Territorial Strategy of Medical Units for Addressing the First Wave of the COVID-19 Pandemic in the Metropolitan Area of Mexico City: Analysis of Mobility, Accessibility and Marginalization

Background. The COVID-19 pandemic has caused an exponential increase in the demand for medical care worldwide. In Mexico, the COVID Medical Units (CMUs) conversion strategy was implemented. Objective. To evaluate the CMU coverage strategy in the Mexico City Metropolitan Area (MCMA) by territory. Materials. The CMU directory was used, as were COVID-19 infection and mobility statistics and Mexican 2020 census information at the urban geographic area scale. The degree of urban marginalization by geographic area was also considered. Method. Using descriptive statistics and the calculation of a CMU accessibility index, population aggregates were counted based on coverage radii. In addition, two regression models are proposed to explain (1) the territorial and temporal trend of COVID-19 infections in the MCMA and (2) the mobility of the COVID-infected population visiting medical units. Results. The findings of the evaluation of the CMU strategy were (1) in the MCMA, COVID-19 followed a pattern of contagion from the urban center to the periphery; (2) given the growth in the number of cases and the overload of medical units, the population traveled greater distances to seek medical care; (3) after the CMU strategy was evaluated at the territory level, it was found that 9 out of 10 inhabitants had a CMU located approximately 7 km away; and (4) at the metropolitan level, the lowest level of accessibility to the CMU was recorded for the population with the highest levels of marginalization, i.e., those residing in the urban periphery.

Territorial strategy of medical units for addressing the COVID-19 pandemic in the metropolitan area of Mexico City: analysis of mobility, accessibility and marginalization

The COVID-19 pandemic has caused an exponential increase in the demand for medical care worldwide. In Mexico, the COVID Medical Units (CMU) conversion strategy was implemented. Objective. To evaluate the CMU coverage strategy in the Mexico City Metropolitan Area (MCMA) by territory. Materials. The CMU directory was used, as were COVID-19 infection and movement statistics and 2020 Mexican census information at the urban geographic area scale. The degree of urban marginalization by geographic area was also considered. Method. Using descriptive statistics and the calculation of a CMU accessibility index, population aggregates were counted based on coverage radii. In addition, two regression models are proposed to explain 1) the territorial and temporal trend of COVID-19 infections in the MCMA and 2) the movement of the COVID-infected population to medical units. Results. The findings of the evaluation of the CMU strategy were 1) in the MCMA, COVID-19 followed a pattern of contagion from the urban center to the periphery; 2) given the growth in the number of cases and the overload of medical units, the population traveled greater distances to seek medical care; 3) after the CMU strategy was evaluated at the territory level, it was found that 9 out of 10 inhabitants had a CMU located approximately 7 kilometers away; and 4) at the metropolitan level, the lowest level of accessibility to the CMU was recorded for the population with the highest levels of marginalization: those residing in the urban periphery.

The Influence of Competition Trait-Mediated Effects on Intra-Guild Predation System

Parasitism can affect the population dynamics in many ways, and its indirect effect is easy to be ignored, that is, it can weaken the host's behavior, physiology and psychology to affect the whole population. In this paper, we build a differential equation model by adding four parameters to study the influence of multiple competitive relationships on the predator-prey system, It includes the enhancement effect g of intraspecific competition and the enhancement effect h of interspecific competition between susceptible population and infected population, the weakening effect m of intraspecific competition and the weakening effect n of interspecific competition between susceptible population and infected population. Through the analysis, it can be concluded that a single g or m can promote the symbiosis of predator and prey, a single h has little effect on the population dynamics, and a single n is not conducive to the symbiosis; The fusion of g and h promotes coexistence, but the fusion of m and n is on the contrary; Interestingly, the combination of multiple regulatory parameters has a chemical effect on the survival of species, but the combination of g, m and h can inhibit coexistence, while the combination of g, m and n can promote coexistence. The reason is that the combination of parameters is not a simple addition of effects, but a prerequisite for mutual influence. To sum up, the research content provides a reference for considering the role of multiple factors, and provides theoretical guidance for explaining ecological phenomena and proving ecological conclusions.

Safety and humoral responses to BNT162b2 mRNA vaccination of SARS-CoV-2 previously infected and naive populations

Since COVID-19 risk of reinfection is of great concern, the safety and efficacy of the mRNA-based vaccines in previously infected populations should be assessed. We studied 78 individuals previously infected with SARS-CoV-19, who received a single dose of BNT162b2 mRNA COVID-19 vaccine, and 1:2 ratio matched infection-naïve cohort who received two injections. The evaluation procedure included symptom monitoring, and serological tests. Among the post-infected population, the median IgG-S response after the first vaccine dose was 3.35 AU, compared to 2.38 AU after the second vaccine injection in the infection naive group. A strong correlation was demonstrated between IgG-S level before vaccination, and the corresponding responses after a single vaccine dose (r = 0.8, p < 0.001) in the post infected population. Short-term severe symptoms that required medical attention were found in 6.8% among the post-infected individuals, while none were found in the infection naïve population. Our data suggest that a single vaccine dose is sufficient to induce an intense immune response in post-infected population regardless of seropositivity. Although some short-term safety issues were observed compared to the infection naïve population, a single dose regimen can be considered safe in post-infected populations.

Multiple Outbreaks Resulting from Asymptomatic Infection in Spreading of COVID-19

In this paper, we establish a compartmental model for the transmission of COVID-19 with both symptomatic and asymptomatic infections. The difference is that in our model, we consider the infection caused by multiple contacts with asymptomatic infected population. Through the dynamic analysis of the model, we found that when there is only one contact with an asymptomatic infected people, the system has a unique threshold to control the disease. When there is two contact with asymptomatic infected population, the system will undergo forward bifurcation, backward bifurcation, saddle-node bifurcation, supercritical Hopf bifurcation, subcritical Hopf bifurcation, and Bogdanov-Takens bifurcation with codimension 2. Finally, we give The complete bifurcation diagram and global phase diagram of the system, and the biological significance of our results are also given.

Humoral and cellular immune response to Plasmodium vivax VIR recombinant and synthetic antigens in individuals naturally exposed to P. vivax in the Republic of Korea

Background Plasmodium vivax proteins with variant interspersed repeats (VIR) are the key proteins used by the parasite to escape from the host immune system through the creation of antigenic variations. However, few studies have been done to elucidate their role as targets of immunity. Thus, this study evaluated the naturally-acquired immune response against VIR proteins in vivax malaria-infected individuals in the Republic of Korea (ROK). Methods Seven recombinant VIR proteins and two synthetic peptides previously studied in other countries that elicited a robust immune response were used to investigate the antibody and cellular immune response in 681 P. vivax-infected people in ROK. The expression of IgM, IgG, and IgG subclasses against each VIR antigen or against PvMSP1-19 was analysed by ELISA. PvMSP1-19, known as a promising vaccine candidate of P. vivax, was used as the positive control for immune response assessment. Furthermore, the cellular immune response to VIR antigens was evaluated by in vitro proliferative assay, cellular activation assay, and cytokine detection in mononuclear cells of the P. vivax-infected population. Results IgM or IgG were detected in 52.4% of the population. Among all the VIR antigens, VIR25 elicited the highest humoral immune response in the whole population with IgG and IgM prevalence of 27.8% and 29.2%, respectively, while PvMSP1-19 elicited even higher prevalence (92%) of IgG in the population. As for the cellular immune response, VIR-C2, PvLP2, and PvMSP1-19 induced high cell activation and secretion of IL-2, IL-6, IL-10, and G-CSF in mononuclear cells from the P. vivax-infected population, comparable with results from PvMSP1-19. However, no significant proliferation response to these antigens was observed between the malaria-infected and healthy groups. Conclusion Moderate natural acquisition of antibody and cellular responses in P. vivax-infected Korean malaria patients presented here are similar to that in other countries. It is interesting that the immune response to VIR antigens is conserved among malaria parasites in different countries, considering that VIR genes are highly polymorphic. This thus warrants further studies to elucidate molecular mechanisms by which human elicit immune response to the malaria parasite VIR antigens.

An Extended Susceptible-Exposed-Infected-Recovered (SEIR) Model with Vaccination for Forecasting the COVID-19 Pandemic in Sri Lanka

The role of modelling in predicting the spread of an epidemic is important for health planning and policies. This study aims to apply a compartmental model for predicting the variations of epidemiological parameters in Sri Lanka. We used a dynamic Susceptible-Exposed-Infected-Recovered-Vaccinated (SEIRV) model, and simulated for potential vaccine strategies under a range of epidemic conditions. The predictions were based on different vaccination coverages (5% to 90%), vaccination-rates (1%, 2%, 5%) and vaccine-efficacies (40%, 60%, 80%) under different R0 (2,4,6). We observed how the above dynamics influenced the SEIRV model without COVID-19 vaccination at different R0 values, and estimated the duration, exposed and infected populations. When the R0 was increased, the days of reduction of susceptibility and the days to reach the peak of the infection were reduced gradually. At least 45% vaccine coverage is required for reducing the infected population as early as possible. The results revealed that when R0 is increased in the SEIRV model along with the increase of vaccination efficacy and vaccination rate, the population to be vaccinated is reducing. Thus, the vaccination offers greater benefits to the local population by reducing the time to reach the peak, exposed and infected population through flattening the curves.