Trend analysis of the current epidemic situation and analysis of factors underlying local uneven spread of covid cases

This research has been carried out by analyzing the specific processes of the local epidemic dynamics of COVID by comparing the qualitative differences in fluctuations in 2020 and 2023. Methods of nonlinear dynamics of the development of epidemic processes in a rapidly changing situation were used to identify and qualify trends and unique situations that sometimes changed extremely fast. A distinctive feature of the modern pandemic is a rather sharp change in local trends: the effect of the fading of the primary outbreak of the disease and the sudden sharp onset of a new epidemic wave after a long trend of decreasing daily infections. Minimization of the exposure to viral infections did not prevent spreading the virus but created the illusion of success. The existing experience in generating forecasts of epidemic outbreaks based on models of past epidemic processes could not help when faced with a new evolving virus. The previously obtained understanding of the development and completion of epidemic processes of influenza virus strains more likely hindered the prediction of the scenario for the completion of the spread of a new infection, which is also associated with the eventual nature of the process and a variety of dynamic situations. A victory over COVID in the phase of the minimum after the wave, which was announced by many countries, turned out to be premature. New Zealand and Japan, which opted for a strict lockdown strategy in 2020, had a surge of COVID cases in early 2023 because new strains came into circulation. Outbreaks of respiratory diseases known as the Spanish flu and swine flu pandemics, data from which were used by many countries to make predictions, had run their course naturally in two or three waves of illness. At the beginning of 2023, against the backdrop of a global positive trend, some countries have reported a record rise in both mortality and daily morbidity due to the emergence of locally circulating “alarm” strains. A current stage on isolation of stable regional strains substantiates the classification of a series of differentiated properties of the dynamics of regional epidemic situations. Among the observed epidemic effects, extreme phenomena in the form of instantaneous bifurcation destruction of established regimes such as a sharp transition from long-term damped oscillations to a new exponential outbreak in some infections are separately highlighted. The selected options for the development of epidemic transient oscillatory processes are separately introduced in equation forms with delay for local epidemic trends. Equations are proposed to describe three variants of development of the observed stages of local epidemics. The task of constructing a generalized predictive model of a pandemic to describe interrelated regional processes at this stage seems insoluble.

epidemic waves, features of regional epidemics, oscillation decay scenarios, Coronavirus evolution, equations with delay, bifurcations of oscillatory regimes, factors of subpopulation immune resistance to COVID