Features of the COVID-19 Epidemic Process in Each of the of the Five Waves of Morbidity in Russia

Relevance. An assessment of the characteristics of the different phases of the COVID-19 pandemic is clearly of interest. Aim. To assess the intensity of the epidemic process in each of the five waves of COVID-19 in Russia. Materials and methods. The data on morbidity, hospitalization and deaths from COVID-19 of the population as a whole and by age groups from 48 (in the I rise) to 54 cities (in the V wave) and data from the website of the Russian consortium for sequencing coronavirus genomes were analyzed. Results. The nature of the course of the first 5 waves in the incidence of COVID-19 in Russia remains undulating. The waves in morbidity began in megacities, and the direction of spread across the FD differed in different waves of morbidity. The results of gene sequencing showed the participation of the main genovariants of the coronavirus in the etiology of diseases up to 3-4 waves. Some genovariants identified earlier received maximum distribution in the following wave. In Russia, the European descendants of the Wuhan strain (74.4%) were dominant in the I wave in morbidity, in the II wave – its daughter genovariants (68.5%), in the III – AY.122 (80.1%), in the IV – AY.122 (84.7%) and in the V wave – Omicron (76.7%). Conclusions. The features of each wave in the incidence of COVID-19 depended on the properties of the dominant genovariants: their ability to transmit from person to person and virulence. The rate of spread of the epidemic by FD, the susceptibility of all age groups and the intensity of epidemics were maximal during the period of the V wave in morbidity with the Omicron gene variant. Mortality was minimal in the I wave of morbidity, maximal in the IV with AY.122 strains and low in the V wave with Omicron genovariants. The influence of the season of the year was manifested in the summer season by an increase in the incidence of COVID-19 earlier in the Russian Federation as a whole (immediately after megacities) than in most federal districts, but with a lower incidence. © 2023, Numikom. All rights reserved.

M&A activity during the COVID-19 pandemic

We investigate whether the COVID-19 pandemic initiated merger waves at the aggregate and industry levels. The COVID-19 pandemic coincides with economic shocks, wide adoption of new technologies, and volatility in stock and energy markets, all potential triggers of restructuring activity. Our sample covers 104,464 acquisition deals of US targets from 2012 to 2022. We identify 37 industry-level merger waves. Twenty-three merger waves start during the COVID-19 pandemic. Eighty percent of the deals during the pandemic were part of an industry merger wave. This concentration of industry waves drove an aggregate merger wave starting on April 2020.

Interpersonal Distance Tracking with mmWave Radar and IMUs

Tracking interpersonal distances is essential for real-time social distancing management and ex-post contact tracing to prevent spreads of contagious diseases. Bluetooth neighbor discovery has been employed for such purposes in combating COVID-19, but does not provide satisfactory spatiotemporal resolutions. This paper presents ImmTrack, a system that uses a millimeter wave radar and exploits the inertial measurement data from user-carried smartphones or wearables to track interpersonal distances. By matching the movement traces reconstructed from the radar and inertial data, the pseudo identities of the inertial data can be transferred to the radar sensing results in the global coordinate system. The re-identified, radar-sensed movement trajectories are then used to track interpersonal distances. In a broader sense, ImmTrack is the first system that fuses data from millimeter wave radar and inertial measurement units for simultaneous user tracking and re-identification. Evaluation with up to 27 people in various indoor/outdoor environments shows ImmTrack's decimeters-seconds spatiotemporal accuracy in contact tracing, which is similar to that of the privacy-intrusive camera surveillance and significantly outperforms the Bluetooth neighbor discovery approach. © 2023 Owner/Author.

USES OF THE SKEW-LOGISTIC FUNCTION FOR MULTI-WAVE FUNCTIONS

The Skew-Logistic (SL) function has been proposed to model a real-life dynamic process which rises monotonically to a peak followed by a monotonic falling back. It was introduced to model the first stage of the Covid-19 pandemic to forecast its behaviour. Then, with different controls and variants, Covid-19 - rose and fell in what might be called a Multi-Wave (MW) behaviour;with waves not necessarily the same size. This paper shows how using the SL function for one wave can be easily modified to model the MW situation. We apply it to two examples. One is to Covid-19, to examine its most recent behaviour. We also apply it to climate change, the most serious issue of our time. Ensuring that the world simply achieves carbon-equality is not enough. We have to rapidly achieve carbon-negativity to prevent bringing an end to the known world. © SW 2023.All rights reserved

A review of some Covid-19 pandemic numbers in European Union, Canada, and Mexico

The rapidity and extent of Covid-19 infections have shown how a phenomenon that initially seemed geographically circumscribed quickly spread worldwide. In 2020, the spread of infection and the containment and management measures taken by local governments have been quite heterogeneous. Therefore, here we investigate the different ways of the spread of the infection in different areas, and specifically in Canada, Mexico, and the European Union states. For this purpose, for each area, official data on infection in 2020 are used to depict, analyze, and compare the monthly contagion's curves and the Rt index, both in absolute and relative terms. © Springer Nature Switzerland AG 2023. All rights reserved.

Threshold conditions for curbing COVID-19 with a dynamic zero-case policy derived from 101 outbreaks in China.

By 31 May 2022, original/Alpha, Delta and Omicron strains induced 101 outbreaks of COVID-19 in mainland China. Most outbreaks were cleared by combining non-pharmaceutical interventions (NPIs) with vaccines, but continuous virus variations challenged the dynamic zero-case policy (DZCP), posing questions of what are the prerequisites and threshold levels for success? And what are the independent effects of vaccination in each outbreak? Using a modified classic infectious disease dynamic model and an iterative relationship for new infections per day, the effectiveness of vaccines and NPIs was deduced, from which the independent effectiveness of vaccines was derived. There was a negative correlation between vaccination coverage rates and virus transmission. For the Delta strain, a 61.8% increase in the vaccination rate (VR) reduced the control reproduction number (CRN) by about 27%. For the Omicron strain, a 20.43% increase in VR, including booster shots, reduced the CRN by 42.16%. The implementation speed of NPIs against the original/Alpha strain was faster than the virus's transmission speed, and vaccines significantly accelerated the DZCP against the Delta strain. The CRN ([Formula: see text]) during the exponential growth phase and the peak time and intensity of NPIs were key factors affecting a comprehensive theoretical threshold condition for DZCP success, illustrated by contour diagrams for the CRN under different conditions. The DZCP maintained the [Formula: see text] of 101 outbreaks below the safe threshold level, but the strength of NPIs was close to saturation especially for Omicron, and there was little room for improvement. Only by curbing the rise in the early stage and shortening the exponential growth period could clearing be achieved quickly. Strengthening China's vaccine immune barrier can improve China's ability to prevent and control epidemics and provide greater scope for the selection and adjustment of NPIs. Otherwise, there will be rapid rises in infection rates and an extremely high peak and huge pressure on the healthcare system, and a potential increase in excess mortality.

Pulmonary Rehabilitation Outcomes of Post-Acute COVID-19 Patients during Different Waves of the Pandemic.

(1) Background: Between the beginning of the coronavirus pandemic and summer 2022, we distinguished four pandemic waves, with different characteristics of the affected patients. This study investigated the impact of patient characteristics on the outcome of inpatient pulmonary rehabilitation (PR). (2) Methods: Using a prospective approach, the characteristics of post-acute COVID-19 patients of the different waves who participated in inpatient PR were compared based on their assessments and results collected as part of PR (Cumulative Illness Rating Scale (CIRS), six-minute walk test (6-MWT), Pulmonary Function Testing (PFT), and Functional Independent Measurement (FIM). (3) Results: A total of 483 patients were included in the analysis (Wave 1 n = 51, Wave 2 n = 202, Wave 3 n = 84, Wave 4 n = 146). Compared to Wave 3 + 4, patients of Wave 1 + 2 were older (69 vs. 63 years; p < 0.001), had a significantly lower CIRS (13.0 vs. 14.7 points; p = 0.004), had significant better PFT (FVC: 73 vs. 68%pred; p = 0.009; DLCOSB: 58 ± 18 vs. 50 ± 17%pred; p = 0.001), and showed significantly more comorbidities (2.0 vs. 1.6 n/pers.; p = 0.009). Wave 3 + 4 showed significantly greater improvements according to the 6-MWT (147 vs. 188 m; p < 0.001) and the FIM (5.6 vs. 21.1 points; p < 0.001). (4) Conclusions: Patients of the COVID-19 infection waves differed significantly according to their anthropometric data, incidence of comorbidities, and impact of the infection. All cohorts achieved clinically relevant and significant functional improvements during PR, with significant higher improvements in Wave 3 + 4.

Unchanged Characteristics and Survival among Critically Ill COVID-19 Patients during First, Second, and Third Waves: A Prospective Observational Cohort.

BACKGROUND: This study was carried out to compare characteristics and outcomes in patients with acute respiratory failure related to COVID-19 during first, second, and third waves. METHODS: We included consecutive adults admitted to the intensive care unit between March 2020 and July 2021. We compared three groups defined by the epidemic intake phase: waves 1 (W1), 2 (W2), and 3 (W3). RESULTS: We included 289 patients. Two hundred and eight (72%) patients were men with a median age of 63 years (IQR: 54-72), of whom 68 (23.6%) died in hospital. High-flow nasal oxygen (HFNO) was inversely associated with the need for invasive mechanical ventilation (MV) in multivariate analysis (p = 0.003) but not dexamethasone (p = 0.25). The day-90 mortality rate did not vary from W1 (27.4%) to W2 (23.9%) and W3 (22%), p = 0.67. By multivariate analysis, older age (odds ratio [OR]: 0.94/year, p < 0.001), immunodeficiency (OR: 0.33, p = 0.04), acute kidney injury (OR: 0.26, p < 0.001), and invasive MV (OR: 0.13, p < 0.001) were inversely associated with higher day-90 survival as opposed to the use of intermediate heparin thromboprophylaxis dose (OR: 3.21, p = 0.006). HFNO use and dexamethasone were not associated with higher day-90 survival (p = 0.24 and p = 0.56, respectively). CONCLUSIONS: In patients with acute respiratory failure due to COVID-19, survival did not change between first, second, and third waves while the use of invasive MV decreased. HFNO or intravenous steroids were not associated with better outcomes, whereas the use of intermediate dose of heparin for thromboprophylaxis was associated with higher day-90 survival. Larger multicentric studies are needed to confirm our findings.

Genomic surveillance of severe acute respiratory syndrome coronavirus 2 in Burundi, from May 2021 to January 2022.

BACKGROUND: The emergence and rapid spread of new severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) variants have challenged the control of the COVID-19 pandemic globally. Burundi was not spared by that pandemic, but the genetic diversity, evolution, and epidemiology of those variants in the country remained poorly understood. The present study sought to investigate the role of different SARS-COV-2 variants in the successive COVID-19 waves experienced in Burundi and the impact of their evolution on the course of that pandemic. We conducted a cross-sectional descriptive study using positive SARS-COV-2 samples for genomic sequencing. Subsequently, we performed statistical and bioinformatics analyses of the genome sequences in light of available metadata. RESULTS: In total, we documented 27 PANGO lineages of which BA.1, B.1.617.2, AY.46, AY.122, and BA.1.1, all VOCs, accounted for 83.15% of all the genomes isolated in Burundi from May 2021 to January 2022. Delta (B.1.617.2) and its descendants predominated the peak observed in July-October 2021. It replaced the previously predominant B.1.351 lineage. It was itself subsequently replaced by Omicron (B.1.1.529, BA.1, and BA.1.1). Furthermore, we identified amino acid mutations including E484K, D614G, and L452R known to increase infectivity and immune escape in the spike proteins of Delta and Omicron variants isolated in Burundi. The SARS-COV-2 genomes from imported and community-detected cases were genetically closely related. CONCLUSION: The global emergence of SARS-COV-2 VOCs and their subsequent introductions in Burundi was accompanied by new peaks (waves) of COVID-19. The relaxation of travel restrictions and the mutations occurring in the virus genome played an important role in the introduction and the spread of new SARS-COV-2 variants in the country. It is of utmost importance to strengthen the genomic surveillance of SARS-COV-2, enhance the protection by increasing the SARS-COV-2 vaccine coverage, and adjust the public health and social measures ahead of the emergence or introduction of new SARS-COV-2 VOCs in the country.

Efficacy of low-intensity pulsed ultrasound for the treatment of viral pneumonia: study protocol for a randomized controlled trial.

BACKGROUND: Viral pneumonia has always been a problem faced by clinicians because of its insidious onset, strong infectivity, and lack of effective drugs. Patients with advanced age or underlying diseases may experience more severe symptoms and are prone to severe ventilation dysfunction. Reducing pulmonary inflammation and improving clinical symptoms is the focus of current treatment. Low-intensity pulsed ultrasound (LIPUS) can mitigate inflammation and inhibit edema formation. We aimed to investigate the efficacy of therapeutic LIPUS in improving lung inflammation in hospitalized patients with viral pneumonia. METHODS: Sixty eligible participants with clinically confirmed viral pneumonia will be assigned to either (1) intervention group (LIPUS stimulus), (2) control group (null stimulus), or (3) self-control group (LIPUS stimulated areas versus non-stimulated areas). The primary outcome will be the difference in the extent of absorption and dissipation of lung inflammation on computed tomography. Secondary outcomes include changes in lung inflammation on ultrasonography images, pulmonary function, blood gas analysis, fingertip arterial oxygen saturation, serum inflammatory factor levels, the sputum excretion volume, time to the disappearance of pulmonary rales, pneumonia status score, and course of pneumonia. Adverse events will be recorded. DISCUSSION: This study is the first clinical study of the efficacy of therapeutic LIPUS in the treatment of viral pneumonia. Given that the current clinical recovery mainly depends on the body's self-limiting and conventional symptomatic treatment, LIPUS, as a new therapy method, might be a major advance in the treatment of viral pneumonia. TRIAL REGISTRATION: ChiCTR2200059550 Chinese Clinical Trial Registry, May 3, 2022.

Multisystem inflammatory syndrome in children during the COVID-19 waves: data from the Juvenile Inflammatory Rheumatism cohort.

Introduction: Multisystem inflammatory syndrome in children (MIS-C) is a new condition that first appeared in children and adolescents during the COVID-19 pandemic. We aimed to describe the diagnostic course, clinical and biological manifestations, and treatment of MIS-C during the first three COVID-19 waves. Methods: We extracted patient data from the Juvenile Inflammatory Rheumatism (JIR) cohort. We analyzed data for patients meeting the World Health Organization diagnostic criteria for MIS-C from the start of the COVID-19 pandemic from March 2020 to June 30, 2021. We then compared data for patients in wave one to those in waves two and three. Results: We identified 136 patients with MIS-C. The median age decreased but not significantly during the waves, from 9.9 years to 7.3 years (p = 0.105). Boys represented 52.2% (n = 71) of patients, and 46% (n = 41) of patients originated from sub-Saharan Africa (p < 0.001). Patients presented less diarrhea (p = 0.004), respiratory distress (p < 0.001), and myocarditis (p < 0.001) with progressive waves. Biological inflammation also decreased, namely, C-reactive protein level (p < 0.001), neutrophil count (p = 0.004), and albumin level (p < 0.001). Patients received more corticosteroids (p < 0.001) and required less ventilation support (p < 0.01) and less inotrope treatment (p < 0.001) in the later waves. The duration of hospitalization gradually decreased (p < 0.001), as did critical care unit admissions (p = 0.002). Conclusion: Over the three COVID-19 waves, with a change in the management of MIS-C, children in the JIR cohort in France showed a less severe disease course, in particular, a greater use of corticosteroids. This observation may reflect the impact of both improved management and different SARS-CoV-2 variant.

Probing environmental and tectonic changes underneath Mexico City with the urban seismic field

The sediments underneath Mexico City have unique mechanical properties that give rise to strong site effects. We investigated temporal changes in the seismic velocity at strong-motion and broadband seismic stations throughout Mexico City, including sites with different geologic characteristics ranging from city center locations situated on lacustrine clay to hillside locations on volcanic bedrock. We used autocorrelations of urban seismic noise, enhanced by waveform clustering, to extract subtle seismic velocity changes by coda wave interferometry. We observed and modeled seasonal, co- and post-seismic changes, as well as a long-term linear trend in seismic velocity. Seasonal variations can be explained by self-consistent models of thermoelastic and poroelastic changes in the subsurface shear wave velocity. Overall, sites on lacustrine clay-rich sediments appear to be more sensitive to seasonal surface temperature changes, whereas sites on alluvial and volcaniclastic sediments and on bedrock are sensitive to precipitation. The 2017 Mw 7.1 Puebla and 2020 Mw 7.4 Oaxaca earthquakes both caused a clear drop in seismic velocity, followed by a time-logarithmic recovery that may still be ongoing for the 2017 event at several sites or that may remain incomplete. The slope of the linear trend in seismic velocity is correlated with the downward vertical displacement of the ground measured by interferometric synthetic aperture radar, suggesting a causative relationship and supporting earlier studies on changes in the resonance frequency of sites in the Mexico City basin due to groundwater extraction. Our findings show how sensitively shallow seismic velocity and, in consequence, site effects react to environmental, tectonic and anthropogenic processes. They also demonstrate that urban strong-motion stations provide useful data for coda wave monitoring given sufficiently high-amplitude urban seismic noise.

Description of the clinical picture of COVID-19 in patients with fatal outcome

In the Chelyabinsk region in 2020, 33 473 cases of a new coronavirus infection (COVID-19) were detected, of which 493 were fatal. The peak incidence of COVID-19 was recorded in November-December 2020. Purpose of research: description of the course of the infectious process of COVID-19 in patients with a fatal outcome. Material and methods. A retrospective analysis of case histories of patients with COVID-19 who had a lethal outcome was carried out using the method of continuous sampling from November 2020 to April 2021 on the basis of the Regional Infectious Diseases Center of the Regional Clinical Hospital No. 3 of the Chelyabinsk Region. Diagnosis was based on a comprehensive assessment of the anamnesis, clinical, laboratory and instrumental data in accordance with the Interim Guidelines "Prevention, Diagnosis and Treatment of Novel Coronavirus Infection (COVID-19)" version 9 dated 10/26/2020. Verification of the etiological diagnosis was carried out by PCR with reverse transcription to detect SARS-CoV-2 RNA in the nasopharyngeal secretion. The autopsy material was studied in the Pathoanatomical Department No. 9 of the Chelyabinsk Regional Pathological Bureau. Results and discussion. The average age of patients with a fatal outcome was 70 years, more often they were people with blood groups I and II, not vaccinated against COVID-19, pneumococcal infection and influenza;no gender differences were found. For patients with a fatal outcome from COVID-19, the presence of concomitant pathology is most characteristic: arterial hypertension (58%), atherosclerosis (45%), type 2 diabetes mellitus (41.5%), malignant neoplasms (17%). Among the "lethal patients", 50% had lung lesions at admission CT 2 and 25% had changes in the lungs consistent with CT 1;there was also a violation of cognitive functions in 21% of individuals. When comparing the analysis of studies of autopsy material and the clinical picture of patients, it was found that the morphological substrate of COVID-19 is both diffuse alveolar damage and simultaneous damage to the vascular bed, which is accompanied by damage to various organs and systems of the patient's body.Copyright © Eco-Vector, 2022.

COVID-19 Waves and Politics in Costa Rica

In 2018, the government that came to power in Costa Rica quickly began to promote socially regressive policies, which directly favored the oligarchic groups, at the expense of the working classes and the middle sectors. The COVID-19 pandemic, instead of stopping this process, accentuated it. After a very moderate first wave of infections (March-May 2020), the disease spread steadily during a second wave (June 2020-February 2021). A third wave (so far May-June 2021) has brought the public health system to the brink of collapse. With the social protests neutralized by health measures to contain COVID-19, authorities took advantage of this situation to promote new reforms that deteriorate labor rights, reduce wages and deepen inequalities. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2022.

Three years of COVID-19 and life satisfaction in Europe: A macro view.

Every country in Europe experienced an adverse impact from the COVID-19 pandemic on life satisfaction, though on average, satisfaction with life in the summer of 2022 is about the same as the pre-pandemic value in the autumn of 2019. Typically, an upsurge in the severity of the pandemic (measured by the number of COVID-related deaths) is associated with declining life satisfaction and an ebbing, with increasing life satisfaction. Of the three waves of the pandemic between March 2020 and the autumn of 2022, the most severe impact typically occurred in 2021 during the second wave; in the third wave, the response declined due to the spread of effective vaccines and the takeover of omicron variants.

Comparative Study of the Myocardium of Patients from Four COVID-19 Waves.

BACKGROUND: Few studies have compared COVID-19 patients from different waves. This study aims to conduct a clinical and morphological analysis of patients who died from COVID-19 during four waves. METHODS: The study involved 276 patients who died from COVID-19 during four waves, including 77 patients in the first wave, 119 patients in the second wave, and 78 patients in the third wave. We performed a histological examination of myocardium samples from autopsies and additionally analyzed the samples by PCR. We conducted immunohistochemistry of the myocardium for 21 samples using antibodies against CD3, CD45, CD8, CD68, CD34, Ang1, VWF, VEGF, HLA-DR, MHC1, C1q, enteroviral VP1, and SARS-CoV-2 spike protein. We also did immunofluorescent staining of three myocardial specimens using VP1/SARS-CoV-2 antibody cocktails. Further, we ran RT-ddPCR analysis for 14 RNA samples extracted from paraffin-embedded myocardium. Electron microscopic studies of the myocardium were also performed for two samples from the fourth wave. RESULTS: Among the 276 cases, active myocarditis was diagnosed in 5% (15/276). Of these cases, 86% of samples expressed VP1, and individual cells contained SARS-CoV-2 spike protein in 22%. Immunofluorescence confirmed the co-localization of VP1 and SARS-CoV-2 spike proteins. ddPCR did not confidently detect SARS-CoV-2 RNA in the myocardium in any myocarditis cases. However, the myocardium sample from wave IV detected a sub-threshold signal of SARS-CoV-2 by qPCR, but myocarditis in this patient was not confirmed. Electron microscopy showed several single particles similar to SARS-CoV-2 virions on the surface of the endothelium of myocardial vessels. A comparison of the cardiovascular complication incidence between three waves revealed that the incidence of hemorrhage (48 vs. 24 vs. 17%), myocardial necrosis (18 vs. 11 vs. 4%), blood clots in the intramural arteries (12 vs. 7 vs. 0%), and myocarditis (19 vs. 1 vs. 6%) decreased over time, and CD8-T-killers appeared. Immunohistochemistry confirmed the presence of endotheliitis in all 21 studied cases. CONCLUSIONS: This study compared myocardial damage in patients who died during three COVID-19 waves and showed a decrease in the incidence of endotheliitis complications (thrombosis, hemorrhage, necrosis) and myocarditis over time. However, the connection between myocarditis and SARS-CoV-2 infection remains unproven.

Comparative Study Between the First and Second Wave of COVID-19 Deaths in India: A Single Center Study.

Introduction  The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is continuously evolving, and many mutant variants of the virus are circulating in the world. Recurrent waves of COVID-19 have caused enormous mortality all across the globe. Considering the novelty of the virus, it becomes crucial for healthcare experts and policymakers to understand the demographic and clinical attributes of inpatient deaths in the first and second waves of COVID-19. Methods This hospital record-based comparative study was conducted at a tertiary care hospital in Uttarakhand, India. The study included all COVID-19 RT PCR-positive patients admitted to the hospital during the first wave, from 1st April 2020 to 31st January 2021, and the second wave from 1st March 2021 to 30th June 2021. Comparisons were made with respect to demographic, clinical, laboratory parameters, and course of hospital stay. Results The study exhibited 11.34% more casualties in the second wave, with the number of deaths being 424 and 475 for the first and second waves, respectively. A male preponderance of mortality was evident in both waves with significant differences (p=0.004). There was no significant difference in age between the two waves (p=0.809). The significantly different comorbidities were hypertension (p=0.003) and coronary artery disease (p=0.014). The clinical manifestations demonstrating a significant difference were cough (p=0.000), sore throat (p=0.002), altered mental status (p=0.002), headache (p=0.025), loss of taste and smell (p=0.001), and tachypnea (p=0.000). The lab parameters with a significant difference across both waves were lymphopenia (p=0.000), elevated aspartate aminotransferase (p=0.004), leukocytosis (p=0.008), and thrombocytopenia (p=0.004). During the hospital course of the second wave, in terms of intensive care unit stay, the need for non-invasive ventilation and inotrope support was higher. The complications manifesting in the form of acute respiratory distress syndrome and sepsis were observed more in the second wave. A significant difference was discerned in the median duration of hospital stay in both waves (p=0.000). Conclusion Despite being of shorter duration, the second wave of COVID-19 culminated in more deaths. The study demonstrated that most of the baseline demographic and clinical characteristics attributed to mortality were more common during the second wave of COVID-19, including lab parameters, complications, and duration of hospital stays. The unpredictable nature of COVID-19 waves calls for instituting a well-planned surveillance mechanism in place to identify the surge in cases at the earliest possible time and prompt response, along with developing infrastructure and capacity to manage complications.

Individual risk-aversion responses tune epidemics to critical transmissibility (R = 1).

Changes in human behaviour are a major determinant of epidemic dynamics. Collective activity can be modified through imposed control measures, but spontaneous changes can also arise as a result of uncoordinated individual responses to the perceived risk of contagion. Here, we introduce a stochastic epidemic model implementing population responses driven by individual time-varying risk aversion. The model reveals an emergent mechanism for the generation of multiple infection waves of decreasing amplitude that progressively tune the effective reproduction number to its critical value R = 1. In successive waves, individuals with gradually lower risk propensity are infected. The overall mechanism shapes well-defined risk-aversion profiles over the whole population as the epidemic progresses. We conclude that uncoordinated changes in human behaviour can by themselves explain major qualitative and quantitative features of the epidemic process, like the emergence of multiple waves and the tendency to remain around R = 1 observed worldwide after the first few waves of COVID-19.

The Waves and Cycles of COVID-19 Pandemic: A Phase Synchronization Approach

This study pretends to contribute to a better understanding of the COVID-19 dynamics through the non-parametric technique of phase synchronization by comparing the fifteen most affected countries by the number of positive cases plus China, where the first outbreak took place in December 2019. It was possible to state the number of cycles and waves for each one of the studied countries and to determine periods of synchronization between them. The results also showed the average duration of the cycles and some coincidences regarding Nason (2020);Bontempi (2021);Coccia (2021);Rusinol, Zammit, Itarte, Fores, Martinez-Puchol, Girones, Borrego, Corominas, and Bofill-Mas (2021). This study is limited by the reliability of the number of positive cases reported by national governments and health authorities because of an insufficient number of tests and a great number of asymptomatic persons but presents a legit alternative to predict the evolution of the pandemic in a country due to the forward looking behavior of another one, therefore studies like this could be useful to implement contention measures and to prepare the health systems in advance.