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Virology Journal Nov 2006Widespread deaths of wild birds from which highly pathogenic avian influenza virus H5N1 has been isolated suggest that the virus continues to be lethal to them. However,...
BACKGROUND
Widespread deaths of wild birds from which highly pathogenic avian influenza virus H5N1 has been isolated suggest that the virus continues to be lethal to them. However, asymptomatic carriage by some wild birds could allow birds to spread the virus on migration. Confirmation of such carriage is therefore important for the design of mitigation measures for the disease in poultry.
DISCUSSION
Two recent papers have reported the isolation of H5N1 from a small number of water birds in China and Russia and have concluded that wild birds can spread the viruses over long distances on migration. However, both papers contain weaknesses in the provision of ornithological and associated data that compromise conclusions that can be reached about the role of wild birds in the spread of H5N1. We describe the weaknesses of these studies and highlight the need for improved methodological description and methodology, where appropriate, and further research.
SUMMARY
A rigorous assessment of whether wild birds can carry H5N1 asymptomatically is critical to evaluating the risks of spread by migratory birds on long-distance migration.
Topics: Animal Migration; Animals; Birds; Carrier State; Environmental Monitoring; Influenza A Virus, H5N1 Subtype; Influenza in Birds
PubMed: 17112378
DOI: 10.1186/1743-422X-3-96 -
Mathematical Biosciences Jul 2018What role do asymptomatically infected individuals play in the transmission dynamics? There are many diseases, such as norovirus and influenza, where some infected hosts...
What role do asymptomatically infected individuals play in the transmission dynamics? There are many diseases, such as norovirus and influenza, where some infected hosts show symptoms of the disease while others are asymptomatically infected, i.e. do not show any symptoms. The current paper considers a class of epidemic models following an SEIR (Susceptible → Exposed → Infectious → Recovered) structure that allows for both symptomatic and asymptomatic cases. The following question is addressed: what fraction ρ of those individuals getting infected are infected by symptomatic (asymptomatic) cases? This is a more complicated question than the related question for the beginning of the epidemic: what fraction of the expected number of secondary cases of a typical newly infected individual, i.e. what fraction of the basic reproduction number R, is caused by symptomatic individuals? The latter fraction only depends on the type-specific reproduction numbers, while the former fraction ρ also depends on timing and hence on the probabilistic distributions of latent and infectious periods of the two types (not only their means). Bounds on ρ are derived for the situation where these distributions (and even their means) are unknown. Special attention is given to the class of Markov models and the class of continuous-time Reed-Frost models as two classes of distribution functions for latent and infectious periods. We show how these two classes of models can exhibit very different behaviour.
Topics: Basic Reproduction Number; Caliciviridae Infections; Communicable Diseases; Computer Simulation; Disease Susceptibility; Epidemics; Humans; Influenza, Human; Markov Chains; Mathematical Concepts; Measles; Models, Biological; Stochastic Processes
PubMed: 29654792
DOI: 10.1016/j.mbs.2018.04.002 -
Insects Jul 2018Plant pathogens can profoundly affect host plant quality as perceived by their insect herbivores, with potentially far-reaching implications for the ecology and...
Plant pathogens can profoundly affect host plant quality as perceived by their insect herbivores, with potentially far-reaching implications for the ecology and structure of insect communities. Changes in host plants may have direct effects on the life-histories of their insect herbivores, which can then influence their value as prey to their natural enemies. While there have been many studies that have explored the effects of infection when plants show symptoms of disease, little is understood about how unexpressed infection may affect interactions at higher trophic levels. We examined how systemic, asymptomatic, and seed-borne infection by the ubiquitous plant pathogen , infecting two varieties of the lettuce , affected aphids (the green peach aphid, ) and two widely used biocontrol agents (the parasitoid and the ladybird predator ). Lettuce varieties differed in host plant quality. Asymptomatic infection reduced chlorophyll content and dry weight of host plants, irrespective of plant variety. Aphids reared on asymptomatic plants were smaller, had reduced off-plant survival time and were less fecund than aphids reared on uninfected plants. Parasitoids showed reduced attack rates on asymptomatically infected plants, and wasps emerging from hosts reared on such plants were smaller and showed reduced starvation resistance. When given a choice in an olfactometer, aphids preferentially chose uninfected plants of one variety (Tom Thumb) but showed no preference with the second (Little Gem) variety. Parasitoids preferentially chose aphids on uninfected plants, irrespective of host plant variety, but ladybirds did not show any such preference. These results suggest that the reduced quality of plants asymptomatically infected by negatively affects the life history of aphids and their parasitoids, and alters the behaviors of aphids and parasitoids, but not of ladybirds. Fungal pathogens are ubiquitous in nature, and this work shows that even when host plants are yet to show symptoms, pathogens can affect interactions between insect herbivores and their natural enemies. This is likely to have important implications for the success of biological control programs.
PubMed: 29986404
DOI: 10.3390/insects9030080 -
Infection Control and Hospital... Jan 2022The sensitivity of the BinaxNOW coronavirus disease 2019 (COVID-19) Ag Card test (BinaxNOW) was 51.6% among asymptomatic healthcare employees relative to real-time...
Performance of the BinaxNOW coronavirus disease 2019 (COVID-19) Antigen Card test relative to the severe acute respiratory coronavirus virus 2 (SARS-CoV-2) real-time reverse transcriptase polymerase chain reaction (rRT-PCR) assay among symptomatic and asymptomatic healthcare employees.
The sensitivity of the BinaxNOW coronavirus disease 2019 (COVID-19) Ag Card test (BinaxNOW) was 51.6% among asymptomatic healthcare employees relative to real-time reverse transcriptase polymerase chain reaction (rRT-PCR). The odds of a positive BinaxNOW test decreased as cycle threshold value increased. BinaxNOW could facilitate rapid detection and isolation of asymptomatically infected persons in some settings while rRT-PCR results are pending.
Topics: Antigens, Viral; Asymptomatic Infections; COVID-19; COVID-19 Nucleic Acid Testing; COVID-19 Testing; Health Personnel; Humans; RNA-Directed DNA Polymerase; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; Sensitivity and Specificity
PubMed: 33487197
DOI: 10.1017/ice.2021.20 -
Frontiers in Cellular and Infection... 2019, or Group A Streptococcus (GAS), is a human-restricted pathogen most commonly found in the posterior oropharynx of the human host. The bacterium is responsible for 600... (Review)
Review
, or Group A Streptococcus (GAS), is a human-restricted pathogen most commonly found in the posterior oropharynx of the human host. The bacterium is responsible for 600 million annual cases of pharyngitis globally and has been found to asymptomatically colonize the pharynxes of 4-30% of the population. As such, many studies have utilized animals as models in order to decipher bacterial and host elements that contribute to the bacterial-pharyngeal interaction and determine differences between acute infection and asymptomatic colonization. The aim of this review is to first describe both bacterial and host factors that are important for the pharyngeal persistence of GAS in humans, then to detail the bacterial and host factors that are important for colonization in murine model, and finally to compare the two in order to evaluate the strength of murine pharyngeal colonization as a model for the human-GAS pharyngeal interaction.
Topics: Animals; Carrier State; Disease Models, Animal; Mice; Pharynx; Streptococcal Infections; Streptococcus pyogenes
PubMed: 31119108
DOI: 10.3389/fcimb.2019.00137 -
Journal of Food Protection May 2017Giardia duodenalis is a protozoan that causes a gastrointestinal illness called giardiasis. Giardiasis outbreaks in the United States are most commonly associated with...
Giardia duodenalis is a protozoan that causes a gastrointestinal illness called giardiasis. Giardiasis outbreaks in the United States are most commonly associated with waterborne transmission and are less commonly associated with food, person-to-person, and zoonotic transmission. During June to September 2015, an outbreak of 20 giardiasis cases occurred and were epidemiologically linked to a local grocery store chain on Long Island, New York. Further investigation revealed three asymptomatic food handlers were infected with G. duodenalis, and one food handler and one case were coinfected with Cryptosporidium spp. Although G. duodenalis was not detected in food samples, Cryptosporidium was identified in samples of spinach dip and potato salad. The G. duodenalis assemblage and subtype from one of the food handlers matched two outbreak cases for which genotyping could be performed. This outbreak highlights the potential role of asymptomatically infected food handlers in giardiasis outbreaks.
PubMed: 28402185
DOI: 10.4315/0362-028X.JFP-16-415 -
The Medical Journal of Australia Aug 2021
Topics: COVID-19; Humans; SARS-CoV-2
PubMed: 34287916
DOI: 10.5694/mja2.51174 -
Frontiers in Microbiology 2020is a leading cause for clinical infections and food intoxications, causing over 100,000 yearly cases of bacteremia in the United States and 434 food-borne outbreaks in...
is a leading cause for clinical infections and food intoxications, causing over 100,000 yearly cases of bacteremia in the United States and 434 food-borne outbreaks in the European Union. Approximately 30% of the population permanently carry asymptomatically in their nasal cavity. The risk of infection and transmission to food items or the environment is higher in individuals that are nasally colonized. In addition, can acquire various antimicrobial resistances leading to therapeutic failure, additional medical costs, and fatalities. Methicillin-resistant (MRSA) cause a considerable burden of disease in humans and animals. MRSA carriage has been associated with animal and in particular livestock contact. Extensive current data on the virulence gene profiles, as well as data on antimicrobial resistance determinants is crucial in developing effective strategies to mitigate the burden of disease. To this end, we screened the anterior nares of 160 test subjects (87 pupils and 73 members of farmer families) in Switzerland for carriage. A total of 73 isolates were obtained. Factors such as exposure to farm or companion animals and personal medical history were recorded using a questionnaire. Using a DNA microarray, isolates were assigned to clonal complexes (CCs), and virulence and resistance gene profiles were determined. The collected strains were assigned to 20 CCs, among others CC1, CC7, CC8, CC15, CC30, CC45, CC97, and CC398. Two MRSA strains and one multiresistant isolate carrying genes , , , , and were isolated from farmers with intensive exposure to animals. Strains carrying , causing severe skin lesions and necrotizing pneumonia, as well as tetracycline, erythromycin, and kanamycin resistance genes were found in individuals that had taken antibiotics during the last year. A variety of superantigenic toxin genes was detected, including among others, the toxic shock syndrome toxin (), and various enterotoxins (, , , and the cluster). Contact to chickens was identified as a significant factor contributing to colonization.
PubMed: 32670229
DOI: 10.3389/fmicb.2020.01289 -
Iranian Journal of Medical Sciences Sep 2015Castleman's disease, giant lymph node hyperplasia, is a kind of benign lymphoproliferative disease with gentle behavior. Its etiology and prevalence are unclear. This...
Castleman's disease, giant lymph node hyperplasia, is a kind of benign lymphoproliferative disease with gentle behavior. Its etiology and prevalence are unclear. This rare disease is usually found in mediastinal area asymptomatically and incidentally. It is also rare to see this tumor in the retroperitoneum. In this study, we have introduced a 34-year-old woman who referred just with occasional abdominal pain caused by compressive symptoms. Laboratory findings only reported microcytic anemia (MCH: 18.5, MCV: 63, Hemoglobin 10.2 g/dl). Chest and abdominal X-ray imaging showed no remarkable point. In abdominal ultrasonography, a solid and firm tumor with 12.2×5.3×6.6 cm was reported in patient's retroperitoneum. Patient's surgery was done and the tumor (covered by a fibrous thick capsule, with no bizarre appearance and bleeding) was completely removed. Pathologic examination indicated a Castleman's tumor, type of unicentric and hyaline-vascular. This item had been one of the rare reported items of Castleman's disease in the retroperitoneal space.
PubMed: 26379356
DOI: No ID Found -
International Journal of General... 2021This study aimed to evaluate asymptomatic flexor pollicis longus (FPL) tendon condition after volar plate fixation for distal radius fracture using shear wave...
OBJECTIVE
This study aimed to evaluate asymptomatic flexor pollicis longus (FPL) tendon condition after volar plate fixation for distal radius fracture using shear wave elastography (SWE).
METHODS
We evaluated 36 distal radius fractures with shear wave elastography to evaluate the FPL tendon after volar plate fixation. Ultrasonography was used to measure the FPL distance to the volar plate in the involved wrists, and the thickness of the FPL tendon in the involved wrists was measured on SWE sonograms taken 12 months postoperatively. Measurements of the involved wrists were compared with those of the intact wrists. The radiographic parameters and Soong grade were collected to analyze the correlation between these indicators and the value of the Young's modulus and asymptomatic tendon injury.
RESULTS
The mean values of the Young's modulus for involved wrist were lower than for intact wrist tendons. The values of the Young's modulus were correlated with the FPL distance, radial inclination, and Soong grade. FPL tendons of involved wrists exhibited in the majority a yellow (intermediate) SWE signal, compared to intact wrist tendons, which exhibited a red (hard) signal in the vast majority, and there were significant differences between the involved and intact wrist.
CONCLUSION
FPL tendon may develop asymptomatically changes after volar locking plate fixation of distal radius fractures, which can be detected by SWE effectively. FPL distance, radial accretion, and Soong grade may be the main causes of asymptomatic FPL tendon erosion.
PubMed: 33500654
DOI: 10.2147/IJGM.S290017