Relationship between neurological manifestations and severity of COVID-19. San Vicente de Paul Hospital. Ecuador 2021.

Introduction: SARS-CoV-2 mainly affects the respiratory system, but the damage caused by this virus also extends to other systems, including the nervous system, and the mechanisms of neurological infection can be direct or indirect. Objective(s): To determine the relationship between neurological manifestations and disease severity in symptomatic COVID-19 positive patients at San Vicente de Paul Hospital in 2021. Material(s) and Method(s): A cross-sectional observational study was conducted using medical records of patients hospitalized with COVID-19 and neurological manifestations, which were classified into manifestations of the central nervous system and manifestations of the peripheral nervous system. Result(s): The results show that 74,1 % of patients presented neurological manifestations;the highest percentage was concentrated in patients who developed severe disease (15 [60 %], CNS;91 [77,1 %], PNS;125 [65,4 %], CNS and PNS). The joint presence of central and peripheral neurological manifestations was significantly associated with critical COVID-19 (P value= 0,011;OR: 2,005). The mortality rate reached 2,69 %. Conclusion(s): Neurological manifestations in hospitalized COVID-19 patients are very common, and critical COVID-19 is more likely to have neurological manifestations.Copyright © 2022 Universidad de Ciencias Medicas de La Hab. All rights reserved.

Modified SEIR epidemic model including asymptomatic and hospitalized cases with correct demographic evolution

The aim of this study is to propose a modified Susceptible-Exposed-Infectious-Removed (SEIR) model that describes the time behaviour of symptomatic, asymptomatic and hospitalized patients in an epidemic, taking into account the effect of the demographic evolution. Unlike most of the recent studies where a constant ratio of new individuals is considered, we consider a more correct assumption that the growth ratio is proportional to the total population, following a Logistic law, as is usual in population growth studies for humans and animals. An exhaustive theoretical study is carried out and the basic reproduction number R0 is computed from the model equations. It is proved that if R0<1 then the disease-free manifold is globally asymptotically stable, that is, the epidemics remits. Global and local stability of the equilibrium points is also studied. Numerical simulations are used to show the agreement between numerical results and theoretical properties. The model is fitted to experimental data corresponding to the pandemic evolution of COVID-19 in the Republic of Cuba, showing a proper behaviour of infected cases which let us think that can provide a correct estimation of asymptomatic cases. In conclusion, the model seems to be an adequate tool for the study and control of infectious diseases.

Heterogeneous influence of individuals' behavior on mask efficacy in gathering environments

Wearing masks is an easy way to operate and popular measure for preventing epidemics. Although masks can slow down the spread of viruses, their efficacy in gathering environments involving heterogeneous person-to-person contacts remains unknown. Therefore, we aim to investigate the epidemic prevention effect of masks in different real-life gathering environments. This study uses four real interpersonal contact datasets to construct four empirical networks to represent four gathering environments. The transmission of COVID-19 is simulated using the Monte Carlo simulation method. The heterogeneity of individuals can cause mask efficacy in a specific gathering environment to be different from the baseline efficacy in general society. Furthermore, the heterogeneity of gathering environments causes the epidemic prevention effect of masks to differ. Wearing masks can greatly reduce the probability of clustered epidemics and the infection scale in primary schools, high schools, and hospitals. However, the use of masks alone in primary schools and hospitals cannot control outbreaks. In high schools with social distancing between classes and in workplaces where the interpersonal contact is relatively sparse, masks can meet the need for prevention. Given the heterogeneity of individual behavior, if individuals who are more active in terms of interpersonal contact are prioritized for mask-wearing, the epidemic prevention effect of masks can be improved. Finally, asymptomatic infection has varying effects on the prevention effect of masks in different environments. The effect can be weakened or eliminated by increasing the usage rate of masks in high schools and workplaces. However, the effect on primary schools and hospitals cannot be weakened. This study contributes to the accurate evaluation of mask efficacy in various gathering environments to provide scientific guidance for epidemic prevention. © 2022, Higher Education Press.

Transmission of SARS-CoV2 and Strategies for Control of Infection: Lessons Learnt

Coronavirus has affected all spheres of human life;physical, mental, and social aspects to the limit which has never been experienced before. The major symptoms of COVID-19 infection are fever, cough, respiratory distress, loss of taste, loss of smell, body aches diarrhea, vomiting, and so on. Those having symptoms are tested for their COVID-19 infection status either by Rapid Antigen test or real-time polymerase chain reaction (RTPCR)/Gene Xpert method. Those found COVID-19 positive are shifted to COVID care centers or home isolation for 17 days. The epidemiological triad includes an agent (strains of SARS-CoV-2), host (immunocompromised person), environment (overcrowding, temperature, humidity, contaminated surfaces). Various strategies have been implemented from time to time to break the chain of transmission to contain the spread of infection. Various strategies at an individual level and the community level are implemented. Strategies such as wearing mask, frequent handwashing, maintaining a distance of minimum 2 m between two people, screening for risk factors, quarantine, isolation, surveillance, and contact tracing, defining high-risk areas into hotspots/containment zones or micro containment zones, issuing heating, ventilation, and air-conditioning guidelines, work from home and introduction of vaccine as prophylaxis for prevention against the infection were introduced by India as well as globally. The introduction of infection control measures has some good affects such as lowering air pollution level and controlling the unnecessary plight of the vehicle on roads but the people have faced some serious effects also such as, it pushed people more into poverty and more down in nutritional graph raising country rank in hunger index. Whatever the strategy be proposed it should be implemented keeping to view the pros and cons of each strategy. © The Author(s), under exclusive licence to Springer Nature Singapore Pte Ltd. 2021.

Nonlinear analysis and dynamics of COVID-19 mathematical model with optimal control strategies

Efficacy of the healthcare system and illumination (awareness) activities control COVID-19. To defend public health, the spreading pandemic of COVID-19 disease necessitates social distancing, wearing masks, personal cleanliness, and precautions. Due to inadequate awareness programs, COVID-19 rapidly increases in India. The primary goal of this research is to investigate the spreading behavior of the COVID-19 virus in India when people are aware of the disease. We find the optimum value of disease transmission rate and detection of the unidentified asymptomatic and symptomatic populations. An optimal control problem is designed with limited resource allocation to improve the recovered individuals. A stability analysis presents for emphasizes the relevance of disease awareness in preventing the spread of the disease. The control parameters are used to explore the increase and decrease of the infected individual with and without control in optimal control analysis. The model is simulated using the Hattaf-fractional derivative to study the memory effect in the epidemic. To adapt the model to the total number of reported COVID-19 cases in India, we collected data from March 20, 2021 to September 30, 2021. According to the simulation results, the pandemic would spread faster if awareness campaigns were improperly carried out.

Evaluation of Early Diagnosis of COVID-19 Algorithms

The coronavirus disease 2019 (COVID-19) has been stated as a global pandemic, and the BA.4 and BA.5 variants are anticipated to drive the next wave of COVID-19 infection. Early diagnosis of this infection reduces its viral excretion. In this paper, after a large study of existing algorithms for pre-symptomatic COVID-19 detection in the state-of-the-art, we discovered a notable flaw in most models related to the choice of the evaluation function, such that, all the tested algorithms perform worse (from the evaluation function perspective) than an algorithm that generates alarms randomly from a binomial distribution. Therefore, we propose a simple and less biased evaluation function to better compare the quality of different algorithms. Comprehensive experimental evaluations of the state-of-the-art algorithms over the real-world dataset published by Nature Medicine journal contains 84 COVID-19 patients and 2,000 healthy participants show the effectiveness and the relevance of our evaluation method. Moreover, the proposed framework is released as an open-source library. © 2022 IEEE.

Subarachnoid hemorrhages and aneurysms during the SARS-CoV2-pandemia at a tertiary medical center - Analysis of incidence and outcome.

Introduction: During the COVID-19-pandemic a significant decrease of up to 13% of all kinds of medical emergencies was reported. Similar trends were expected for aneurysmal subarachnoid hemorrhages (aSAH) and/or symptomatic aneurysms. Research question: To analyze a correlation of the SARS-CoV2-infection and the incidence of aSAH, and to assess the impact of the pandemic-lockdown on the incidence, the outcome and the course of patients suffering from aSAH and/or aneurysms. Material and methods: From March 16th, 2020 (first lockdown in Germany) to January 31st, 2021, all patients admitted to our hospital were screened by polymerase-chain-reaction (PCR) test for genetic material of SARS-CoV2. During this period, aSAH and symptomatic cerebral aneurysms were assessed and retrospectively compared to a historic longitudinal case-cohort. Results: Of 109.927 PCR-tests, 7.856 (7.15%) revealed a SARS-CoV2-infection. None of the patients mentioned above were tested positively. The number of aSAH and symptomatic aneurysms rose by 20.5% (39 vs. 47 cases) (p â€‹= â€‹0.93). Poor grade aSAH, as well as extensive bleeding-patterns were more often observed (p â€‹= â€‹0.63 and p â€‹= â€‹0.40, respectively), with more symptomatic vasospasms diagnosed (5 vs. 9 patients). Mortality rate increased by 8,4%. Discussion and conclusion: A correlation between SARS-CoV2-infection and the incidence of aSAH could not be established. Still, the overall number and the number of poor-grade aSAHs increased as well as symptomatic aneurysms during the pandemic. Therefore, we might conclude that dedicated neurovascular competence should be retained in designated centers to care for these patients even or especially in special situations affecting the global healthcare system.

COVID-19 in Morocco's region: Observational study of prevalence in symptomatic adults using the PANBIOS® rapid antigen test September 2021.

Background: Rapid antigen tests have emerged to deal with the COVID-19 pandemic. Rapid diagnosis of SARS-CoV-2 infection is essential to reduce the spread of the disease. The aim of this study was to estimate the prevalence of COVID-19 infection and test the sensitivity and specificity in Temara-Skhirat in symptomatic adults through PANBIOS® test. Methods: A prospective observational study was conducted in mid-September 2021. Two investigators conducted data collection from symptomatic adult patients. The diagnostic performance of the PANBIOS®, and the PCR was assessed to calculate sensitivity and the specificity. Results: Among 206 symptomatic participants, the mean age was 38 ± 12 years, and the majority were women (59%). In our population, 80% had benefited from the anti-COVID vaccine. The median duration of symptoms was 4 days; the most common symptoms were fatigue (62%), headache (52%), fever (48%), cough (34%), loss of smell (25%), loss of taste (24%), and sore throat (22%). Results revealed 23% of cases tested positive with PANBIOS® test versus 30% with the PCR test. The calculated medical decision between PCR versus PANBIOS® test showed high specificity of 95.7% and a sensitivity of 69.4%. There was concordance between the PANBIOS® test and the PCR. Conclusion: The prevalence tested remain high, and the sensitivity and specificity of the PANBIOS® versus PCR test are similar to other literatures and close to value described in WHO recommendations. PANBIOS® is a useful test for controlling the spread of COVID-19 allowing identification of active infection.

Identification of psychoeducation needs and an intervention response for pre-symptomatic Huntington's disease.

People who are aware that they are gene-positive for Huntington's disease (HD) may face an array of personal, relationship, social, financial and employment challenges prior to the onset of the disease. These challenges have been associated with increased psychological problems such as anxiety and depression. Information and support for people with pre-symptomatic HD is indicated, but there is a scarcity of research and service models to inform psychological interventions. We trialled an intervention strategy involving psychoeducation forums designed specifically for pre-symptomatic HD. In phase I of the study, we asked people with pre-symptomatic HD to identify their uppermost needs for information. Phase II involved the delivery of this information via a series of forums. The forums also provided an opportunity for interaction among the participants. Three forums were attended by 88 people with pre-symptomatic HD and significant others. Analysis of post-forum feedback questionnaires indicated high levels of satisfaction with the forums' structure, content and relevance, and notably, the pre-symptomatic specificity of focus. Additional qualitative data from recordings of forum discussion groups revealed that participants greatly valued the opportunity to meet similar others, and share their concerns and strategies for addressing these concerns. There was an abundance of requests for more forums on a wide range of relevant topics. It is recommended that this model of intervention may be of value for implementation in other HD services or community groups.

Sensitivity of RT-PCR tests for SARS-CoV-2 through time.

Reverse transcriptase polymerase chain reaction (RT-PCR) tests are the gold standard for detecting recent infection with SARS-CoV-2. RT-PCR sensitivity varies over the course of an individual's infection, related to changes in viral load. Differences in testing methods, and individual-level variables such as age, may also affect sensitivity. Using data from New Zealand, we estimate the time-varying sensitivity of SARS-CoV-2 RT-PCR under varying temporal, biological and demographic factors. Sensitivity peaks 4-5 days post-infection at 92.7% [91.4%, 94.0%] and remains over 88% between 5 and 14 days post-infection. After the peak, sensitivity declined more rapidly in vaccinated cases compared to unvaccinated, females compared to males, those aged under 40 compared to over 40 s, and Pacific peoples compared to other ethnicities. RT-PCR remains a sensitive technique and has been an effective tool in New Zealand's border and post-border measures to control COVID-19. Our results inform model parameters and decisions concerning routine testing frequency.

Clinical profile of COVID 19 infection in children admitted in a dedicated COVID 19 treatment centre in South India

Background: COVID19 pandemic had affected millions of people worldwide. In contrast with adults, children had milder disease though transmission rate was high. During second wave of COVID 19, more children were affected Aim: To describe and compare the clinical profile of COVID 19 infection in children between the first and second waves. Methods: This was a descriptive cross-sectional study done by retrospective chart analysis. The study population included children from age group 1 month to 12 years admitted with a diagnosis of COVID 19 infection at a tertiary care centre in Kerala. Results: A total of 322 case records were analyzed and 52 were excluded due to incomplete data. Of the 270 records of children, 51(18.9%) were in 1st wave and 219 (81.1%) were in 2nd wave. Among the major clinical symptoms, fever and respiratory complaints were more common. There was significant difference in the mean age of children in 2 waves (2.47 years in 1st wave and 3.70 in second wave, P value 0.023). The proportion of asymptomatic patients were significantly higher during the 1st wave 39 (77%) compared to 2nd wave 98 (45%) with a significant p value of <0.001. Subgroup analysis was done for the presenting symptoms in which gastrointestinal and respiratory symptoms were predominant in the 2nd wave. There was no child mortality during both waves. Conclusion: The study showed significant difference in the presenting symptoms during the 1st and 2nd waves of COVID19 pandemic with higher rate of respiratory and gastrointestinal symptoms during the 2nd wave and more asymptomatic cases during the 1st wave. Since the symptomatology of presentation was evolving, the suspicion of COVID 19 as causative agent for respiratory and gastrointestinal symptoms should remain high. [ FROM AUTHOR] Copyright of Journal of Cardiovascular Disease Research (Journal of Cardiovascular Disease Research) is the property of Journal of Cardiovascular Disease Research and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full . (Copyright applies to all s.)

Glial fibrillary acidic protein astrocytopathy in a patient with recent mRNA SARS-CoV-2 vaccination: COVERSHEET

Background: Literature describing triggers of GFAP astrocytopathy (GFAP-A) is limited. We report a case of GFAP-A in a patient with recent messenger ribonucleic acid (mRNA) severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) vaccination and discuss the possible pathogenesis. Case description: A 45-year-old gentleman presented with features of meningoencephalitis 31 days after the first dose and 4 days after the second dose of mRNA SARS-CoV-2 vaccination. He sequentially developed brainstem/cerebellar, autonomic and cord dysfunction. Cerebrospinal fluid was positive for GFAP autoantibody. Clinical improvement occurred after intravenous methylprednisolone and immunoglobulins. Conclusion(s): Although we are uncertain of a causal link of GFAP-A to mRNA vaccine, indirect activation of an underlying dysregulated immune milieu is plausible.Copyright © 2021 The Author(s)

Narcolepsy due to a medical condition

"Narcolepsy due to a medical condition” (symptomatic or secondary narcolepsy) results from a specific underlying medical or neurological condition. Common causes are inherited disorders, tumors, head trauma, demyelinating diseases and stroke. Similar to idiopathic narcolepsy, aberrant T cell mediated cytotoxicity to host antigens in hypocretin neurons might be the underlying pathophysiology. Secondary narcolepsy cases have varying ages of onset, typically following a specific underlying medical or neurological disorder. Primary sleep disorders, mental disorders, or drug/substance use needs to be ruled out. Although the main treatment should be controlling underlying pathologic processes, use of wake promoting medications are often warranted. © 2023 Elsevier Inc. All rights reserved

Post COVID-19 syndrome and new onset diseases: A prospective observational study.

Introduction: The National Institute of Health and Care Excellence (NICE) has defined the terms, 'acute coronavirus disease 2019' (COVID-19), 'ongoing symptomatic COVID-19' and 'post-COVID-19 syndrome', with the latter two described as having persistent symptoms after the onset of COVID-19 symptoms for 4-12 weeks and >12 weeks, respectively. Persistent symptoms can either be due to the after-effects of COVID-19 or new-onset diseases after acute COVID-19. All symptoms observed beyond 4 weeks after the onset of COVID-19 need not be present at the time of onset. Previous studies on persistent post-COVID-19 symptoms have not mentioned new-onset diseases after acute COVID-19, and only a select few studies have discussed such new-onset symptoms. Methods: Ninety-five patients who attended the post-COVID-19 clinic completed the requisite follow-up till 16 weeks after COVID-19 symptom onset. Data was recorded on a predesigned proforma. Necessary investigations were conducted to rule out any other cause of persistent symptoms. Results: Fatigue (62.1%), breathlessness (50.5%) and cough (27.4%) were the most common symptoms present beyond 4 weeks after the onset of COVID-19 symptoms. Forty-nine (51.57%) patients developed post-COVID-19 syndrome - their severity of symptoms (odds ratio [OR] 17.77) and longer duration of hospital stay (OR 1.095) during acute disease were significantly associated with the development of post-COVID-19 syndrome. During follow-up, 25 patients developed new-onset symptoms, such as diabetes mellitus, hypertension and idiopathic tachycardia. Conclusion: Patients can have persistent symptoms, new-onset symptoms and new-onset diseases after recovery from acute COVID-19.

The quantity and quality of anti-SARS-CoV-2 antibodies show contrariwise association with COVID-19 severity: lessons learned from IgG avidity.

Gaining more appreciation on the protective/damaging aspects of anti-SARS-CoV-2 immunity associated with disease severity is of great importance. This study aimed to evaluate the avidity of serum IgG antibodies against SARS-CoV-2 spike (S) and nucleocapsid (N) in hospitalized symptomatic COVID-19 patients and asymptomatic RT-PCR-confirmed SARS-CoV-2 carriers as well as to compare antibody avidities with respect to vaccination status, vaccination dose and reinfection status. Serum levels of anti-S and anti-N IgG were determined using specific ELISA kits. Antibody avidity was determined by urea dissociation assay and expressed as avidity index (AI) value. Despite higher IgG levels in the symptomatic group, AI values of both anti-S and anti-N IgG were significantly lower in this group compared to asymptomatic individuals. In both groups, anti-S AI values were elevated in one-dose and two-dose vaccinees versus unvaccinated subjects, although significant differences were only detected in the symptomatic group. However, anti-N avidity showed no significant difference between the vaccinated and unvaccinated subgroups. Almost all vaccinated patients of different subgroups (based on vaccine type) had higher anti-S IgG avidity, while the statistical significance was detected only between those receiving Sinopharm compared to the unvaccinated subgroup. Also, statistically significant differences in antibody AIs were only found between primarily infected individuals of the two groups. Our findings indicate a key role for anti-SARS-CoV-2 IgG avidity in protection from symptomatic COVID-19 and calls for the incorporation of antibody avidity measurement into the current diagnostic tests to predict effective immunity toward SARS-CoV-2 infection or even for prognostic purposes.

A Novel Approach to Obtain Vaccine Effectiveness Continuous Profiles. Example Case: COVID-19 in Elderly Mexicans.

Population-wide vaccination is the most promising long-term COVID-19 disease management strategy. However, the protection offered by the currently available COVID-19 vaccines wanes over time, requiring boosters to be periodically given, which represents an unattainable challenge, especially if it is necessary to apply several doses per year. Therefore, it is essential to design strategies that contribute to maximizing the control of the pandemic with the available vaccines. Achieving this objective requires knowing, as precisely and accurately as possible, the changes in vaccine effectiveness over time in each population group, considering the eventual dependence on age, sex, etc. Thus, the present work proposes a novel approach to calculating realistic effectiveness profiles against symptomatic disease. In addition, this strategy can be adapted to estimate realistic effectiveness profiles against hospitalizations or deaths. All such time-dependent profiles allow the design of improved vaccination schedules, where each dose can be administrated to the population groups so that the fulfillment of the containment objectives is maximized. As a practical example for this analysis, vaccination against COVID-19 in Mexico was considered. However, this methodology can be applied to other countries' data or to characterize future vaccines with time-dependent effectiveness values. Since this strategy uses aggregated observational data collected from massive databases, assumptions about the data validity and the course of the studied epidemic could eventually be necessary.

Long-COVID-19 in Asymptomatic, Non-Hospitalized, and Hospitalized Populations: A Cross-Sectional Study.

A substantial proportion of coronavirus disease 2019 (COVID-19) survivors continue to suffer from long-COVID-19 (LC) symptoms. Our study aimed to determine the risk factors for LC by using a patient population from Northern Cyprus. Subjects who were diagnosed with severe acute respiratory syndrome-2 (SARS-CoV-2) infection in our university hospital were invited and asked to fill in an online questionnaire. Data from 296 survivors who had recovered from COVID-19 infection at least 28 days prior the study was used in the statistical analysis. For determination of risk factors for "ongoing symptomatic COVID-19 (OSC)" and "Post-COVID-19 (PSC)" syndromes, the patient population was further divided into group 1 (Gr1) and group 2 (Gr2), that included survivors who were diagnosed with COVID-19 within 4-12 weeks and at least three months prior the study, respectively. The number of people with post-vaccination SARS-CoV-2 infection was 266 (89.9%). B.1.617.2 (Delta) (41.9%) was the most common SARS-CoV-2 variant responsible for the infections, followed by BA.1 (Omicron) (34.8%), B.1.1.7 (Alpha) (15.5%), and wild-type SARS-CoV-2 (7.8%). One-hundred-and-nineteen volunteers (40.2%) stated an increased frequency of COVID-19-related symptoms and experienced the symptoms in the week prior to the study. Of those, 81 (38.8%) and 38 (43.7%) were from Gr1 and Gr2 groups, respectively. Female gender, chronic illness, and symptomatic status at PCR testing were identified as risk factors for developing OSC syndrome, while only the latter showed a similar association with PSC symptoms. Our results also suggested that ongoing and persistent COVID-19-related symptoms are not influenced by the initial viral cycle threshold (Ct) values of the SARS-CoV-2, SARS-CoV-2 variant as well as vaccination status and type prior to COVID-19. Therefore, strategies other than vaccination are needed to combat the long-term effect of COVID-19, especially after symptomatic SARS-CoV-2 infection, and their possible economic burden on healthcare settings.

Forecasting the impact of epidemic outbreaks on the supply chain: modelling asymptomatic cases of the COVID-19 pandemic

An epidemic outbreak largely disrupts supply chains (SCs) worldwide through plummeting business confidence, especially when it becomes a pandemic;its unpredictable re-emergence and spreadability may lead to inappropriate decision-making, in turn causing severe economic shocks. In March 2020, the coronavirus disease 2019 (COVID-19) outbreak attained a pandemic level, and many millions of cases were confirmed globally. Many countries reported an increasing number of active cases and formulated long-term lockdown guidelines, which resulted in an unexpected disruption of SCs. A key challenge in this scenario is that the rising number of confirmed COVID-19 cases does not necessarily reflect the already infected or asymptomatic cases. It is thus critical to understand the impact of asymptomatic carriers on the SC, as they may be the key driver of the novel virus spread, disrupting long-term SCs. This paper generalised the susceptible-exposed-infected-recovered (S-E-I-R) approach to create a mathematical model for which the impact of a proposed asymptomatic situation on the SC is evaluated through the basic reproduction number (R0), considered the main driver of SC disruption and the equilibrium status of infection over time. This paper presents an action plan for reducing disruption in the SC based on the R0 of the model. Overall, the current study as validated through a case study suggests that the asymptomatic-situation-based model is more convenient for critically understanding as well as forecasting the outbreak's impact on SCs. This study also highlights different perspectives of SCs for managing such types of pandemics using modelling approaches.

How big of an impact do asymptomatic people have on the dynamics of an epidemic?

Asymptomatic carriers serve as a potential source of transmission of epidemic diseases. Exposed people who develop symptoms only get tested and remain isolated in their homes or sometimes in hospitals when needed. In contrast, the asymptomatic individuals go untested and spread the disease silently as they roam freely throughout their entire infectious lifetime. The work intends to explore the role of asymptomatic carriers in the transmission of epidemic diseases and investigate suitable optimal control strategies. We propose a SEIAQR compartmental model subdividing the total population into six different compartments. To illustrate the model's implication, we estimate the number of asymptomatic individuals using COVID-19 data during June 9–July 18, 2021 from Bangladesh. We then analyze the model to explore whether the epidemic subsides if the asymptomatic individuals are tested randomly and isolated. Finally, to gain a better understanding of the potential of this unidentified transmission route, we propose an optimal control model considering two different control strategies: personal protective measures and isolation of asymptomatic carriers through random testing. Our results show that simultaneous implementation of both control strategies can reduce the epidemic early. Most importantly, sustained effort in identifying and isolation of asymptotic individuals allows relaxation in personal protective measures. © 2023

Dynamics of disease characteristics and viral RNA decay in patients with asymptomatic and mild infections during the Omicron wave in Shanghai, China: A retrospective cohort study.

OBJECTIVES: Asymptomatic infections and mild diseases were more common during the Omicron outbreak in Shanghai, China in 2022. This study aimed to assess the characteristics and viral RNA decay between patients with asymptomatic and mild infections. METHODS: A total of 55,111 patients infected with SARS-CoV-2 who were quarantined in the National Exhibition & Convention Center (Shanghai) Fangcang shelter hospital within 3 days after diagnosis from April 9 to May 23, 2022 were enrolled. The kinetics of cycle threshold (Ct) values of reverse transcription-polymerase chain reaction were assessed. The influencing factors for disease progression and the risk factors for the viral RNA shedding time (VST) were investigated. RESULTS: On admission, 79.6% (43,852/55,111) of the cases were diagnosed with asymptomatic infections, and 20.4% were mild diseases. However, 78.0% of initially asymptomatic subjects developed mild diseases at the follow-up. The final proportion of asymptomatic infections was 17.5%. The median time of symptom onset, the duration of symptoms, and the VST were 2 days, 5 days, and 7 days, respectively. Female, age 19-40 years, underlying comorbidities with hypertension and diabetes, and vaccination were associated with higher risks of progressing to mildly symptomatic infections. In addition, mildly symptomatic infections were found to be associated with prolonged VST compared with asymptomatic infections. However, the kinetics of viral RNA decay and dynamics of Ct values were similar among asymptomatic subjects, patients with asymptomatic-to-mild infection, and patients with mild infection. CONCLUSION: A large proportion of initially diagnosed asymptomatic Omicron infections is in the presymptomatic stage. The Omicron infection has a much shorter incubation period and VST than previous variants. The infectivity of asymptomatic infections and mildly symptomatic infections with Omicron is similar.