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Mathematical Biosciences and... Nov 2020Asymptomatic transmission of infectious diseases has been recognized recently in several epidemics or pandemics. There is a great need to incorporate asymptomatic...
Asymptomatic transmission of infectious diseases has been recognized recently in several epidemics or pandemics. There is a great need to incorporate asymptomatic transmissions into traditional modeling of infectious diseases and to study how asymptomatic transmissions shift epidemic dynamics. In this work, we propose a compartmental model with asymptomatic transmissions for waterborne infectious diseases. We conduct a detailed analysis and numerical study with shigellosis data. Two parameters, the proportion $p$ of asymptomatic infected individuals and the proportion $k$ of asymptomatic infectious individuals who can asymptomatically transmit diseases, play major rules in the epidemic dynamics. The basic reproduction number $\mathscr{R}_{0}$ is a decreasing function of parameter $p$ when parameter $k$ is smaller than a critical value while $\mathscr{R}_{0}$ is an increasing function of $p$ when $k$ is greater than the critical value. $\mathscr{R}_{0}$ is an increasing function of $k$ for any value of $p$. When $\mathscr{R}_{0}$ passes through 1 as $p$ or $k$ varies, the dynamics of epidemics is shifted. If asymptomatic transmissions are not counted, $\mathscr{R}_{0}$ will be underestimated while the final size may be overestimated or underestimated. Our study provides a theoretical example for investigating other asymptomatic transmissions and useful information for public health measurements in waterborne infectious diseases.
Topics: Asymptomatic Infections; Basic Reproduction Number; Communicable Diseases; Epidemics; Humans; Pandemics
PubMed: 33525082
DOI: 10.3934/mbe.2021005 -
Reumatologia Clinica May 2021Uric acid has been related to a tendency to precipitate to form crystals, presenting asymptomatically, until the formation of arthritis, tophi or renal lithiasis....
BACKGROUND
Uric acid has been related to a tendency to precipitate to form crystals, presenting asymptomatically, until the formation of arthritis, tophi or renal lithiasis. Previously, the presence of asymptomatic hyperuricaemia has been associated with the presence of cardiovascular disease.
OBJECTIVES
To determine the association of complex coronary artery disease in patients with asymptomatic hyperuricaemia.
MATERIAL AND METHODS
An observational retrospective, transversal, unicentric study was conducted in a tertiary hospital in Mexico, in the period from June 2017 to March 2019. All patients admitted for coronary angiography were included; patients with gout, use of diuretics and chronic kidney disease were excluded.
RESULTS
During the study period, a total of 300 patients were collected, of which 40% presented hyperuricaemia. The patients with hyperuricaemia were older (59 vs. 63, P = .002). The group of patients with asymptomatic hyperuricaemia had a higher proportion of complex coronary lesions (64 vs. 35%, P ≤ .0001) as well as a higher SYNTAX I score (27 vs. 17, P ≤ .001). There was a higher probability of presenting complex coronary lesions in this group of patients (OR 3.4, P ≤ .0001). In addition, in the group division of uric acid levels, it was related to the presence of complex coronary lesions (Q1 = .5, P = .06), (Q2 = 2, P = .01) and (Q3 = 3, P ≤ .0001).
CONCLUSION
Asymptomatic hyperuricaemia has a higher prevalence and association of presenting complex coronary lesions.
PubMed: 31707094
DOI: 10.1016/j.reuma.2019.08.003 -
Modern Rheumatology Case Reports Jan 2021A 33-year-old male with a history of bronchial asthma and allergic rhinitis was diagnosed with eosinophilic granulomatosis with polyangiitis (EGPA) eight years ago. The... (Review)
Review
A 33-year-old male with a history of bronchial asthma and allergic rhinitis was diagnosed with eosinophilic granulomatosis with polyangiitis (EGPA) eight years ago. The diagnosis was based on the presence of fever, remarkable eosinophilia, and painful digital ulcer. His signs and symptoms improved with a moderate dose of glucocorticoids. Thereafter, he was lost to follow-up, failing to attend any of the scheduled appointments. Three years later, he presented with painful digital gangrene on the lateral fold of the right ring fingernail and abdominal pain triggered by meals. Angiography showed multiple occlusions and severe stenoses of the peripheral arteries and coronary aneurysms, which confirmed the diagnosis of medium vessel vasculitis of the coronary and peripheral arteries due to flare up of EGPA. EGPA predominantly affects the small-sized vessels, but rarely the medium-sized vessels. Coronary vasculitis might occur asymptomatically, until the coronary stenosis becomes severe or myocardial infarction develops; hence, its prevalence is underestimated. In this case, a digital gangrene prompted us to perform a systemic angiography, leading to the diagnosis of coronary vasculitis. Careful observation for coronary lesions is necessary in patients with EGPA who develop digital gangrene.
Topics: Adult; Churg-Strauss Syndrome; Coronary Aneurysm; Coronary Angiography; Fingers; Gangrene; Humans; Male
PubMed: 32791887
DOI: 10.1080/24725625.2020.1810404 -
Expert Review of Anti-infective Therapy Aug 2014Clostridium difficile (CD) infection (CDI) is the leading cause of healthcare associated diarrhea despite intense hospital infection prevention programs. A substantial... (Review)
Review
Clostridium difficile (CD) infection (CDI) is the leading cause of healthcare associated diarrhea despite intense hospital infection prevention programs. A substantial proportion of the population is asymptomatically colonized with CD, and evidence is mounting that these individuals serve as a reservoir for CDI. The purpose of this review is to discuss the mechanisms by which individuals may harbor toxigenic CD but remain asymptomatic, the evidence that asymptomatically colonized individuals serve as a source of CDI, and the implications of this potential CD reservoir for healthcare infection prevention.
Topics: Animals; Carrier State; Clostridioides difficile; Disease Reservoirs; Enterocolitis, Pseudomembranous; Genotyping Techniques; Humans
PubMed: 24848084
DOI: 10.1586/14787210.2014.920252 -
BMJ Open May 2021The aim of this study was to determine the relative infectiousness of asymptomatic SARS-CoV-2 infected persons compared with symptomatic individuals based on a scoping... (Review)
Review
OBJECTIVES
The aim of this study was to determine the relative infectiousness of asymptomatic SARS-CoV-2 infected persons compared with symptomatic individuals based on a scoping review of available literature.
DESIGN
Rapid scoping review of peer-reviewed literature from 1 January to 5 December 2020 using the LitCovid database and the Cochrane library.
SETTING
International studies on the infectiousness of individuals infected with SARS-CoV-2.
PARTICIPANTS
Studies were selected for inclusion if they defined asymptomatics as a separate cohort distinct from presymptomatics and if they provided a quantitative measure of the infectiousness of asymptomatics relative to symptomatics.
PRIMARY OUTCOME MEASURES
PCR result (PCR studies), the rate of infection (mathematical modelling studies) and secondary attack rate (contact tracing studies) - in each case from asymptomatic in comparison with symptomatic individuals.
RESULTS
There are only a limited number of published studies that report estimates of relative infectiousness of asymptomatic compared with symptomatic individuals. 12 studies were included after the screening process. Significant differences exist in the definition of infectiousness. PCR studies in general show no difference in shedding levels between symptomatic and asymptomatic individuals; however, the number of study subjects is generally limited. Two modelling studies estimate relative infectiousness to be 0.43 and 0.57, but both of these were more reflective of the infectiousness of undocumented rather than asymptomatic cases. The results from contact tracing studies include estimates of relative infectiousness of 0, but with insufficient evidence to conclude that it is significantly different from 1.
CONCLUSIONS
There is considerable heterogeneity in estimates of relative infectiousness highlighting the need for further investigation of this important parameter. It is not possible to provide any conclusive estimate of relative infectiousness, as the estimates from the reviewed studies varied between 0 and 1.
Topics: COVID-19; Cohort Studies; Contact Tracing; Humans; Mass Screening; SARS-CoV-2
PubMed: 33947725
DOI: 10.1136/bmjopen-2020-042354 -
Clinical Microbiology and Infection :... Feb 2022The role of SARS-Cov-2-infected persons who develop symptoms after testing (presymptomatics) or not at all (asymptomatics) in the pandemic spread is unknown. (Review)
Review
BACKGROUND
The role of SARS-Cov-2-infected persons who develop symptoms after testing (presymptomatics) or not at all (asymptomatics) in the pandemic spread is unknown.
OBJECTIVES
To determine infectiousness and probable contribution of asymptomatic persons (at the time of testing) to pandemic SARS-CoV-2 spread.
DATA SOURCES
LitCovid, medRxiv, Google Scholar, and WHO Covid-19 databases (to 31 March 2021) and references in included studies.
STUDY ELIGIBILITY CRITERIA
Studies with a proven or hypothesized transmission chain based either on serial PCR cycle threshold readings and/or viral culture and/or gene sequencing, with adequate follow-up.
PARTICIPANTS
People exposed to SARS-CoV-2 within 2-14 days to index asymptomatic (at time of observation) infected individuals.
INTERVENTIONS
Reliability of symptom and signs was assessed within contemporary knowledge; transmission likelihood was assessed using adapted causality criteria.
METHODS
Systematic review. We contacted all included studies' corresponding authors requesting further details.
RESULTS
We included 18 studies from a diverse setting with substantial methodological variation (this field lacks standardized methodology). At initial testing, prevalence of asymptomatic cases was 12.5-100%. Of these, 6-100% were later determined to be presymptomatic, this proportion varying according to setting, methods of case ascertainment and population. Nursing/care home facilities reported high rates of presymptomatic: 50-100% (n = 3 studies). Fourteen studies were classified as high risk of, and four studies as at moderate risk of symptom ascertainment bias. High-risk studies may be less likely to distinguish between presymptomatic and asymptomatic cases. Six asymptomatic studies and four presymptomatic studies reported culturing infectious virus; data were too sparse to determine infectiousness duration. Three studies provided evidence of possible and three of probable/likely asymptomatic transmission; five studies provided possible and two probable/likely presymptomatic SARS-CoV-2 transmission.
CONCLUSION
High-quality studies provide probable evidence of SARS-CoV-2 transmission from presymptomatic and asymptomatic individuals, with highly variable estimated transmission rates.
Topics: Bias; COVID-19; Humans; Pandemics; Reproducibility of Results; SARS-CoV-2
PubMed: 34757116
DOI: 10.1016/j.cmi.2021.10.015 -
Virus Research Feb 2021Melon is one of the most popular fruits worldwide and has been bred into various cultivars. RNA-sequencing using healthy melon fruit was performed to determine...
Melon is one of the most popular fruits worldwide and has been bred into various cultivars. RNA-sequencing using healthy melon fruit was performed to determine differences in gene expression among cultivars. Unexpected RNA-seq results revealed that viruses asymptomatically infected fruits at a high frequency (16 of 21 fruits examined were infected) and that viral transcripts highly accumulated in comparison with host transcripts (15 %-75 % of total reads). Their nucleotide sequences and phylogenetic analyses indicated that more than 10 novel isolates of tobacco ringspot virus (TRSV) were found in melon fruits. Asymptomatic infection with TRSV on melon fruits was confirmed by both immunoblot and RT-PCR analyses. Numerous isolates of TRSV generated and maintained in melon fields, and this is likely due to their asymptomatic infections. This TRSV melon isolate infected Nicotiana benthamiana plants with stunting and yellowing symptoms. This is the first report of frequent and asymptomatic infection of TRSV in consumable melon fruits.
Topics: Cucurbitaceae; Fruit; Nepovirus; Phylogeny; Plant Diseases
PubMed: 33347906
DOI: 10.1016/j.virusres.2020.198266 -
Oral Surgery, Oral Medicine, Oral... Jan 2008The aim of this study was to investigate the rate of herpes simplex virus (HSV) shedding from the oral cavity, because recent studies suggest that shedding is more... (Review)
Review
OBJECTIVE
The aim of this study was to investigate the rate of herpes simplex virus (HSV) shedding from the oral cavity, because recent studies suggest that shedding is more frequent than originally reported. Factors that could influence the rate and duration of shedding from the oral cavity were examined.
METHODS
Existing epidemiologic data from 22 reports of HSV shedding from more than 3,500 individuals were analyzed with regard to demographics, frequency of sampling, and methodologic assays.
RESULTS
HSV-1 was more likely to be detected than HSV-2 in the oral cavity of asymptomatic persons (7.5 odds ratio, 95% confidence interval 4.4-12.8; P < .0001). The rate of shedding was highly variable among individuals, ranging from none to 92% of days tested, and occurred in seropositive and seronegative individuals. In cell culture studies, the rate of detection on a single day was 6.3%. Polymerase chain reaction studies provided a different picture. HSV-1 DNA was present in 97 of 180 patients (53.9%) at multiple visits, with a rate of daily detection of 33.3%. The mean duration of shedding was between 1 and 3 days, but more than 3 days in about 10% of patients.
CONCLUSIONS
At least 70% of the population shed HSV-1 asymptomatically at least once a month, and many individuals appear to shed HSV-1 more than 6 times per month. Shedding of HSV-1 is present at many intraoral sites, for brief periods, at copy numbers sufficient to be transmitted, and even in seronegative individuals. The dental implications of these findings are discussed.
Topics: Age Factors; DNA, Viral; Humans; Mouth; Saliva; Simplexvirus; Time Factors; Virus Shedding
PubMed: 17703961
DOI: 10.1016/j.tripleo.2007.06.011 -
International Journal of Infectious... Apr 2021The epidemiological importance of asymptomatic individuals who would never develop illness, compared to those who eventually develop symptoms, has yet to be fully...
BACKGROUND
The epidemiological importance of asymptomatic individuals who would never develop illness, compared to those who eventually develop symptoms, has yet to be fully clarified.
METHODS
The very first cluster data in Tokyo and Kanagawa (n = 36) were analyzed. Movement of all close contact was restricted for 14 days and they underwent laboratory testing with polymerase chain reaction. The reproduction numbers of symptomatic and asymptomatic cases were estimated.
RESULTS
The reproduction number for symptomatic cases was estimated to be 1.2 (95% confidence interval (CI): 0.5-2.9). The relative infectiousness of asymptomatically infected cases was estimated to be 0.27 (95% CI: 0.03-0.81) of symptomatic cases.
CONCLUSION
The relative transmissibility of asymptomatic cases is limited. Observing clusters starting with symptomatic transmission might be sufficient for the control.
Topics: Asymptomatic Infections; Basic Reproduction Number; COVID-19; Female; Humans; Japan; Male; Middle Aged; SARS-CoV-2
PubMed: 33618004
DOI: 10.1016/j.ijid.2021.02.065 -
PM & R : the Journal of Injury,... Jun 2024The prevalence of asymptomatic shoulder pathology has been shown to be high on both ultrasound and magnetic resonance imaging (MRI). The most common shoulder pathologies... (Review)
Review
The prevalence of asymptomatic shoulder pathology has been shown to be high on both ultrasound and magnetic resonance imaging (MRI). The most common shoulder pathologies identified in asymptomatic, non-athlete individuals include rotator cuff pathology, acromioclavicular (AC) joint pathology, labral tears, subacromial bursitis, and calcific tendinitis. The data in the current literature suggest that asymptomatic rotator cuff tears are diagnosed on ultrasound and MRI at high rates, suggesting that rotator cuff tears may be considered an age-related, normal, degenerative change. However, there are data to suggest that the presence of an asymptomatic rotator cuff tear on imaging may predispose a patient to shoulder pain in the future, although the data remain inconclusive. AC joint arthritic changes are also common in older individuals on advanced imaging. Recent studies have reported that labral tears are common in asymptomatic shoulders, although at less frequent rates than in athletes, but more research is required on this topic. In addition, the presence of subacromial bursitis on imaging has not been found to accurately differentiate between symptomatic and asymptomatic shoulders. Finally, calcific tendinitis has been diagnosed asymptomatically, with most individuals remaining asymptomatic. Individuals who did develop pain developed severe pain, although the risk factors for developing symptomatic calcific tendinitis are unclear. In summary, given the high prevalence of shoulder pathology diagnosed on imaging, it is important to not over diagnose or complete an unnecessary workup for an asymptomatic person who is otherwise healthy.
PubMed: 38822702
DOI: 10.1002/pmrj.13169