Proportion Of Asymptomatic Cases Research Articles

Spectrum of COVID-19 cases in Arkhangelsk, Northwest Russia: Findings from a population-based study linking serosurvey, registry data, and self-reports of symptoms.

The spectrum of COVID-19 manifestations makes it challenging to estimate the exact proportion of people who had the infection in a population, with the proportion of asymptomatic cases likely being underestimated. We aimed to assess and describe the spectrum of COVID-19 cases in a sample of adult population aged 40-74 years in Arkhangelsk, Northwest Russia, a year after the start of the pandemic. A population-based survey conducted between February 24, 2021 and June 30, 2021 with an unvaccinated sample aged 40-74 years (N = 1089) combined a serological survey data, national COVID-19 case registry, and self-reported data on COVID-19 experience and symptoms. Based on the agreement between these sources, we classified the study participants as non-infected and previously infected (asymptomatic, non-hospitalized and hospitalized symptomatic) cases, and compared these groups regarding demographics, lifestyle and health characteristics. After a year of the pandemic in Arkhangelsk, 59.7% 95% confidence intervals (CI) (56.7; 62.6) of the surveyed population had had COVID-19. Among those who had been infected, symptomatic cases comprised 47.1% 95% CI (43.2; 51.0), with 8.6% 95% CI (6.6; 11.1) of them having been hospitalized. Of the asymptomatic cases, 96.2% were not captured by the healthcare system. Older age was positively associated, while smoking showed a negative association with symptomatic COVID-19. Individuals older than 65 years, and those with poor self-rated health were more likely to be hospitalized. More than half of the infected individuals were not captured by the healthcare-based registry, mainly those with asymptomatic infections. COVID-19 severity was positively associated with older age and poor self-rated health, and inversely associated with smoking. Combining different sources of surveillance data could reduce the number of unidentified asymptomatic cases and enhance surveillance for emerging infections.

Impact of vaccination and high-risk group awareness on the mpox epidemic in the United States, 2022–2023: a modelling study

The unprecedented global outbreak of mpox in 2022 posed a public health challenge. In addition to the mpox vaccine campaign in the United States (US), community organisations and public health agencies initiated educational efforts to promote sexual risk reduction. This modelling study estimated the impact of the two-dose vaccination campaign and sexual behaviour changes coincident with high-risk group awareness on the mpox epidemic in the US. We fitted a deterministic, risk-structured SEIARV model to the epidemic curve of reported mpox cases in the US between May 22, 2022 and December 22, 2022. We evaluated the putative effects of the two preventive responses in the US -- vaccination and sexual risk reduction -- at the population-level, by calculating the prevention percentages of cumulative cases compared to the counterfactual scenario without interventions. We performed sensitivity analyses with four parameters: case reporting fidelity, vaccine effectiveness, proportion of asymptomatic cases, and assortative mixing. Model fitting revealed a basic reproduction number of 3.88 and 0.39 for the high-risk and low-risk populations, respectively, with 71.8% of mpox cases estimated from the high-risk population. A two-dose vaccination campaign, solely, could prevent 21.2% (10.2%-24.1%) of cases, while behaviour changes due to high-risk group awareness alone could prevent 15.4% (14.3%-20.6%). The combination of both measures were synergistic, with the model suggesting that 64.0% (43.8%-69.0%) of US cases were averted that would have otherwise occurred. Our models suggest that the 2022-2023 mpox epidemic in the US was controlled by a combination of two-dose mpox vaccination campaign and high-risk group awareness and sexual risk reduction. Taiwan Ministry of Education grant #NTU-112L9004, Taiwan National Science and Technology Council grant #MOST-109-2314-B-002-147-MY3 and grant #NSC-112-2314-B-002-216-MY3. SHV was supported, in part, by US National Institutes of Health grant #P30MH062294.

A Case Control Study on Risk Factors and Drug Prescription Patterns in Glaucoma at a tertiary eye care center in a city of Western India

Introduction: Glaucoma is an idiopathic, progressive optic disc neuropathy complicating into irreversible blindness if untreated. Early diagnosis by screening cases from high-risk populations has a pivotal role in managing this major public health problem with high treatment expenditures. Objectives: To identify the various ocular and non ocular risk factors of glaucoma and to identify the drug prescription pattern among glaucoma patients. Method: This was an observational, case-control study including 165 adult Glaucoma patients on treatment as cases and 165 age and sex-matched healthy individuals as controls, all of which were randomly selected from the patients visiting a tertiary eye care center. Various risk factors, drug prescription pattern and symptoms of the patients were recorded and analyzed.Results: A total of 165 adult Glaucoma patients and age and gender matched 165 controls were enrolled. Majority of the patients (41.21%) complained of blurring of vision at the time of study. The Odds ratios for Family history, Hypertension, Diabetes Mellitus, Migraine, Sleep apnea and Smoking showed strong association as risk factors for Glaucoma and the differences between the two groups were statistically significant (p value < 0.05). The mean number of drugs per prescription ± SD was 1.88 ± 0.79. Fixed drug formulations were prescribed in 42.4% patients. All the drugs were prescribed by their brand names and majority of them were in the form of eye drops. Conclusion: Primary Open Angle Glaucoma (POAG) was the most common subtype in the study. Age, Family history, Myopia, Hypertension, Diabetes Mellitus, Sleep Apnea, Migraine, Corticosteroid usage and Smoking emerged as putative risk factors. In consistence with present guidelines, Prostaglandin analogs were the most prescribed antiglaucoma drugs. The considerable proportion of asymptomatic cases (23%) suggests the need for periodic eye examinations to detect glaucomatous changes at an early stage.

Asymptomatic COVID-19 Individuals Tend to Establish Relatively Balanced Innate and Adaptive Immune Responses.

The sharp increase in the proportion of asymptomatic cases and the potential risk of virus transmission have greatly increased the difficulty of controlling the COVID-19 pandemic. The individual immune response is closely associated with clinical outcomes and pathogenic mechanisms of COVID-19. However, the clinical characteristics and immunophenotyping features of immune cells of asymptomatic individuals remain somewhat mysterious. To better understand and predict the disease state and progress, we performed a comprehensive analysis of clinical data, laboratory indexes and immunophenotyping features in 41 patients with SARS-CoV-2 (including 24 asymptomatic cases and 17 symptomatic individuals). Firstly, from the perspective of demographic characteristics, the rate of asymptomatic infection was significantly higher in those with younger age. Secondly, the laboratory test results showed that some indexes, such as CRP (acute phase reaction protein), D-Dimer and fibrinogen (the marker for coagulation) were lower in the asymptomatic group. Finally, symptomatic individuals were prone to establishing a non-protective immune phenotype by abnormally decreasing the lymphocyte count and percentage, abnormally increasing the Th17 percentage and decreasing Treg percentage, which therefore cause an increase in the neutrophil/lymphocyte ratio (NLR), monocytes/lymphocytes ratio (MLR) and Th17/Treg ratio. On the other hand, asymptomatic individuals tended to establish a more effective and protective immune phenotype by maintaining a normal level of lymphocyte count and percentage and a high level of NK cells. At the same time, asymptomatic individuals can establish a relatively balanced immune response through maintaining a low level of monocytes, a relatively low level of Th17 and high level of Treg, which therefore lead to a decrease in MNKR and Th17/Treg ratio and finally the avoidance of excessive inflammatory responses. This may be one of the reasons for their asymptomatic states. This study is helpful to reveal the immunological characteristics of asymptomatic individuals, understand immune pathogenesis of COVID-19 and predict clinical outcomes more precisely. However, owing to small sample sizes, a future study with larger sample size is still warranted.

Clinical and epidemiological profile of Indian COVID-19 patients from Jaipur: a descriptive study

We analyzed the data of 102 confirmed patients with novel Coronavirus 2 infection (COVID-19) during the early period of nationwide lockdown announced in India after the declaration of pandemic. We analyzed epidemiological, clinical characteristics and outcome of hospitalization in 102 patients with positive results for novel corona virus (SARS-CoV-2) RNA testing which were traced on the basis of history of travel, contact with a confirmed COVID-19 case, resident of hotspot areas or presence of symptoms, thus providing an accurate estimate of the proportion of asymptomatic cases in the initial population. Of 102 patients enrolled in the study, 83.3% (85/102) were asymptomatic and 16.67% (17/102) were symptomatic. Seventy-seven (75.49%) were males and 24.50% (25/102) were females. Eighteen (17.6%) patients had associated comorbidities, the most prevalent of which were diabetes mellitus 10.8% (11/102), hypertension 7.8% (8/102), chronic obstructive pulmonary disease (COPD) in 3.92% (4/102), chronic kidney Disease (CKD) 0.98% (1/102), coronary artery Disease (CAD) 0.98% (1/102) and cerebro-vascular disease (CVD) 0.98% (1/102). The clinical spectrum among symptomatic COVID-19 patients varied from dry cough and fever to respiratory failure and multi-organ failure. Twelve (11.76%) patients were kept in intensive care unit (ICU). Ninety-nine (97.05%) patients recovered while three (2.94%) died during hospital stay. With majority of COVID-19 cases in India being asymptomatic, changes in biochemical and inflammatory profile were small and insignificant in asymptomatic patients when compared to symptomatic patients. Elevated NLR, lymphopenia, age and presence of comorbidities were associated with increased severity and poor outcome.

Estimating the Prevalence of Asymptomatic COVID-19 Cases and Their Contribution in Transmission - Using Henan Province, China, as an Example.

Background: Novel coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-COV-2), is now sweeping across the world. A substantial proportion of infections only lead to mild symptoms or are asymptomatic, but the proportion and infectivity of asymptomatic infections remains unknown. In this paper, we proposed a model to estimate the proportion and infectivity of asymptomatic cases, using COVID-19 in Henan Province, China, as an example.Methods: We extended the conventional susceptible-exposed-infectious-recovered model by including asymptomatic, unconfirmed symptomatic, and quarantined cases. Based on this model, we used daily reported COVID-19 cases from January 21 to February 26, 2020, in Henan Province to estimate the proportion and infectivity of asymptomatic cases, as well as the change of effective reproductive number, Rt.Results: The proportion of asymptomatic cases among COVID-19 infected individuals was 42% and the infectivity was 10% that of symptomatic ones. The basic reproductive number R0 = 2.73, and Rt dropped below 1 on January 31 under a series of measures.Conclusion: The spread of the COVID-19 epidemic was rapid in the early stage, with a large number of asymptomatic infected individuals having relatively low infectivity. However, it was quickly brought under control with national measures.

Quantifying SARS-CoV-2 Infection Risk Within the Google/Apple Exposure Notification Framework to Inform Quarantine Recommendations.

Most early Bluetooth‐based exposure notification apps use three binary classifications to recommend quarantine following SARS‐CoV‐2 exposure: a window of infectiousness in the transmitter, ≥15 minutes duration, and Bluetooth attenuation below a threshold. However, Bluetooth attenuation is not a reliable measure of distance, and infection risk is not a binary function of distance, nor duration, nor timing. We model uncertainty in the shape and orientation of an exhaled virus‐containing plume and in inhalation parameters, and measure uncertainty in distance as a function of Bluetooth attenuation. We calculate expected dose by combining this with estimated infectiousness based on timing relative to symptom onset. We calibrate an exponential dose–response curve based on infection probabilities of household contacts. The probability of current or future infectiousness, conditioned on how long postexposure an exposed individual has been symptom‐free, decreases during quarantine, with shape determined by incubation periods, proportion of asymptomatic cases, and asymptomatic shedding durations. It can be adjusted for negative test results using Bayes' theorem. We capture a 10‐fold range of risk using six infectiousness values, 11‐fold range using three Bluetooth attenuation bins, ∼sixfold range from exposure duration given the 30 minute duration cap imposed by the Google/Apple v1.1, and ∼11‐fold between the beginning and end of 14 day quarantine. Public health authorities can either set a threshold on initial infection risk to determine 14‐day quarantine onset, or on the conditional probability of current and future infectiousness conditions to determine both quarantine and duration.

Transmission dynamics and control of two epidemic waves of SARS-CoV-2 in South Korea

BackgroundAfter relaxing social distancing measures, South Korea experienced a resurgent second epidemic wave of coronavirus disease 2019 (COVID-19). In this study, we aimed to identify the transmission dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and assess the impact of COVID-19 case finding and contact tracing in each epidemic wave.MethodsWe collected data on COVID-19 cases published by local public health authorities in South Korea and divided the study into two epidemic periods (19 January–19 April 2020 for the first epidemic wave and 20 April–11 August 2020 for the second epidemic wave). To identify changes in the transmissibility of SARS-CoV-2, the daily effective reproductive number (Rt) was estimated using the illness onset of the cases. Furthermore, to identify the characteristics of each epidemic wave, frequencies of cluster types were measured, and age-specific transmission probability matrices and serial intervals were estimated. The proportion of asymptomatic cases and cases with unknown sources of infection were also estimated to assess the changes of infections identified as cases in each wave.ResultsIn early May 2020, within 2-weeks of a relaxation in strict social distancing measures, Rt increased rapidly from 0.2 to 1.8 within a week and was around 1 until early July 2020. In both epidemic waves, the most frequent cluster types were religious-related activities and transmissions among the same age were more common. Furthermore, children were rarely infectors or infectees, and the mean serial intervals were similar (~ 3 days) in both waves. The proportion of asymptomatic cases at presentation increased from 22% (in the first wave) to 27% (in the second wave), while the cases with unknown sources of infection were similar in both waves (22 and 25%, respectively).ConclusionsOur study shows that relaxing social distancing measures was associated with increased SARS-CoV-2 transmission despite rigorous case findings in South Korea. Along with social distancing measures, the enhanced contact tracing including asymptomatic cases could be an efficient approach to control further epidemic waves.

Mass Testing With Contact Tracing Compared to Test and Trace for the Effective Suppression of COVID-19 in the United Kingdom: Systematic Review.

BackgroundMaking testing available to everyone and tracing contacts might be the gold standard to control COVID-19. Many countries including the United Kingdom have relied on the symptom-based test and trace strategy in bringing the COVID-19 pandemic under control. The effectiveness of a test and trace strategy based on symptoms has been questionable and has failed to meet testing and tracing needs. This is further exacerbated by it not being delivered at the point of care, leading to rising cases and deaths. Increases in COVID-19 cases and deaths in the United Kingdom despite performing the highest number of tests in Europe suggest that symptom-based testing and contact tracing might not be effective as a control strategy. An alternative strategy is making testing available to all.ObjectiveThe primary objective of this review was to compare mass testing and contact tracing with the conventional test and trace method in the suppression of SARS-CoV-2 infections. The secondary objective was to determine the proportion of asymptomatic COVID-19 cases reported during mass testing interventions.MethodsLiterature in English was searched from September through December 2020 in Google Scholar, ScienceDirect, Mendeley, and PubMed. Search terms included “mass testing,” “test and trace,” “contact tracing,” “COVID-19,” “SARS-CoV-2,” “effectiveness,” “asymptomatic,” “symptomatic,” “community screening,” “UK,” and “2020.” Search results were synthesized without meta-analysis using the direction of effect as the standardized metric and vote counting as the synthesis metric. A statistical synthesis was performed using Stata 14.2. Tabular and graphical methods were used to present findings.ResultsThe literature search yielded 286 articles from Google Scholar, 20 from ScienceDirect, 14 from Mendeley, 27 from PubMed, and 15 through manual search. A total of 35 articles were included in the review, with a sample size of nearly 1 million participants. We found a 76.9% (10/13, 95% CI 46.2%-95.0%; P=.09) majority vote in favor of the intervention under the primary objective. The overall proportion of asymptomatic cases among those who tested positive and in the tested sample populations under the secondary objective was 40.7% (1084/2661, 95% CI 38.9%-42.6%) and 0.0% (1084/9,942,878, 95% CI 0.0%-0.0%), respectively.ConclusionsThere was low-level but promising evidence that mass testing and contact tracing could be more effective in bringing the virus under control and even more effective if combined with social distancing and face coverings. The conventional test and trace method should be superseded by decentralized and regular mass rapid testing and contact tracing, championed by general practitioner surgeries and low-cost community services.

Estimating the extent of asymptomatic COVID-19 and its potential for community transmission: Systematic review and meta-analysis.

Knowing the prevalence of true asymptomatic coronavirus disease 2019 (COVID-19) cases is critical for designing mitigation measures against the pandemic. We aimed to synthesize all available research on asymptomatic cases and transmission rates. We searched PubMed, Embase, Cochrane COVID-19 trials, and Europe PMC for primary studies on asymptomatic prevalence in which (1) the sample frame includes at-risk populations and (2) follow-up was sufficient to identify pre-symptomatic cases. Meta-analysis used fixed-effects and random-effects models. We assessed risk of bias by combination of questions adapted from risk of bias tools for prevalence and diagnostic accuracy studies. We screened 2,454 articles and included 13 low risk-of-bias studies from seven countries that tested 21,708 at-risk people, of which 663 were positive and 111 asymptomatic. Diagnosis in all studies was confirmed using a real-time reverse transcriptase-polymerase chain reaction test. The asymptomatic proportion ranged from 4% to 41%. Meta-analysis (fixed effects) found that the proportion of asymptomatic cases was 17% (95% CI 14% to 20%) overall and higher in aged care (20%; 95% CI 14% to 27%) than in non-aged care (16%; 95% CI 13% to 20%). The relative risk (RR) of asymptomatic transmission was 42% lower than that for symptomatic transmission (combined RR 0.58; 95% CI 0.34 to 0.99, p = 0.047). Our one-in-six estimate of the prevalence of asymptomatic COVID-19 cases and asymptomatic transmission rates is lower than those of many highly publicized studies but still sufficient to warrant policy attention. Further robust epidemiological evidence is urgently needed, including in subpopulations such as children, to better understand how asymptomatic cases contribute to the pandemic.

Epidemiological characteristics and transmission dynamics of paediatric cases with coronavirus disease 2019 in Hubei province, China.

This study aimed to identify the epidemiological characteristics and transmission dynamics of paediatric cases. Information on 1369 paediatric cases with COVID-19 from 8 December 2019 to 7 March 2020 in Hubei province was extracted from the National Infectious Disease Surveillance System. The analysis included epidemic curves, temporal-spatial distribution, clinical classification and interval times between onset and diagnosis. Among 1369 paediatric cases, the median age was 9 years and 58.2% of them were males. The proportion of severe and critical cases in children was lower than that in adults and the proportion of asymptomatic cases in children was five times greater than for adult cases. The first paediatric case was reported on 2 January 2020, and the daily number of new paediatric cases remained high from 1 February through to 22 February. The epidemiological curve of paediatric cases lagged behind that of adults by 19 days, and the first spike of the epidemic curve in senior high school students occurred 1 week earlier than in other paediatric groups. The proportion of clustered cases among children was about twice that for adults. The median of the interval in paediatric cases between onset and diagnosis, isolation and notification were 3, 0 and 3 days, respectively, and all of those were significantly shorter than in adults. The epidemic curve of child cases lagged behind that of adult cases by 19 days, and the major form of transmission observed was in clusters.

Three Quarters of People with SARS-CoV-2 Infection are Asymptomatic: Analysis of English Household Survey Data.

BackgroundTo reduce transmission of SARS-CoV-2, it is important to identify those who are infectious. However, little is known about what proportion of infectious people are asymptomatic and potential “silent” transmitters. We evaluated the value of COVID-19 symptoms as a marker for SARS-CoV-2 infection from a representative English survey.MethodsWe used data from the Office for National Statistics Coronavirus (COVID-19) Infection Survey pilot study. We estimated sensitivity, specificity, the proportion of asymptomatic cases (1 – sensitivity), positive predictive value (PPV) and negative predictive value (NPV) of COVID-19 symptoms as a marker of infection using results of the SARS-CoV-2 test as the “gold standard”.ResultsIn total, there were 36,061 individuals with a SARS-CoV-2 test between 26 April and 27 June 2020. Of these, 625 (1.7%) reported symptoms on the day of the test. There were 115 (0.32%) with a positive SARS-CoV-2 test result. Of the 115, there were 27 (23.5%) who were symptomatic and 88 (76.5%) who were asymptomatic on the day of the test. Focusing on those with specific symptoms (cough, and/or fever, and/or loss of taste/smell), there were 158 (0.43%) with such symptoms on the day of the test. Of the 115 with a positive SARS-CoV-2, there were 16 (13.9%) reporting symptoms. In contrast, 99 (86.1%) did not report specific symptoms on the day of the test. The PPV for all symptoms was 4.3% and for the specific symptoms 10.1%. The specificity and NPV of symptoms were above 98%.ConclusionCOVID-19 symptoms are poor markers of SARS-CoV-2. Thus, 76.5% of this random sample who tested positive reported no symptoms, and 86.1% reported none of those specific to COVID-19. A more widespread testing programme is necessary to capture “silent” transmission and potentially prevent and reduce future outbreaks.

Epidemiology and Control of Two Epidemic Waves of SARS-CoV-2 in South Korea

Background: Since the first case of pandemic COVID-19 in South Korea, identified on 19 January 2020, two epidemic waves have occurred. We characterised the epidemiology, transmission dynamics and effectiveness of control measures in each epidemic wave of COVID-19.Methods: We analysed publicly available data on confirmed cases of COVID-19 outside of Daegu-Gyeongbuk Regions in South Korea during first (19 January–19 April 2020) and second (20 April–11 August 2020) epidemic waves. Transmissibility of SARS-CoV-2 was measured by daily effective reproductive number, Rt. Frequencies of cluster types, age-specific transmission probability matrices, proportion of asymptomatic and unlinked cases, and serial interval distribution were estimated for each wave. Results: In early May, within 2-weeks of relaxation on strict social distancing measures, Rt increased rapidly from 0.2 to 2.3 within a week and was around 1 until early July. The most frequent clusters type were the religious related activities in both waves, but noticed more workplace-related clusters in the second wave. The proportion of asymptomatic cases at presentation increased from 22% during first wave to 27% during second wave. The proportion of unlinked local cases were similar in both waves (22% and 24%). Transmissions among same age were more common, and children were rarely infectors or infectees. The mean serial interval were similar (~3 days) in both waves. Conclusions: Our study shows that relaxing social distancing measures was associated with increased SARS-CoV-2 transmission. Enhanced contact tracing including asymptomatic cases could be more efficient with social distancing to control further waves of the pandemic.

Characteristics of discharged patients from hospitals - Georgian descriptive study

COVID-19, the disease caused by the novel coronavirus, started spreading rapidly across the world. Although, many aspects of disease is still under the observation. Therefore, in this study retrospectively was investigated the data on patients discharged from Georgian hospitals between February and June.According to Georgian regulation, all patients with confirmed COVID-19 should be hospitalized. The data sources were hospitalization registry and the standardized case report forms. In this descriptive study, epidemiological characteristics of 500 COVID-19 cases confirmed with PCR tests were analyzed. Among variables were: gender, age and geographic distribution, disease characteristics, underlying health conditions, test-related features, etc.Majority of patients (72.0%) were admitted to hospitals by the ambulance. The mean age of the patients was 43 years. The sex distribution was merely the same for both genders (49.4% male and 50.6% female). The most common symptoms were fever (82.4%, 95% CI 78.4-85.9), fatigue (49.6%, 95% CI 44.7-54.5), and cough (38.3%, 95% CI 33.6-43.1). The proportion of asymptomatic cases during the PCR testing were 16.6%. More than one symptom was observed in 57.6% of patients. Most common underlying health conditions were cardiovascular diseases (21.8%), diabetes (7.6%), kidney disease (3.6%), chronic lung disease (2.4%), cancer (2.2%), and chronic hepatitis (1.8%). Disease severity significantly differ among cases. Of those without comorbidity conditions, 94% had mild severity. However, among those with comorbidity conditions 35% were sever or critical. 50% of patients were reported as obese. The proportion of severe or critical patients was higher with BMI-18.5-24.9 and BMI ≥30. The case-fatality rate was 2.6%, with majority of deaths among aged ≥70.The severity of illness was strongly associated with comorbidity conditions and BMI. These findings are important to contribute and improve evidence-based knowledge for the novel coronavirus.Key messages Hospitalization of all COVID-19 cases, despite their severity, improving positive outcome of patients.Follow-up for discharged patients is necessary to control medium and long-term impact of COVID-19.

Identifying common baseline clinical features of COVID-19: a scoping review.

ObjectivesOur research question was: what are the most frequent baseline clinical characteristics in adult patients with COVID-19? Our major aim was to identify common baseline clinical features that could help recognise adult patients at high risk of having COVID-19.DesignWe conducted a scoping review of all the evidence available at LitCovid, until 23 March 2020.SettingStudies conducted in any setting and any country were included.ParticipantsStudies had to report the prevalence of sociodemographic characteristics, symptoms and comorbidities specifically in adults with a diagnosis of infection by SARS-CoV-2.ResultsIn total, 1572 publications were published on LitCovid. We have included 56 articles in our analysis, with 89% conducted in China and 75% containing inpatients. Three studies were conducted in North America and one in Europe. Participants’ age ranged from 28 to 70 years, with balanced gender distribution. The proportion of asymptomatic cases were from 2% to 79%. The most common reported symptoms were fever (4%–99%), cough (4%–92%), dyspnoea/shortness of breath (1%–90%), fatigue (4%–89%), myalgia (3%–65%) and pharyngalgia (2%–61%), while regarding comorbidities, we found cardiovascular disease (1%–40%), hypertension (0%–40%) and cerebrovascular disease (1%–40%). Such heterogeneity impaired the conduction of meta-analysis.ConclusionsThe infection by COVID-19 seems to affect people in a very diverse manner and with different characteristics. With the available data, it is not possible to clearly identify those at higher risk of being infected with this condition. Furthermore, the evidence from countries other than China is, at the moment, too scarce.

The clinical characteristics of pediatric inpatients with SARS-CoV-2 infection: A meta-analysis and systematic review.

Millions of people were infected with the coronavirus disease 2019 (COVID‐19) all over the world. Data on clinical symptoms of pediatric inpatients with COVID‐19 infection were unclear. The aim of study was to investigate the clinical features of pediatric inpatients with severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection. PubMed, EMBASE, and the Cochrane Library were searched to seek for studies providing details on pediatric inpatients with SARS‐CoV‐2 infection which were published from 1st January to 21st April 2020. Studies with more than five pediatric inpatients were included in our meta‐analysis.This study was registered in the PROSPERO database (CRD42020183550). As the results shown, fever (46%) and cough (42%) were the main clinical characters of pediatric inpatients with SARS‐CoV‐2 infection and the other clinical characters, such as diarrhea, vomiting, nasal congestion, and fatigue account for 10% in pediatric inpatients. The proportion of asymptomatic cases was 0.42 (95% confidence interval [CI]: 0.27‐0.59) and severe cases was 0.03 (95% CI: 0.01‐0.06). For the laboratory result, leukopenia (21%) and lymphocytosis (22%) were the mainly indicators for pediatric inpatients, followed by high aspartate aminotransferase (19%), lymphopenia (16%), high alanine aminotransferase (15%), high C‐reactive protein (17%), leukocytosis (13%), high D‐dimer (12%) and high creatine kinase‐MB (5%). Regard to chest imaging features, unilateral and bilateral accounts for 22% in pediatric inpatients, respectively. In conclusion, compared with adult inpatients with SARS‐CoV‐2 infection, the pediatric inpatients had mild clinical characters, lab test indicators, and chest imaging features. More clinical studies focus on the pediatric patients with SARS‐CoV‐2 infection in other countries should be conducted.

Conversion of asymptomatic infection to symptomatic visceral leishmaniasis: Astudy of possible immunological markers.

IntroductionPresence of asymptomatic individuals in endemic areas is common. The possible biomarkers in asymptomatic individuals once they get exposed to infection as well as following conversion to symptomatic disease are yet to be identified.We identified asymptomatic Visceral leishmaniasis (VL) infection amongst rK39+sorted direct agglutination test positive (DAT+) endemic healthy population and confirmed it by quantitative PCR(qPCR).The immunological determinants such as Adenosine deaminase (ADA), Interferon gamma (IFN-γ), Tumour Necrosis Factor alpha (TNF-α) and Interleukin 10 (IL-10)were examined to predict probable biomarkers for conversion to symptomatic VL.MethodsSample size was 5794 healthy individuals from VL endemic region. Antibody tests(DAT &rK39) were performed and later a qPCR assay was employed using kDNA specific primers and probes. Immunological biomarkers examined were ADA level by ADA–MTP kit and quantitative cytokines(IFN-γ, IL-10 and TNF-α) by ELISA.Results120 asymptomatic individuals of 308 rK39 sero-positives were DAT positive comprising of 56 with previous history and 64 with no history of VL. RT-PCR confirmed asymptomatic VL in 42 sero-positives. These were followed up through repeated qPCR and evaluation of immunological determinants. We observed10 symptomatic cases converted from a total of 42 asymptomatic individuals identified at base-line. The level of ADA, IL-10 and IFN-γ remained consistently high in asymptomatic cases and amongst these, ADA and IL-10 but not IFN-γ remained higher at the development of clinical symptoms into active VL. On the contrary, there was no significant change in the mean concentration of TNF-α at both stages of the disease.DiscussionWe surmise from our data that considerable proportion of asymptomatic cases can be a reservoir and may play a crucial role in transmission of visceral leishmaniasis in endemic areas.The data also suggests that ADA and IL-10 can serve as a potential biomarker during the conversion of asymptomatic into symptomatic VL.

Effectiveness of Isolation and Contact Tracing for Containment and Slowing Down a COVID-19 Epidemic: A Modelling Study

Background: Novel coronavirus (SARS-CoV-2) is extending its range of transmission in all parts of the world, with substantial variation in rates of transmission and severity of associated disease. Methods: We evaluated whether and under which conditions it is possible to control and slow down a COVID-19 epidemic in the early stages by isolation and contact tracing. We used a stochastic transmission model in which every person generates novel infections according to a probability distribution that is affected by the incubation period distribution (time from infection to symptoms), distribution of the latent period (time from infection to a person becoming infectious), and overall transmissibility. The model distinguishes between close contacts (e.g., within a household) and other contacts in the population. Findings: The analyses showed that transmissibility and the duration of the latent period relative to the duration of incubation period have strong impact on the controllability of the disease. Delays in diagnosis of cases and proportion of asymptomatic cases are key factors for containment and slowing down the epidemic. Interpretation: Isolation and contact tracing can be an effective means to control early epidemics, but only if transmissibility as measured by R0 is in the lower ranges of reported values. Timeliness as well as completeness of tracing and diagnosis of cases are paramount to achieve containment and effective slowing down of the epidemic growth rate. Funding Statement: This research was funded by the Dutch Ministry of Health, Welfare and Sport and by ZonMw project number 91216062. Declaration of Interests: The authors declare no competing interests.

INFLUENCE OF ASYMPTOMATIC PEOPLE ON MALARIA TRANSMISSION: A MATHEMATICAL MODEL FOR A LOW-TRANSMISSION AREA CASE

Malaria remains a primary parasitic disease in the tropical world, generating high morbidity and mortality in human populations. Recently, community surveys showed a high proportion of asymptomatic cases, which are characterized by a low parasitemia and a lack of malaria symptoms. Until now, the asymptomatic population is not treated for malaria and thus remains infective for a long time. In this paper, we introduce a four-dimensional mathematical model to study the influence of asymptomatic people on malaria transmission in low-transmission areas, specifically using data from Brazil. The equilibrium points of the system are calculated, and their stability is analyzed. Via numerical simulations, more in-depth analyzes of the space of some crucial parameters on the asymptomatic population are done, such as the per capita recovery rates of symptomatic and asymptomatic people, the ratio of the density of mosquitoes to that of humans, the mortality rate of mosquitoes and the probability of undergoing asymptomatic infection upon an infectious mosquito bite. Our results indicate that the disease-free equilibrium is inside the stability region if asymptomatic people are treated and/or the ratio of the density of mosquitoes to that of humans is decreased and/or the mortality rate of mosquitoes is increased.

Effectiveness of airport screening at detecting travellers infected with novel coronavirus (2019-nCoV).

We evaluated effectiveness of thermal passenger screening for 2019-nCoV infection at airport exit and entry to inform public health decision-making. In our baseline scenario, we estimated that 46% (95% confidence interval: 36 to 58) of infected travellers would not be detected, depending on incubation period, sensitivity of exit and entry screening, and proportion of asymptomatic cases. Airport screening is unlikely to detect a sufficient proportion of 2019-nCoV infected travellers to avoid entry of infected travellers.