Epidemic Process Research Articles

Quantum-Like Approaches Unveil the Intrinsic Limits of Predictability in Compartmental Models.

Obtaining accurate forecasts for the evolution of epidemic outbreaks from deterministic compartmental models represents a major theoretical challenge. Recently, it has been shown that these models typically exhibit trajectory degeneracy, as different sets of epidemiological parameters yield comparable predictions at early stages of the outbreak but disparate future epidemic scenarios. In this study, we use the Doi-Peliti approach and extend the classical deterministic compartmental models to a quantum-like formalism to explore whether the uncertainty of epidemic forecasts is also shaped by the stochastic nature of epidemic processes. This approach allows us to obtain a probabilistic ensemble of trajectories, revealing that epidemic uncertainty is not uniform across time, being maximal around the epidemic peak and vanishing at both early and very late stages of the outbreak. Therefore, our results show that, independently of the models' complexity, the stochasticity of contagion and recovery processes poses a natural constraint for the uncertainty of epidemic forecasts.

COVID-19 Modeling: A Review

The SARS-CoV-2 viruses and their triggered COVID-19 pandemic have fundamentally reshaped the world in almost every aspect, their evolution and influences remain. While over a million of literature have been produced on these unprecedented, overwhelming global disaster, one critical question is open: How has COVID-19 been quantified globally? This further inspires many other questions: What COVID-19 problems have been modeled? How have modeling methods in areas such as epidemiology, artificial intelligence (AI), data science, machine learning, deep learning, mathematics and social science played their roles in characterizing COVID-19? Where are the gaps and issues of these COVID-19 modeling studies? What are the lessons for quantifying future disasters? Answering these questions involves the analysis of a very broad spectrum of literature across different disciplines and domains. Distinguishing from specific efforts, this review takes the first attempt to generate a systematic, structured and contrastive landscape and taxonomy of global COVID-19 modeling. First, the surveyed problems span over a full range of COVID-19, including epidemic transmission processes, case identification and tracing, infection diagnosis and medical treatments, non-pharmaceutical interventions and their influence, drug and vaccine development, psychological, economic and social influence and impact, and misinformation, and so on. Second, the reviewed modeling methods traverse all relevant disciplines, from statistic modeling to epidemic modeling, medical analysis, biomedical analysis, AI, deep and machine learning, analytics, and simulation. Critical analyses further identify significant issues and gaps, for example, simple techniques and similar problems have been overwhelmingly addressed everywhere, while intrinsic and foundational issues and deep insights have been overlooked. The review discloses significant opportunities for more deeply, effectively and uniquely quantifying COVID-19-like global disasters from their intrinsic working mechanisms, interactions and dynamics.

The optimal spatially-dependent control measures to effectively and economically eliminate emerging infectious diseases.

Non-pharmaceutical interventions (NPIs) are effective in mitigating infections during the early stages of an infectious disease outbreak. However, these measures incur significant economic and livelihood costs. To address this, we developed an optimal control framework aimed at identifying strategies that minimize such costs while ensuring full control of a cross-regional outbreak of emerging infectious diseases. Our approach uses a spatial SEIR model with interventions for the epidemic process, and incorporates population flow in a gravity model dependent on gross domestic product (GDP) and geographical distance. We applied this framework to identify an optimal control strategy for the COVID-19 outbreak caused by the Delta variant in Xi'an City, Shaanxi, China, between December 2021 and January 2022. The model was parameterized by fitting it to daily case data from each district of Xi'an City. Our findings indicate that an increase in the basic reproduction number, the latent period or the infectious period leads to a prolonged outbreak and a larger final size. This indicates that diseases with greater transmissibility are more challenging and costly to control, and so it is important for governments to quickly identify cases and implement control strategies. Indeed, the optimal control strategy we identified suggests that more costly control measures should be implemented as soon as they are deemed necessary. Our results demonstrate that optimal control regimes exhibit spatial, economic, and population heterogeneity. More populated and economically developed regions require a robust regular surveillance mechanism to ensure timely detection and control of imported infections. Regions with higher GDP tend to experience larger-scale epidemics and, consequently, require higher control costs. Notably, our proposed optimal strategy significantly reduced costs compared to the actual expenditures for the Xi'an outbreak.

Ecological and epidemiological characteristics of tick-borne encephalitis and ixodic tick-borne borreliosis incidence according to the data of the Arkhangelsk region for 2012–2022

BACKGROUND: The increase of ticks infected with borrelia and tick-borne encephalitis virus, as well as the impact of anthropogenic factor on the ecosystem of the northern region determines the need to study possible risk factors and epidemiological trends in the incidence of tick-borne encephalitis and ixoid tick-borreliosis. AIM: To conduct a retrospective ecological and epidemiological analysis of regional peculiarities of the epidemic process of tick-borne encephalitis and ixoid tick-borreliosis in the Arkhangelsk region in comparison with similar indicators in the North-West Federal District and Russia for 2012–2022. MATERIALS AND METHODS: The work was carried out in accordance with the ecological research design. Statistical data of the Unified Interdepartmental Information and Statistical System, as well as statistical annual forms of the Department of the Federal Service for Supervision of Consumer Rights Protection and Human Welfare in Russia and the Arkhangelsk region were used as the information base. The registered cases of tick-borne encephalitis and ixoid tick-borreliosis morbidity in the Arkhangelsk region, as well as in Russia and the Northwestern Federal District as a whole for 2012–2022 were evaluated. Time series analysis was performed using Microsoft Excel 2019. The study also analyzes the dynamics of climatic factors in the Arkhangelsk region and its possible impact on the distribution and migration of ixodid ticks across the territory of the European North of Russia. Correlations were assessed by evaluating Pearson’s correlation criterion using the Google Collaboratory interface. RESULTS: The number of tick bites in the Arkhangelsk region throughout the entire study period significantly exceeds the similar indicator (per 100 thousand population) in Russia. The incidence of tick-borne encephalitis in the Arkhangelsk region significantly exceeds that in both the Russian Federation and the Northwestern Federal District, and exceeded the average annual rate in Russia more than 3 times, although it had a faster rate of decline (5.7% vs. 3.7% annually). The incidence of ixoid tick-borreliosis has a paradoxical character due to the fact that throughout almost the whole period it is below the all-Russian level (3.19 per 100,000 population in Arkhangelsk region against 4.41 in the Russian Federation), while the incidence in the Northwestern Federal District is 1.3 times higher on average. CONCLUSIONS: During the last decade the incidence of tick-borne encephalitis in the Arkhangelsk region remains stably high in comparison with both the Russian Federation and the Northwestern Federal District. The incidence of ixoid tick-borreliosis corresponds to the long-term average for Russia, with a more pronounced downward trend (4.7% vs. 1.7%). The territory of the Arkhangelsk region is subject to the trend of increasing average annual temperatures, and anthropogenic interventions, in particular, abundant deforestation, lead to the destruction of established ecosystems and open new opportunities and territories for ticks, which in the future may negatively affect the established trends of morbidity. The analysis confirms the need to develop and adopt organizational measures aimed at the development of epidemiological and epizootological monitoring.

Vaccination subsidy allocation under budget constraints considering the human interpersonal contact pattern and vaccine protection effect in epidemics

Vaccination subsidy is one of the most important measures to increase the willingness of people to be vaccinated for epidemic prevention and control. Given the budget constraint of vaccination subsidy and the different roles of various age groups population in the epidemic transmission process, a novel approach is proposed to optimize the utilization of the limited vaccination subsidy budget. First, an age-structured SIR model that integrates the human interpersonal contact pattern and vaccine protection effect is developed to simulate the epidemic trend under a certain vaccination state. Then, a decision model is constructed to determine the optimal vaccination subsidy allocation scheme for various age groups based on the age-structured SIR model. A case study of Wuhan City is used to verify the decision approach, and a series of sensitivity analyses are conducted. The result shows that the peak time of an epidemic is positively related to the total treatment cost for all the infections, and more subsidies should be allocated to the populations with higher interpersonal contact frequencies for epidemic prevention and control.

Risk groups of HIV infection among the population of the Omsk region

The peculiarities of the course of the epidemic process of HIV infection, including the formation of certain risk groups by gender, age and social status, are relevant, as they allow the development of specific preventive measures. The aim is to identify risk groups for HIV infection among the population of the Omsk region in 1996–2023. Data from the main statistical reporting forms, the Federal Register of Persons Infected with the Human Immunodeficiency Virus, and the results of epidemiological investigations were used for the analysis. The analysis made it possible to establish the main trends in the development of the epidemic process of HIV infection in the Omsk region. The general trend of decreasing morbidity has been revealed, which coincides with that in the Russian Federation, primarily due to the large volume of preventive measures carried out. Changes in the characteristics of the risk groups of infection have been established — the contingents of injecting drug users and men who have sex with men, prevailing at an early stage of the epidemic, have been replaced by persons who became sexually infected from individuals of the opposite sex. At the same time, the proportion of infected women approached that of men. This entailed the risk of perinatal transmission of HIV infection. The introduction of mandatory screening for HIV infection markers in pregnant women and the implementation of antiretroviral prophylaxis has reduced the number of cases of perinatal infection of newborns to a minimum. An increase in the share of the rural population in the total structure of newly diagnosed people with HIV infection may indicate both lower awareness of this problem and shortcomings in the provision of medical care, its lower accessibility compared to the urban population. The prevalence in the structure of HIV-infected people who are not engaged in work indicates that the most socially unprotected contingents are involved in the epidemic process, as a rule, they are not ready to take care of their own health and the health of others, often leading an antisocial lifestyle. Thus, HIV infection in the Omsk region remains one of the priority epidemiological problems requiring the formation of an integrated approach to its solution. The conducted research made it possible to identify the main risk groups for HIV infection, in relation to which targeted preventive strategies should be applied.

Measles in the elimination period: the epidemic situation in Voronezh region

Vaccine-preventable diseases, one of which is measles, do not lose their importance and still remain a threat to public health. There is a deterioration in the epidemic situation regarding measles, both in the world and in the Russian Federation. The purpose of the study was to characterize the manifestations of the measles epidemic process in the Voronezh region for the period 1940–2023. The study of morbidity was carried out on the basis of data from Rosstat Form 2, 146 maps of the epidemiological investigation of a case of measles in the Voronezh region for the period 2011–2023 with the calculation of basic statistical indicators. The general availability of effective measles vaccination led to a decrease in the incidence, which by the beginning of the 21st century had become sporadic. However, from 2011 to 2023, there is an upward trend in incidence: rates increased from 0.27 cases (95 % CI 0.06–0.48) to 2.14 per 100 thousand population (95 % CI: 1.54–2,74); the risk group were children (average age 5.70 ± 0.24 years). From 2011 to 2015 imported cases predominated; since 2016 local cases predominated. For 2011–2023 146 cases (81 outbreaks) of measles were registered; among those who fell ill, the majority were not vaccinated against this infection or did not know about their vaccination status. Seroprotection level for the period 2011–2023 averaged 94.09±0.41 %; in certain years, there was an insufficient level of the immune layer in indicator groups of the population 16–17 years old and older. Thus, the pronounced activation of the measles epidemic process in the Voronezh region in recent years is due to a decrease in the immune layer.

Asymptotic distribution of the final size of a stochastic SIR epidemic on heterogeneous networks

In this paper, a Markovian SIR model on a heterogeneous network is considered. The law of large numbers and the central limit theorem of the epidemic process in a large population are provided. Further, the asymptotic distribution of the final size is given. Finally, by numerical and stochastic simulations, it is clear to show that our method performs well in approximation.

Modern epidemiological features of viral acute intestinal infections in children and adolescents of Sakhalin region

Objective: to identify modern epidemiological features of viral acute intestinal infections in children and adolescents in the Sakhalin Region.Materials and methods. Data on acute intestinal infection incidence obtained from statistical reports of the Rospotrebnadzor during 2021-2023 was compared with long-term average incidence rates calculated over the period before the COVID-19 pandemic (2010-2019) to perform epidemiological analysis. Incidence was calculated for different age groups; according to months of the year, monthly long-term average incidence rates were established. Index of seasonality, coefficient of seasonality, and index of seasonal growth were determined.Results and discussion. Manifestations of acute intestinal infections epidemic process in the Sakhalin Region indicate persisting conditions for an increase in the registration of both sporadic cases of diseases and outbreaks of infectious diarrhea. Viruses were prevailing in the structure of cases of known etiology (mainly caused by rotaviruses and noroviruses). Their intra-annual dynamics showed changes in rotavirus and norovirus infection incidence rates: a shift in periods of increased incidence, a decrease in the coefficient of seasonality, and for rotavirus infection, a decrease in the index of seasonal growth. Age-adjusted rotavirus infection incidence showed predominance of the infection among preschool-aged children; norovirus infection was frequently detected among schoolchildren and adolescents. An increase in the focality index may indicate ongoing problems in the public catering sector, non-compliance with sanitary rules and hygiene standards, and untimely detection and isolation of patients with acute intestinal infections.Conclusion. Obtained results confirm the epidemiological significance of viral gastroenteritis and the necessity of anti-epidemic measures optimization.

The role of mobility in epidemics near criticality

Abstract The general epidemic process (GEP), also known as susceptible-infected-recovered model, provides a minimal model of how an epidemic spreads within a population of susceptible individuals who acquire permanent immunization upon recovery. This model exhibits a second-order absorbing state phase transition, commonly studied assuming immobile healthy individuals. We investigate the impact of mobility on the scaling properties of disease spreading near the extinction threshold by introducing two generalizations of GEP, where the mobility of susceptible and recovered individuals is examined independently. In both cases, including mobility violates GEP’s rapidity reversal symmetry and alters the number of absorbing states. The critical dynamics of the models are analyzed through a perturbative renormalization group (RG) approach and large-scale stochastic simulations using a Gillespie algorithm. The RG analysis predicts both models to belong to the same novel universality class describing the critical dynamics of epidemic spreading when the infected individuals interact with a diffusive species and gain immunization upon recovery. At the associated RG fixed point, the immobile species decouples from the dynamics of the infected species, dominated by the coupling with the diffusive species. Numerical simulations in two dimensions affirm our RG results by identifying the same set of critical exponents for both models. Violation of the rapidity reversal symmetry is confirmed by breaking the associated hyperscaling relation. Our study underscores the significance of mobility in shaping population spreading dynamics near the extinction threshold.

Research on safety strategies for nucleic acid testing in sudden epidemic conditions based on a SEIARD dynamic model

Infectious diseases have caused enormous disasters in human society, and asymptomatic carriers are an important challenge in our epidemic prevention and control process. Nucleic acid testing has played an important role in rapid testing for asymptomatic individuals. How to carry out nucleic acid testing in a scientific manner is a practical problem encountered in normal production and life. Based on the real COVID-19 epidemic data from Shanghai, we established a susceptible-exposed-infected-asymptomatic-recovered-death (SEIARD) dynamic model. The least squares method was used to fit the data and estimate the unknown parameters β and E(0) in the model, and MATLAB software was employed to simulate the development of the epidemic. The data fitting results indicated that the SEIARD model can better describe the early development patterns of the epidemic (R2 = 0.98; MAPE = 2.54%). We calculated the basic reproduction number of the Shanghai epidemic as R0 = 2.86. As the frequency of nucleic acid testing increased, the basic reproduction number R0 continued to decrease. When there is one latent carrier and one asymptomatic carrier in the nucleic acid testing team, the number of queues is directly proportional to the number of infected individuals, the nucleic acid testing team increases by 50 people, and the number of new asymptomatic cases increases by approximately 4 people. If both susceptible individuals (S) and asymptomatic patients (A) are not wearing masks, the infection rate reaches approximately 7%; after wearing masks, the final infection rate is less than 1% at 1.5 m between two people. The queue spacing is inversely proportional to the number of infected individuals. With a distance of d = 1 m, a nucleic acid testing team of 100 people added 8% of the infected individuals; when d = 1.5 m, fewer than 2% of the newly infected individuals. The results confirmed that controlling the queue size for nucleic acid testing, strictly wearing masks, and maintaining a queue spacing of more than 1.5 m are safe and effective nucleic acid testing strategies. Our findings are also applicable to the prevention of other newly emerging infectious diseases.

Modeling of Throbbing Invasive and Epidemic Processes Based on Biophysical Adaptation Hybrid Structures

Modeling of Throbbing Invasive and Epidemic Processes Based on Biophysical Adaptation Hybrid Structures

Limitations in creating artificial populations in agent-based epidemic modeling: a systematic review

Introduction. The key step in agent-based modeling of epidemics, which allows researchers to take into account individual characteristics of people, is the creation of an artificial population. The main difficulty of this procedure is finding a balance between the detail of the population description and the computational efficiency of the calculations. The aim and objectives of the review: Critically analyze and summarize the current evidence on how to create artificial populations; evaluate the limitations and advantages of available approaches in solving various problems in epidemiology. Materials and methods. An analysis of literature sources devoted to agent-based modeling has been performed. The analysis is focused on algorithms for creating an artificial population with a given level of detail for modeling human respiratory infections. Results. The approaches to the creation of artificial populations are generalized. The main principles of realization of interaction between agents are revealed: by means of networks of contacts between agents and on the basis of taking into account the movement of agents between locations. The first approach is the most computationally efficient and simple; the second approach allows to better take into account the change in the behavior of agents during the development of the epidemic process. Conclusion. Agent-based modeling is an optimal tool for selecting the best scenario for epidemic control and investigating the role of individual characteristics of people in the development of epidemics. When creating an artificial population, it is important to include in the model factors that can be targeted for control. A significant limitation is the lack of factual data on population structure, but this can be overcome by using indirect data.

Epidemiologic Monitoring of Enterovirus (Nepolio) Infection: Rationale for Improvement

Relevance. Non-polio enteroviruses are widespread worldwide, with millions of cases being reported each year, but limited data exist on the true burden of enterovirus (non-polio) infections (EVnI) worldwide due to a lack of standardized surveillance. Considering the absence of specific prevention of EnVI and the difficulty of predicting the epidemic situation due to the diversity of types of enteroviruses, there is an obvious need for substantiating and supplementing the existing parameters of epidemiological monitoring, identifying additional indicators of morbidity risk for the purpose of timely implementing preventive and anti-epidemic measures. Aim. Rationale of necessity of additional measures of the EVnI observation for early discovery of the activation of the epidemic process. Materials and methods. The research was held during the year 2023 and included the following three components: 1. The prospective continuous observation of the patients ranging from 0 to 18 years old who received medical help in ambulatory conditions. Possible symptoms of EVnI were studied using the ambulatory diseased person’s medical cards (f. № 0/25у). 2. The research of biological material, which belonged to the healthy people and people with signs of probable EVnI. 3. The study of epidemiological connection of dew point temperature with the manifestations of the EVnI epidemic process. Results. Probable clinical symptoms of EVnI are found among 511 observed children. Positive correlational connection with EVnI is visible among exanthems (0,43, p < 0,001) and acute nasopharyngitis (0,13, p < 0,001). The maximal incidence rate of EVnI is discovered in a period from 27th to 36th week (54,35 ‰), which coincides with maximal incidence rate of acute nasopharyngitis (434,78 ‰). The rise in incidence rate of EVnI in comparison to the last period is 4,45 times (p < 0,001), while in comparison to the rise in incidence rate of acute nasopharyngitis is 2,71 times (p < 0,0001). In planned observation of examined patients with probable symptoms, EVnI disease is found amongst 78 people, the incidence rate made 254,07 ‰ and that aligns with the results of active observation of health center appeals (267,68 ‰, p > 0,99). Clinical diagnosis of EVnI is made only in 51,28 %% of all cases. As a result of ill and healthy people’s observation, their relation is found to be 6:1 respectively. The activation of the epidemic process started in concurrence with dew point temperature +4,85 °C and continued until the dew point temperature +20,33 °C. Conclusion. The existing system of epidemiological supervision over EVnI has to be enhanced by adding the research on NPEV among the people who have acute nasopharyngitis during the stable rise in dew point temperature from +5,0 °C. Taking into account the rise in the incidence rate of EVnI, it is reasonable to expand the microbiological observation of biological material which belongs to the people who have exanthems, diarrheal syndrome and healthy people

Epidemiological features and psychoneurological consequences of infection of people with the Nipah virus

The lecture outlines modern ideas about the etiology, features of the epidemic process, mechanisms of damage to the human body, clinical manifestations, diagnosis, treatment and prevention of infection caused by the Nipah virus. Particular attention is paid to the characteristics of individual outbreaks of the infectious process in various geographical regions of the world, early and long-term psychopathological, neurological and cognitive consequences due to human infection with the Nipah virus. The risk factors for the emergence and rapid spread of infection with a very high mortality rate, reaching 100%, are emphasized, which determines the high pandemic potential and hidden threats to human society. Recommendations are outlined for the prevention of transmission of infection caused by the Nipah virus at all levels: from animals to humans, from humans to humans, in medical institutions, which, in the absence of effective vaccine prevention and specific antiviral treatment, are the basis for containing the spread of the infectious process. In this regard, measures taken and planned to provide patients and contact persons with adequate medical and psychological care, features of the development and implementation of effective anti-epidemic, clinical diagnostic algorithms, timely and high-quality social and hygienic monitoring of environmental objects against the backdrop of increasing biological threats from outside, and within the country will minimize the risks of biological threats. The lecture is intended for doctors of various specialties, including infectious disease specialists, epidemiologists, general practitioners, neurologists, psychiatrists, laboratory diagnosticians, radiologists etc.

Оценка многолетней динамики заболеваемости корью

The paper examines the relevance of the measles problem in the Russian Federation, Volga Federal District, and Orenburg Region among various age groups. The manifestations of the measles epidemic process in long-term dynamics from 2010 to 2022 were studied and analyzed. A retrospective epidemiological analysis of the incidence of measles in the population was carried out, including an analysis of the long-term dynamics of the incidence of the population, an analysis of the intra-annual dynamics of the incidence and an analysis of the long-term dynamics of the incidence among various population groups. It has been established that the long-term average incidence of measles in the Orenburg region exceeds that in the Volga Federal District. Areas at risk for measles incidence among municipalities of the Orenburg region are Sorochinsky and Tashlinsky districts. The risk group for measles incidence in the Orenburg region is the child population. Two full cycles of rise and fall in morbidity have been established. In the intra-annual dynamics of the incidence of whooping cough, spring-winter seasonality is noted. Keywords: measles, retrospective epidemiological analysis, risk areas, risk groups, time of risk, incidence.

Competitive networked bi-virus spread: Existence of coexistence equilibria

The paper studies multi-competitive continuous-time epidemic processes. We consider the setting where two viruses are simultaneously prevalent, and the spread occurs due to individual-to-individual interaction. In such a setting, an individual is either not affected by any of the viruses, or infected by one and exactly one of the two viruses. One of the equilibrium points is the coexistence equilibrium, i.e., multiple viruses simultaneously infect separate fractions of the population. We provide a sufficient condition for the existence of a coexistence equilibrium. We identify a condition such that for certain pairs of spread matrices either every coexistence equilibrium lies on a line that is locally exponentially attractive, or there is no coexistence equilibrium. We then provide a condition that, for certain pairs of spread matrices, rules out the possibility of the existence of a coexistence equilibrium, and, as a consequence, establishes global asymptotic convergence to the endemic equilibrium of the dominant virus. Finally, we provide a mitigation strategy that employs one virus to ensure that the other virus is eradicated. The theoretical results are illustrated using simulations.

Determination of the immune response type in measles patients of different ages from a high-incidence area

According to the WHO data, the incidence of measles is now in the cyclic increase phase. The non-vaccinated subjects, like as persons who have previously received one or two doses of measles vaccine are involved in the epidemic process. The purpose of our study was to determine the immunological pattern in the groups of measles patients of different age in areas with high incidence of infection. To determine the immune response type in measles patients, qualitative and quantitative indices of IgM and IgG were used, detected by the following ELISA test-systems: VectoMeasles-IgM (JSC “Vector-Best”, Russia); Anti-Measles Viruses ELISA (IgG) and Avidity Anti-Measles Viruses ELISA IgG (Euroimmun, Germany). The serological study of 1893 patient allowed to determine the primary and secondary types of immune response. In 72.64% of the patients with primary immune response, the serum samples contained low-avidity IgG at a concentration of 0.45 (0.22- 0.74) IU/mL. In the group with a secondary immune response, high-avidity antibodies were detected at a concentration of 24.28 (21.59-27.4) IU/mL. The antibody levels in secondary type of response was 54-fold higher than IgG values in the first group (p 0.05). In the group with primary immune response, the ratio of children ( 1 to 14 years) and adults (18 to 70 years old) was almost the same (49.6% and 47.56%). Appropriate values for children and adult cohorts with a secondary immune response were 2.12% and 96.53%, respectively (p 0.05). Among 46 teenagers (15-17 years old), 84.8% responded with a primary immune response to the measles virus. Thus, in the area with high-incidence of measles among patients of different age, the primary-type immune response was determined in 72.64%, and secondary-type, in 27.36%. We have found that in the patients with a secondary type of immune response group, the proportion of children and teenagers was 27.8 times lower than among adults, thus indicating to high efficiency of vaccination in pediatric population. At the same time, the results of studies among measles patients with primary-type immune response, both children and adults, suggest some “gaps” in the vaccine prevention program.

Dynamics of a susceptible-infected-recovered model on complex networks with interregional migration.

We present a susceptible-infected-recovered model based on a dynamic flow network that describes the epidemic process on complex metapopulation networks. This model views population regions as interconnected nodes and describes the evolution of each region using a system of differential equations. The next-generation matrix method is used to derive the global basic reproduction number for three cases: a general network with homogeneous infection rates in all regions, a fully connected network, and a star network with heterogeneous infection and recovery rates. For the homogeneous case, we show that this global basic reproduction number is independent of the migration rates between regions. However, the rate of convergence of each region to an equilibrium state exhibits a much larger variance in random (Erdős-Rényi) networks compared to small-scale (Barabási-Albert) networks. For the general heterogeneous case, we report interesting results, namely that the global basic reproduction number decays exponentially with respect to the smallest nonzero Laplacian eigenvalue (algebraic connectivity). Furthermore, we demonstrate both analytically and numerically that as the network's algebraic connectivity increases, either by increasing the average node degree of each region or the global migration rate, the global basic reproduction number decreases and converges to the ratio of the average local infection rate to the average local recovery rate, meaning that the lower bound of the global basic reproduction rate does not equal the mean of local basic reproduction rates.

Epidemiological characteristics of measles in the Ryazan region in 2000–2023: current trends and unresolved problems

The aim of the work was to analyze and identify the features of the epidemic process of measles in the Ryazan region in 2000–2023. Based on the study of materials from state reports «On the state of sanitary and epidemiological welfare of the population.» It was found that there was no constant circulation of the measles virus in the Ryazan region in 2000–2023. There have been periodic increases in morbidity due to the importation of the pathogen with its subsequent spread among unvaccinated individuals. The main reasons for the deterioration of the epidemic situation were errors in the immunoprophylaxis of the population, mainly associated with refusals of preventive vaccinations and violation of immunization schemes during the COVID-19 pandemic. Taking into account the identified features, a set of measures aimed at achieving the elimination of measles in the studied region is proposed.