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PloS One 2021The Covid-19 pandemic has spread across the world since the beginning of 2020. Many regions have experienced its effects. The state of South Carolina in the USA has seen...
The Covid-19 pandemic has spread across the world since the beginning of 2020. Many regions have experienced its effects. The state of South Carolina in the USA has seen cases since early March 2020 and a primary peak in early April 2020. A lockdown was imposed on April 6th but lifting of restrictions started on April 24th. The daily case and death data as reported by NCHS (deaths) via the New York Times GitHUB repository have been analyzed and approaches to modeling of the data are presented. Prediction is also considered and the role of asymptomatic transmission is assessed as a latent unobserved effect. Two different time periods are examined and one step prediction is provided. The results suggest that both socio-economic disadvantage, asymptomatic transmission and spatial confounding are important ingredients in any model pertaining to county level case dynamics.
Topics: Asymptomatic Infections; Bayes Theorem; COVID-19; Humans; Pandemics; Physical Distancing; Quarantine; SARS-CoV-2; South Carolina
PubMed: 33730035
DOI: 10.1371/journal.pone.0242777 -
PloS One 2023Testing remains a key tool for managing health care and making health policy during the coronavirus pandemic, and it will probably be important in future pandemics....
Testing remains a key tool for managing health care and making health policy during the coronavirus pandemic, and it will probably be important in future pandemics. Because of false negative and false positive tests, the observed fraction of positive tests-the surface positivity-is generally different from the fraction of infected individuals (the incidence rate of the disease). In this paper a previous method for translating surface positivity to a point estimate for incidence rate, then to an appropriate range of values for the incidence rate consistent with the model and data (the test range), and finally to the risk (the probability of including one infected individual) associated with groups of different sizes is illustrated. The method is then extended to include asymptomatic infections. To do so, the process of testing is modeled using both analysis and Monte Carlo simulation. Doing so shows that it is possible to determine point estimates for the fraction of infected and symptomatic individuals, the fraction of uninfected and symptomatic individuals, and the ratio of infected asymptomatic individuals to infected symptomatic individuals. Inclusion of symptom status generalizes the test range from an interval to a region in the plane determined by the incidence rate and the ratio of asymptomatic to symptomatic infections; likelihood methods can be used to determine the contour of the rest region. Points on this contour can be used to compute the risk (defined as the probability of including one asymptomatic infected individual) in groups of different sizes. These results have operational implications that include: positivity rate is not incidence rate; symptom status at testing can provide valuable information about asymptomatic infections; collecting information on time since putative virus exposure at testing is valuable for determining point estimates and test ranges; risk is a graded (rather than binary) function of group size; and because the information provided by testing becomes more accurate with more tests but at a decreasing rate, it is possible to over-test fixed spatial regions. The paper concludes with limitations of the method and directions for future work.
Topics: Humans; COVID-19; Asymptomatic Infections; SARS-CoV-2; Viruses; Forecasting
PubMed: 36780871
DOI: 10.1371/journal.pone.0281710 -
Malaria Journal Jun 2022High levels of genetic diversity are common characteristics of Plasmodium falciparum parasite populations in high malaria transmission regions. There has been a decline...
Maintenance of high temporal Plasmodium falciparum genetic diversity and complexity of infection in asymptomatic and symptomatic infections in Kilifi, Kenya from 2007 to 2018.
BACKGROUND
High levels of genetic diversity are common characteristics of Plasmodium falciparum parasite populations in high malaria transmission regions. There has been a decline in malaria transmission intensity over 12 years of surveillance in the community in Kilifi, Kenya. This study sought to investigate whether there was a corresponding reduction in P. falciparum genetic diversity, using msp2 as a genetic marker.
METHODS
Blood samples were obtained from children (< 15 years) enrolled into a cohort with active weekly surveillance between 2007 and 2018 in Kilifi, Kenya. Asymptomatic infections were defined during the annual cross-sectional blood survey and the first-febrile malaria episode was detected during the weekly follow-up. Parasite DNA was extracted and successfully genotyped using allele-specific nested polymerase chain reactions for msp2 and capillary electrophoresis fragment analysis.
RESULTS
Based on cross-sectional surveys conducted in 2007-2018, there was a significant reduction in malaria prevalence (16.2-5.5%: P-value < 0.001), however msp2 genetic diversity remained high. A high heterozygosity index (He) (> 0.95) was observed in both asymptomatic infections and febrile malaria over time. About 281 (68.5%) asymptomatic infections were polyclonal (> 2 variants per infection) compared to 46 (56%) polyclonal first-febrile infections. There was significant difference in complexity of infection (COI) between asymptomatic 2.3 [95% confidence interval (CI) 2.2-2.5] and febrile infections 2.0 (95% CI 1.7-2.3) (P = 0.016). Majority of asymptomatic infections (44.2%) carried mixed alleles (i.e., both FC27 and IC/3D7), while FC27 alleles were more frequent (53.3%) among the first-febrile infections.
CONCLUSIONS
Plasmodium falciparum infections in Kilifi are still highly diverse and polyclonal, despite the reduction in malaria transmission in the community.
Topics: Antigens, Protozoan; Asymptomatic Infections; Child; Cross-Sectional Studies; Fever; Genetic Variation; Genotype; Humans; Kenya; Malaria, Falciparum; Plasmodium falciparum; Protozoan Proteins
PubMed: 35725456
DOI: 10.1186/s12936-022-04213-7 -
PloS One 2023Asymptomatic malaria infections have received less attention than symptomatic malaria infections in major studies. Few epidemiological studies on asymptomatic malaria...
BACKGROUND
Asymptomatic malaria infections have received less attention than symptomatic malaria infections in major studies. Few epidemiological studies on asymptomatic malaria infections have often focused on pregnant women and children under-five years of age as the most vulnerable groups. However, there is limitation on data regarding asymptomatic infections among the old adult populations, particularly in the study area. Therefore, this study determined the prevalence of asymptomatic malaria infection by microscopy and its determinants among residents of Ido- Ekiti, Southwestern Nigeria.
METHODS
A hospital-based cross-sectional study was conducted between July and September 2021 among 232 consenting apparently healthy individuals aged 40 years and above who were recruited during a free health screening program using a standardised interviewer-administered questionnaire. The questionnaire sought information on respondents' socio-demographics, presence and types of co-morbidity, and the prevention methods being adopted against malaria infection. Venous blood samples were collected and processed for asymptomatic infections using Giemsa-stained blood smear microscopy. Data were analysed using SPSS version 21. Multivariate logistic regression was used to identify factors associated with asymptomatic infections.
RESULTS
Of the total 232 respondents, 19.0% (48/232) were confirmed to be infected with Plasmodium falciparum (95% confidence interval (CI): 14.1% - 24.6%). Lack of formal education (Adjusted odds ratio (AOR): 5.298, 95% (CI): 2.184-13.997), being diabetic (AOR: 4.681, 95% CI: 1.669-16.105), and not sleeping under Long Lasting Insecticide Net (LLINs) (AOR: 4.594, 95% CI: 1.194-14.091), were the determinants of asymptomatic Plasmodium falciparum infection.
CONCLUSION
The prevalence of asymptomatic Plasmodium falciparum was 19%. Lack of formal education, being diabetic, and not sleeping under LLINs were the determinants of asymptomatic infections.
Topics: Adult; Child; Female; Humans; Pregnancy; Cross-Sectional Studies; Prevalence; Asymptomatic Infections; Microscopy; Nigeria; Malaria; Malaria, Falciparum; Plasmodium falciparum; Diabetes Mellitus
PubMed: 36787321
DOI: 10.1371/journal.pone.0280981 -
Talanta Mar 2022Asymptomatic infection of COVID-19 is a global threat for public health. Unfortunately, the study about metabolic dysregulation of asymptomatic infection is barely...
Asymptomatic infection of COVID-19 is a global threat for public health. Unfortunately, the study about metabolic dysregulation of asymptomatic infection is barely investigated. Here, we performed carboxylic submetabolome profiling of serum from 62 asymptomatic and 122 control individuals, by a highly sensitive chemical isotope labelling method. Twenty-one discriminative carboxylic features, including 12-hydroxyeicosatetraenoic acid, cholic acid, glycoursodeoxycholic acid and 15,16-dihydroxyoctadeca-9,12-dienoic acid were discovered to be dysregulated in asymptomatic patients. This panel containing 21 carboxylic features could accurately identify asymptomatic patients based on a random forest model, providing an accuracy of 85.7% with only 3.6% false positive rate and 7.1% false negative rate. The dysregulated metabolites found in asymptomatic patients covered several important pathways, such as arachidonic acid metabolism, synthesis of bile acid, β-oxidation of fatty acids, activation of macrophage and platelet aggregation. This work provided valuable knowledge about serum biomarkers and molecular clues associated with asymptomatic COVID-19 patients.
Topics: Asymptomatic Infections; COVID-19; Fatty Acids; Humans; Isotope Labeling; SARS-CoV-2
PubMed: 34871866
DOI: 10.1016/j.talanta.2021.123086 -
PloS One 2020The aims of this study were to investigate the prevalence and proportion of laboratory-confirmed urethral Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG)...
The aims of this study were to investigate the prevalence and proportion of laboratory-confirmed urethral Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) infections that were asymptomatic among individuals presenting to clinics in Shenzhen and the risk factors related to asymptomatic CT infection. In a cross-sectional study, eligible individuals were invited to participate in the questionnaire, and urine specimens were collected to identify CT and NG infections using a nucleic acid amplification test (NAAT). Considering the differences in the presentation of symptoms between men and women, this study was stratified by gender. Corresponding outcomes were analyzed by Chi-square test and multivariate logistic regression. A total of 2,871 participants were asymptomatic and included in our analyses: 1120 (39.0%) men and 1751 (61.0%) women. The prevalence of asymptomatic NG and CT infections was 0.9% and 6.2% in men, and 0.4% and 7.9% in women, respectively. The proportion of asymptomatic urethral CT among men with urethral CT was 28.3%; for women, it was 34.2%. For asymptomatic men with CT, 3 independent risk factors were identified: (1) men under the age of 30 (aOR, 1.83; 95% CI, 1.11-3.03); (2) being employed in the commercial service work (2.82; 1.36-5.84); and (3) being recruited through the urological department (2.12; 1.19-3.79). For asymptomatic women with urethral CT, age less than 30 years was a risk factor. In conclusion, a substantial prevalence of asymptomatic CT infections was found among men and women presenting to clinics in Shenzhen. The significant correlation between asymptomatic CT infection and these risk factors could help identify high-risk populations and guide screening.
Topics: Adult; Ambulatory Care Facilities; Asymptomatic Infections; China; Chlamydia Infections; Chlamydia trachomatis; Cross-Sectional Studies; Female; Gonorrhea; Humans; Male; Neisseria gonorrhoeae; Prevalence; Risk Factors; Sex Distribution
PubMed: 32516318
DOI: 10.1371/journal.pone.0234261 -
JAMA Internal Medicine Nov 2020There is limited information about the clinical course and viral load in asymptomatic patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
Clinical Course and Molecular Viral Shedding Among Asymptomatic and Symptomatic Patients With SARS-CoV-2 Infection in a Community Treatment Center in the Republic of Korea.
IMPORTANCE
There is limited information about the clinical course and viral load in asymptomatic patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
OBJECTIVE
To quantitatively describe SARS-CoV-2 molecular viral shedding in asymptomatic and symptomatic patients.
DESIGN, SETTING, AND PARTICIPANTS
A retrospective evaluation was conducted for a cohort of 303 symptomatic and asymptomatic patients with SARS-CoV-2 infection between March 6 and March 26, 2020. Participants were isolated in a community treatment center in Cheonan, Republic of Korea.
MAIN OUTCOMES AND MEASURES
Epidemiologic, demographic, and laboratory data were collected and analyzed. Attending health care personnel carefully identified patients' symptoms during isolation. The decision to release an individual from isolation was based on the results of reverse transcription-polymerase chain reaction (RT-PCR) assay from upper respiratory tract specimens (nasopharynx and oropharynx swab) and lower respiratory tract specimens (sputum) for SARS-CoV-2. This testing was performed on days 8, 9, 15, and 16 of isolation. On days 10, 17, 18, and 19, RT-PCR assays from the upper or lower respiratory tract were performed at physician discretion. Cycle threshold (Ct) values in RT-PCR for SARS-CoV-2 detection were determined in both asymptomatic and symptomatic patients.
RESULTS
Of the 303 patients with SARS-CoV-2 infection, the median (interquartile range) age was 25 (22-36) years, and 201 (66.3%) were women. Only 12 (3.9%) patients had comorbidities (10 had hypertension, 1 had cancer, and 1 had asthma). Among the 303 patients with SARS-CoV-2 infection, 193 (63.7%) were symptomatic at the time of isolation. Of the 110 (36.3%) asymptomatic patients, 21 (19.1%) developed symptoms during isolation. The median (interquartile range) interval of time from detection of SARS-CoV-2 to symptom onset in presymptomatic patients was 15 (13-20) days. The proportions of participants with a negative conversion at day 14 and day 21 from diagnosis were 33.7% and 75.2%, respectively, in asymptomatic patients and 29.6% and 69.9%, respectively, in symptomatic patients (including presymptomatic patients). The median (SE) time from diagnosis to the first negative conversion was 17 (1.07) days for asymptomatic patients and 19.5 (0.63) days for symptomatic (including presymptomatic) patients (P = .07). The Ct values for the envelope (env) gene from lower respiratory tract specimens showed that viral loads in asymptomatic patients from diagnosis to discharge tended to decrease more slowly in the time interaction trend than those in symptomatic (including presymptomatic) patients (β = -0.065 [SE, 0.023]; P = .005).
CONCLUSIONS AND RELEVANCE
In this cohort study of symptomatic and asymptomatic patients with SARS-CoV-2 infection who were isolated in a community treatment center in Cheonan, Republic of Korea, the Ct values in asymptomatic patients were similar to those in symptomatic patients. Isolation of asymptomatic patients may be necessary to control the spread of SARS-CoV-2.
Topics: Adult; Asymptomatic Infections; COVID-19; COVID-19 Testing; Epidemiological Monitoring; Female; Hospitals, Isolation; Humans; Male; Patient Isolation; Public Health; Republic of Korea; Retrospective Studies; SARS-CoV-2; Symptom Assessment; Viral Load; Virus Shedding
PubMed: 32780793
DOI: 10.1001/jamainternmed.2020.3862 -
The Cochrane Database of Systematic... Jul 2015Gastric cancer is the third most common cause of cancer death worldwide. Individuals infected with Helicobacter pylori have a higher likelihood of developing gastric... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Gastric cancer is the third most common cause of cancer death worldwide. Individuals infected with Helicobacter pylori have a higher likelihood of developing gastric cancer than individuals who are not infected. Eradication of H. pylori in healthy asymptomatic individuals in the general population may reduce the incidence of gastric cancer, but the magnitude of this effect is unclear.
OBJECTIVES
To assess the effectiveness of eradication of H. pylori in healthy asymptomatic individuals in the general population in reducing the incidence of gastric cancer.
SEARCH METHODS
We identified trials by searching the Cochrane Central Register of Controlled Trials (CENTRAL; 2013, Issue 11), MEDLINE (1946 to December 2013), and EMBASE (1974 to December 2013). We handsearched reference lists from trials selected by electronic searching to identify further relevant trials. We handsearched published abstracts from conference proceedings from the United European Gastroenterology Week (published in Gut) and Digestive Disease Week (published in Gastroenterology) between 2001 and 2013. We contacted members of the Cochrane Upper Gastrointestinal and Pancreatic Diseases Review Group and experts in the field and asked them to provide details of outstanding clinical trials and any relevant unpublished materials.
SELECTION CRITERIA
We analysed randomised controlled trials comparing at least one week of H. pylori therapy with placebo or no treatment in preventing subsequent development of gastric cancer in otherwise healthy and asymptomatic H. pylori-positive adults. Trials had to follow up participants for at least two years and needed to have at least two participants with gastric cancer as an outcome. We defined gastric cancer as any gastric adenocarcinoma, including intestinal (differentiated) or diffuse (undifferentiated) type, with or without specified histology.
DATA COLLECTION AND ANALYSIS
We collected data on incidence of gastric cancer, incidence of oesophageal cancer, deaths from gastric cancer, deaths from any cause, and adverse effects arising due to therapy.
MAIN RESULTS
Six trials met all our eligibility criteria and provided extractable data. Three trials were at low risk of bias, one trial was at unclear risk, and two trials were at high risk of bias. Five trials were conducted in Asian populations. In preventing development of subsequent gastric cancer, H. pylori eradication therapy was superior to placebo or no treatment (6 trials, 6497 participants, risk ratio (RR) of developing subsequent gastric cancer 0.66; 95% confidence interval (CI) 0.46 to 0.95; moderate-quality evidence). Only one trial reported effect of eradication of H. pylori on development of subsequent oesophageal cancer (2 (0.2%) among 817 participants assigned to eradication therapy, compared with 1 (0.1%) of 813 participants allocated to placebo; RR 1.99; 95% CI 0.18 to 21.91). The effect of H. pylori eradication on preventing death from gastric cancer compared with placebo or no treatment was uncertain due to wide confidence intervals (3 trials, 4475 participants, RR 0.67; 95% CI 0.40 to 1.11; moderate-quality evidence). There was no evidence of an effect on all-cause mortality (4 trials, 5253 participants, RR 1.09; 95% CI 0.86 to 1.38; moderate-quality evidence). Adverse events data were poorly reported.
AUTHORS' CONCLUSIONS
We found limited, moderate-quality evidence that searching for and eradicating H. pylori reduces the incidence of gastric cancer in healthy asymptomatic infected Asian individuals, but we cannot necessarily extrapolate this data to other populations.
Topics: Anti-Bacterial Agents; Anti-Ulcer Agents; Asymptomatic Infections; Drug Therapy, Combination; Helicobacter Infections; Helicobacter pylori; Humans; Precancerous Conditions; Randomized Controlled Trials as Topic; Stomach Neoplasms
PubMed: 26198377
DOI: 10.1002/14651858.CD005583.pub2 -
JAMA Jun 2021This study aims to describe an association between the Pfizer-BioNTech (BNT162b2) vaccine and decreased risk of symptomatic and asymptomatic infections with SARS-CoV-2...
This study aims to describe an association between the Pfizer-BioNTech (BNT162b2) vaccine and decreased risk of symptomatic and asymptomatic infections with SARS-CoV-2 in hospital employees.
Topics: Adult; Aged; Asymptomatic Infections; BNT162 Vaccine; COVID-19; COVID-19 Vaccines; Female; Humans; Male; Mass Screening; Middle Aged; Personnel, Hospital; Retrospective Studies
PubMed: 33956050
DOI: 10.1001/jama.2021.6564 -
The Journal of Emergency Medicine Sep 2022High rates of asymptomatic infections with COVID-19 have been reported.
BACKGROUND
High rates of asymptomatic infections with COVID-19 have been reported.
OBJECTIVE
We aimed to describe an asymptomatic COVID-19 testing protocol in a pediatric emergency department (ED).
METHODS
This was a retrospective cohort study of pediatric patients (younger than 18 years) who were tested for COVID-19 via the asymptomatic testing protocol at a single urban pediatric ED between May 2020 and January 2021. This included all pediatric patients undergoing admission, urgent procedures, and psychiatric facility placement. The primary outcome was the percentage of positive COVID-19 tests. COVID-19 testing was performed via real-time polymerase chain reaction RNA assay testing. County-level COVID-19 data were used to estimate local daily COVID-19 cases/100,000 individuals (from all ages). Data were described with simple descriptive statistics.
RESULTS
There were 1459 children tested for COVID-19 under the asymptomatic protocol. Mean ± standard deviation age was 8.2 ± 5.8 years. Two tests were inconclusive and 29 (2.0%; 95% confidence interval [CI] 1.3-2.8%) were positive. Of the 29 positive cases, 14 (48%; 95% CI 29-67%) had abnormal vital signs or signs and symptoms of COVID-19, on retrospective review. A total of 15 truly asymptomatic infections were identified. On the days that asymptomatic cases were identified, the lowest average daily community rate was 7.67 cases/100,000 individuals.
CONCLUSIONS
Asymptomatic COVID-19 positivity rates in the pediatric ED were low when the average daily community rate was fewer than 7.5 cases/100,000 individuals. In the current pandemic, ED clinicians should assess for signs and symptoms of COVID-19, even when children present to the ED with unrelated chief symptoms.
Topics: Humans; Child; Child, Preschool; Adolescent; COVID-19; COVID-19 Testing; Asymptomatic Infections; SARS-CoV-2; Retrospective Studies; Emergency Service, Hospital
PubMed: 35400507
DOI: 10.1016/j.jemermed.2022.01.015