are two critical factors which determine the transmission of COVID-19. Firstly, the threshold values of the contacting distance and the immigration rate are obtained to analyze the presented model. Secondly, based on the data from January 10, 2020, to March 18, 2020, for Wuhan city, all parameters are estimated. Finally, based on the estimated parameters, the sensitivity analysis and the numerical study are conducted. The results show that the contacting distance and the immigration rate play an important role in controlling COVID-19. Meanwhile, the extinct lag decreases as the contacting distance increases and/or the immigration rate decreases. Our study could give some reasonable suggestions for the health officials and the public and provide a theoretical issue for globally controlling the COVID-19 pandemic.

Study of transmission dynamics of novel COVID-19 by using mathematical model.

In this research work, we present a mathematical model for novel coronavirus-19 infectious disease which consists of three different compartments: susceptible, infected, and recovered under convex incident rate involving immigration rate. We first derive the formulation of the model. Also, we give some qualitative aspects for the model including existence of equilibriums and its stability results by using various tools of nonlinear analysis. Then, by means of the nonstandard finite difference scheme (NSFD), we simulate the results for the data of Wuhan city against two different sets of values of immigration parameter. By means of simulation, we show how protection, exposure, death, and cure rates affect the susceptible, infected, and recovered population with the passage of time involving immigration. On the basis of simulation, we observe the dynamical behavior due to immigration of susceptible and infected classes or one of these two.

Quantifying the contribution of immigration to population dynamics: a review of methods, evidence and perspectives in birds and mammals.

The demography of a population is often reduced to the apparent (or local) survival of individuals and their realised fecundity within a study area defined according to logistical constraints rather than landscape features. Such demographics are then used to infer whether a local population contributes positively to population dynamics across a wider landscape context. Such a simplistic approach ignores a fundamental process underpinning population dynamics: dispersal. Indeed, it has long been accepted that immigration contributed by dispersers that emigrated from neighbouring populations may strongly influence the net growth of a local population. To date however, we lack a clear picture of how widely immigration rate varies both among and within populations, in relation to extrinsic and intrinsic ecological conditions, even for the best-studied avian and mammalian populations. This empirical knowledge gap precludes the emergence of a sound conceptual framework that ought to inform conservation and population ecology. This review, conducted on both birds and mammals, has thus three complementary objectives. First, we describe and evaluate the relative merits of methods used to quantify immigration and how they relate to widely applicable metrics. We identify two simple and unifying metrics to measure immigration: the immigration rate it defined as the ratio of the number of immigrants present in the population at time t + 1 and the total breeding population in year t, and πt , the proportion of immigrants among new recruits (i.e. new breeders). Two recently developed methods are likely to provide the most valuable data on immigration in the near future: individual parentage (rather than population) assignments based on genetic sampling, and spatially explicit integrated population models combining multiple sources of demographic data (survival, fecundity and population counts). Second, we report on a systematic literature review of studies providing a quantitative measure of immigration. Although the diversity of methods employed precludes detailed analyses, it appears that the number of immigrants exceeds locally born individuals in recruitment for most avian populations (median πt  = 0.57, N = 45 estimates from 37 studies), a figure twofold higher than estimated for mammalian populations (median πt  = 0.26, N = 33 estimates from 11 studies). Third, recent quantitative studies reveal that immigration can be the main driver of temporal variation in population growth rates, across a wide array of demographic and spatial contexts. To what extent immigration acts as a regulatory process has however been considered only rarely to date and deserves more attention. Overall, it is likely that most populations benefit from immigrants without necessarily being sink populations. Furthermore, we suggest that quantitative estimates of immigration should be core to future demographic studies and plead for more empirical evidence about the ways in which immigration interacts with local demographic processes to shape population dynamics. Finally, we discuss how to tackle spatial population dynamics by exploring, beyond the classical source-sink framework, the extent to which populations exchange individuals according to spatial scale and type of population distribution throughout the landscape.

Do you let me symptomatize? The potential role of cultural values in cross-national variability of mental disorders' prevalence.

BACKGROUND: Mental disorders may show inherent cross-national variability in their prevalence. A considerable number of meta-analyses attribute this heterogeneity to the methodological diversity in published epidemiological studies. Cultural values are characteristically not assessed in meta-regression models as potential covariates. AIM: Our aim was to conduct a meta-regression analysis to explore to what extent certain cultural values and immigration rates (as indicator of cultural diversity) might be associated with the cross-national heterogeneity of prevalence rates. METHOD: To minimize methodological differences that may exert a confounding effect, prevalence rates were obtained from the World Health Organization's (WHO) World Mental Health Survey Initiative. Cultural indices (overall emancipative values; overall secular values) were collected from the World Value Survey, while immigration rates were registered by utilizing the data of the United Nations' World Population Policies 2005 report. RESULTS: Meta-regression analysis indicated that overall emancipative values (i.e. promoting self-expression, non-violent protest) showed significant connection with lifetime and last year prevalence of any mood disorders (Z = 4.71, p = .001; Z = 2.35, p = .02) and any internalizing disorders (a merged category that combined mood and anxiety disorders; Z = 2.82, p = .004; Z = 2.34, p = .02). Overall secular values (i.e. rejecting authority and obedience) were negatively associated with last year prevalence of depression (Z = -2.75, p = .06). Multistep regression analysis indicated that immigration rate moderated the connection between cultural values and mental disorders. Countries with higher immigration rates showed higher emancipative and secular values. CONCLUSION: Our findings might function as potential foundation for formulating hypotheses regarding the cultural context's influence on the population's mental health.

Dosage consistency is the key factor in avoiding evolution of resistance to phosphine and population increase in stored-grain pests.

BACKGROUND: Control of pests in stored grain and the evolution of resistance to pesticides are serious problems worldwide. A stochastic individual-based two-locus model was used to investigate the impact of two important issues, the consistency of pesticide dosage through the storage facility and the immigration rate of the adult pest, on overall population control and avoidance of evolution of resistance to the fumigant phosphine in an important pest of stored grain, the lesser grain borer. RESULTS: A very consistent dosage maintained good control for all immigration rates, while an inconsistent dosage failed to maintain control in all cases. At intermediate dosage consistency, immigration rate became a critical factor in whether control was maintained or resistance emerged. CONCLUSION: Achieving a consistent fumigant dosage is a key factor in avoiding evolution of resistance to phosphine and maintaining control of populations of stored-grain pests; when the dosage achieved is very inconsistent, there is likely to be a problem regardless of immigration rate.