Relative Importance Of Different Routes Research Articles

Social and environmental transmission spread different sets of gut microbes in wild mice

Gut microbes shape many aspects of organismal biology, yet how these key bacteria transmit among hosts in natural populations remains poorly understood. Recent work in mammals has emphasized either transmission through social contacts or indirect transmission through environmental contact, but the relative importance of different routes has not been directly assessed. Here we used a novel radio-frequency identification-based tracking system to collect long-term high-resolution data on social relationships, space use and microhabitat in a wild population of mice (Apodemus sylvaticus), while regularly characterizing their gut microbiota with 16S ribosomal RNA profiling. Through probabilistic modelling of the resulting data, we identify positive and statistically distinct signals of social and environmental transmission, captured by social networks and overlap in home ranges, respectively. Strikingly, microorganisms with distinct biological attributes drove these different transmission signals. While the social network effect on microbiota was driven by anaerobic bacteria, the effect of shared space was most influenced by aerotolerant spore-forming bacteria. These findings support the prediction that social contact is important for the transfer of microorganisms with low oxygen tolerance, while those that can tolerate oxygen or form spores may be able to transmit indirectly through the environment. Overall, these results suggest social and environmental transmission routes can spread biologically distinct members of the mammalian gut microbiota.

Impact of respiratory aerosol size and number distribution on the relative importance of different routes in SARS-CoV-2 transmission.

Exploring the relative importance of different routes in SARS-CoV-2 transmission is crucial in infection prevention. However, even in the same environmental setting, the relative importance of different routes has varied in different studies. We hypothesize that respiratory aerosol size and number distribution might play a key role. In this study, size and number distribution of respiratory droplets emitted from breathing, talking, and coughing were identified from PubMed and Web of Science. The infection risk of SARS-CoV-2 via airborne, droplet, and fomite transmission routes was modeled in a household and a healthcare setting. The relative importance of three routes varied with different size distributions in both settings. Generally, the contribution of the airborne route increased with the volume percentage of respirable droplets emitted. And the increase of the total number of emitted droplets leads to an increase in the contribution of tdroplet route. In the healthcare setting, as the total number of emitted droplets increased from 110 to 4,973, the contribution of droplet route increased from 62.24% to 98.11%. Next, by considering the combination of breathing, coughing, and talking when the infected person was asymptomatic, the airborne route predominated over the droplet and contact routes. When the infected person had developed symptoms, that is, cough, the droplet route played a dominant role in SARS-CoV-2 transmission. In conclusion, risk analyses will be improved with improved sampling methods that enable characterization of viruses within respiratory droplets of different sizes.

Expert elicitation on the relative importance of possible SARS-CoV-2 transmission routes and the effectiveness of mitigations

ObjectivesTo help people make decisions about the most effective mitigation measures against SARS-CoV-2 transmission in different scenarios, the likelihoods of transmission by different routes need to be quantified to some...

Toward Improving Interventions Against Toxoplasmosis by Identifying Routes of Transmission Using Sporozoite-specific Serological Tools.

BackgroundHorizontal transmission of Toxoplasma gondii occurs primarily via ingestion of environmental oocysts or consumption of undercooked/raw meat containing cyst-stage bradyzoites. The relative importance of these 2 transmission routes remains unclear. Oocyst infection can be distinguished from bradyzoite infection by identification of immunoglobulin G (IgG) antibodies against T. gondii embryogenesis-related protein (TgERP). These antibodies are, however, thought to persist for only 6–8 months in human sera, limiting the use of TgERP serology to only those patients recently exposed to T. gondii. Yet recent serological survey data indicate a more sustained persistence of anti-TgERP antibodies. Elucidating the duration of anti-TgERP IgG will help to determine whether TgERP serology has epidemiological utility for quantifying the relative importance of different routes of T. gondii transmission.MethodsWe developed a serocatalytic mathematical model to capture the change in seroprevalence of non-stage-specific IgG and anti-TgERP IgG antibodies with human age. The model was fitted to published datasets collected in an endemic region of Brazil to estimate the duration of anti-TgERP IgG antibodies, accounting for variable age–force of infection profiles and uncertainty in the diagnostic performance of TgERP serology.ResultsWe found that anti-TgERP IgG persists for substantially longer than previously recognized, with estimates ranging from 8.3 to 41.1 years. The Brazilian datasets were consistent with oocysts being the predominant transmission route in these settings.ConclusionsThe longer than previously recognized duration of anti-TgERP antibodies indicates that anti-TgERP serology could be a useful tool for delineating T. gondii transmission routes in human populations. TgERP serology may therefore be an important epidemiological tool for informing the design of tailored, setting-specific public health information campaigns and interventions.

Assessing metal exposures in a community near a cement plant in the Northeast U.S.

Cement production is a major source of metals and metalloids in the environment, while exposures to metals and metalloids may impact human health in the surrounding communities. We recruited 185 participants living in the vicinity of a cement plant in the northeast U.S., and measured the levels of aluminum (Al), arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), and selenium (Se) in blood and Hg in hair samples from them. A questionnaire was used to assess potential sources of Hg exposure. Multivariate regressions and spatial analyses were performed to evaluate the relative importance of different routes of exposures. The metal concentrations in blood or hair samples of our study participants were comparable to the U.S. general or regional population. Smoking contributed significantly to Cd and Pb exposures, and seafood consumption contributed significantly to Hg and As exposures, while variables related to the cement plant were not significantly associated with metal concentrations. Our results suggest that our study population was not at elevated health risk due to metal exposures, and that the contribution of the cement plant to metal exposures in the surrounding community was minimal.

Detection of infectious disease outbreaks in twenty-two fragile states, 2000-2010: a systematic review.

Fragile states are home to a sixth of the world's population, and their populations are particularly vulnerable to infectious disease outbreaks. Timely surveillance and control are essential to minimise the impact of these outbreaks, but little evidence is published about the effectiveness of existing surveillance systems. We did a systematic review of the circumstances (mode) of detection of outbreaks occurring in 22 fragile states in the decade 2000-2010 (i.e. all states consistently meeting fragility criteria during the timeframe of the review), as well as time lags from onset to detection of these outbreaks, and from detection to further events in their timeline. The aim of this review was to enhance the evidence base for implementing infectious disease surveillance in these complex, resource-constrained settings, and to assess the relative importance of different routes whereby outbreak detection occurs.We identified 61 reports concerning 38 outbreaks. Twenty of these were detected by existing surveillance systems, but 10 detections occurred following formal notifications by participating health facilities rather than data analysis. A further 15 outbreaks were detected by informal notifications, including rumours.There were long delays from onset to detection (median 29 days) and from detection to further events (investigation, confirmation, declaration, control). Existing surveillance systems yielded the shortest detection delays when linked to reduced barriers to health care and frequent analysis and reporting of incidence data.Epidemic surveillance and control appear to be insufficiently timely in fragile states, and need to be strengthened. Greater reliance on formal and informal notifications is warranted. Outbreak reports should be more standardised and enable monitoring of surveillance systems' effectiveness.

Melioidosis: a clinical overview

Melioidosis, an infection caused by the environmental Gram-negative bacillus Burkholderia pseudomallei, has emerged as an important cause of morbidity and mortality in Southeast Asia and northern Australia. a review of the literature using PubMed. Approaches to diagnosis and antimicrobial therapy. Whether seroconversion signals the presence of a quiescent bacterial focus and an increase in long-term risk of melioidosis. Melioidosis is potentially preventable, but there is a striking lack of evidence on which to base an effective prevention programme. An accurate map defining the global distribution of B. pseudomallei is needed, together with studies on the relative importance of different routes of infection. There is a marked difference in mortality from melioidosis in high-income versus lower income countries, and affordable strategies that reduce death from severe sepsis (from any cause) in resource-restricted settings are needed.

Measurements of airborne influenza virus in aerosol particles from human coughs.

Influenza is thought to be communicated from person to person by multiple pathways. However, the relative importance of different routes of influenza transmission is unclear. To better understand the potential for the airborne spread of influenza, we measured the amount and size of aerosol particles containing influenza virus that were produced by coughing. Subjects were recruited from patients presenting at a student health clinic with influenza-like symptoms. Nasopharyngeal swabs were collected from the volunteers and they were asked to cough three times into a spirometer. After each cough, the cough-generated aerosol was collected using a NIOSH two-stage bioaerosol cyclone sampler or an SKC BioSampler. The amount of influenza viral RNA contained in the samplers was analyzed using quantitative real-time reverse-transcription PCR (qPCR) targeting the matrix gene M1. For half of the subjects, viral plaque assays were performed on the nasopharyngeal swabs and cough aerosol samples to determine if viable virus was present. Fifty-eight subjects were tested, of whom 47 were positive for influenza virus by qPCR. Influenza viral RNA was detected in coughs from 38 of these subjects (81%). Thirty-five percent of the influenza RNA was contained in particles >4 µm in aerodynamic diameter, while 23% was in particles 1 to 4 µm and 42% in particles <1 µm. Viable influenza virus was detected in the cough aerosols from 2 of 21 subjects with influenza. These results show that coughing by influenza patients emits aerosol particles containing influenza virus and that much of the viral RNA is contained within particles in the respirable size range. The results support the idea that the airborne route may be a pathway for influenza transmission, especially in the immediate vicinity of an influenza patient. Further research is needed on the viability of airborne influenza viruses and the risk of transmission.

Virus shedding and environmental deposition of novel A (H1N1) pandemic influenza virus: interim findings

Background The relative importance of different routes of influenza transmission, including the role of bioaerosols, and ability of masks and/or hand hygiene to prevent transmission, remains poorly understood. Current evidence suggests that infectious virus is not typically released from adults after 5 days of illness, however, little is known about the extent to which virus is deposited by infected individuals into the environment and whether deposited virus has the ability to infect new hosts. Further information about the deposition of viable influenza virus in the immediate vicinity of patients with pandemic influenza is fundamental to our understanding of the routes and mechanisms of transmission. Objectives To collect data on patients infected with pandemic H1N1 2009 (swine flu). Primary objectives were to correlate the amount of virus detected in a patient’s nose with that recovered from his/her immediate environment, and with symptom duration and severity. Secondary objectives were to describe virus shedding and duration according to major patient characteristics: adults versus children, and those with mild illness (community patients) versus those with more severe disease (hospitalised patients). Methods Adults and children, both in hospital and from the community, who had symptoms of pandemic H1N1 infection, were enrolled and visited every day during follow-up for a maximum of 12 days. Symptom data was collected and samples were taken, including nose swabs and swabs from surfaces and objects around patients. Samples of air were obtained using validated sampling equipment. The samples were tested for the presence of pandemic H1N1 virus, using polymerase chain reaction (PCR) to detect virus genome and an immunofluorescence technique to detect viable virus. Results Forty-three subjects were followed up, and 19 of them were subsequently proven to be infected with pandemic H1N1 virus. The median duration of virus shedding from the 19 infected cases was 6 days when detection was performed by PCR, and 3 days when detection was performed by a culture technique. Over 30% of cases remained potentially infectious for at least 5 days. Only 0.5% of all community and none of the hospital swabs taken revealed virus on surfaces. Five subjects had samples of the air around them collected and virus was detected by PCR from four; some of the air particles in which virus was detected were small enough to be inhaled and deposited deep in the lungs. Limitation Small number of subjects recruited. Conclusions The finding that over 30% of infected individuals have infectious virus in their noses for 5 days or more has infection control implications. The data suggest that contact transmission of pandemic influenza via fomites may be less important than previously thought, but transmission via bioaerosols at short range may be possible, meaning that high-level personal protective equipment may be needed by health-care workers when attending patients with pandemic influenza. Further work is being undertaken to consolidate these findings, as they have important potential implications for the protection of health-care workers and the formulation of advice to households, nationally and internationally.

Modeling Aggregate Exposures to Glycol Ethers from Use of Commercial Floor Products

Computer modeling of aggregate exposure provides the capability to estimate the range of doses that can occur from product use and to understand the relative importance of different routes of exposure. This paper presents an assessment of aggregate occupational exposure to two glycol ethers used as solvents in floor maintenance products for industrial and institutional facilities, using a simulation tool named PROMISE. Three commercial floor-care products were assumed to be applied in sequence--a floor stripper, then a floor cleaner, and lastly a protective coating. The glycol ethers modeled were ethylene glycol butyl ether (EGBE) in the floor stripper and in the floor cleaner, and dipropylene glycol methyl ether (DPGME) in the coating. Modeling uncertainty was assessed through a comparison of the PROMISE inhalation exposure estimates with those from an independent model (MCCEM), and parameter uncertainty was investigated using PROMISE software's Monte Carlo simulation capabilities. Modeling results indicated that inhalation is the dominant exposure route. The predicted average air concentration and inhalation dose from PROMISE agreed with the second model (MCCEM) within 10%. Monte Carlo simulation indicated that the upper end of the aggregate-dose distribution for the scenario was more than 50% higher than the value of the point estimate. The modeled 8-h TWA concentrations for EGBE and DPGME were lower than the corresponding permissible exposure limits American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLV) by at least a factor of 20, indicating that under the assumed conditions workplace exposures to glycol ethers are below levels of concern.

Temperature influences on the accumulation and elimination of mercury in a freshwater cladoceran, Daphnia magna

Temperature is an important environmental variable affecting the physiology and metabolism of aquatic invertebrates and can potentially affect the rate and pathway of the uptake and elimination of contaminants. In this study, we studied the effects of the ambient temperature on the uptake (from water and food) and elimination of inorganic mercury [Hg(II)] and methymercury (MeHg) in a freshwater cladoceran, Daphnia magna, in the laboratory. At different temperatures (i.e., 14, 19 and 24 °C), the assimilation efficiencies of both Hg species from ingested alga were not significantly different while the dissolved uptake rates were 32 and 73% lower at 14 °C than at 24 °C for Hg(II) and MeHg, respectively. The reduced uptake rates of Hg(II) at 14 °C could be adequately explained by the reduced filtration rate (40% reduction), but for MeHg, the reduced filtration rate could not completely explain reduction in MeHg uptake rate. Despite the elimination rates of both Hg compounds not being affected by the temperature, the relative importance of different routes of Hg loss (i.e., excretion, egestion, molting and reproduction) was significantly different at various temperatures. The relative importance of excretion to MeHg loss increased from 24 to 14 °C (i.e., 52 to 85% of Hg loss) while that of reproduction to MeHg loss decreased from 43 to 11% simultaneously. Using a kinetic model, we showed that the fraction of MeHg accumulated in the daphnids coming from the dietary phase was higher at lower temperature, while there was increased accumulation of both Hg(II) and MeHg in the daphnids at higher temperatures. Nevertheless, the trophic transfer potentials for both Hg species in this algae–daphnids food chain were not influenced by the temperature.

On the relative importance of different routes forming NO in hydrogen flames

The objective of the present work was to analyse the relative importance of the different routes forming NO in premixed hydrogen flames by comparing experiments on the combustion of lean mixtures of hydrogen, oxygen and nitrogen with modeling, employing sensitivity analysis

Pathogenesis of BSE.

Before the emergence of bovine spongiform encephalopathy (BSE) and recognition of its zoonotic potential, the major example of the transmissible spongiform encephalopathies (TSEs) of animals was scrapie of sheep. But there is no evidence that scrapie transmits naturally to any species other than sheep and goats. The pathogenesis of scrapie has been studied most in experimental laboratory rodent species. In most experimental models of scrapie, after peripheral non-neural routes of infection, replication of the agent can first be detected in lymphoreticular system (LRS) tissue. When the route of introduction of agent into the body is localized, initial involvement will be in LRS tissue draining the infection site. Thereafter, there is a striking amplification of the agent in the LRS and spread by lymphatic/haematogenous routes, giving widespread dissemination in the LRS. This precedes replication in the CNS, but is not the means by which infection reaches the CNS. There is now substantial evidence from experimental models of scrapie that involvement of the CNS is by peripheral nervous system (PNS) pathways. In some models employing oral exposure the earliest localized LRS replication is in the gut-associated lymphoid tissue (GALT) and autonomic PNS routing to the CNS has been implicated. However, the relative importance of different routes of spread of TSEs within the body is determined by a number of host- and agent-dependent factors and, therefore, generalizations from an experimental model to a natural disease across a species barrier may not be appropriate. With the occurrence of BSE and recognition of its food-borne route of transmission via meat and bone meal, has come greater awareness of the probable importance of the oral route of infection in ruminant species affected by TSEs. In consequence, studies have increasingly focused on the natural host species to examine pathogenetic events.

Ecological Significance of Endocrine Disruption in Marine Invertebrates

Anthropogenic chemicals which can disrupt the hormonal (endocrine) systems of wildlife species are currently a major cause for concern. Reproductive hormone-receptor systems appear to be especially vulnerable. In the past few years, numerous effects of endocrine disrupting chemicals on wildlife have emerged including changes in the sex of riverine fish, reproductive failure in birds and abnormalities in the reproductive organs of alligators and polar bears. Much less is known regarding endocrine disruption in marine invertebrates, the key structural and functional components of marine ecosystems. In this paper, potential effects of different classes of endocrine disrupting chemicals are reviewed. The endocrinology of several major invertebrate groups is briefly examined to identify which phyla are most likely to be at risk. Gaps in our knowledge concerning the availability and uptake of endocrine disruptors are identified. For example, the relative importance of different routes of chemical uptake (from seawater vs food) is considered. Feeding strategies (herbivores, carnivores, deposit feeders, suspension feeders) in relation to uptake of endocrine disruptors are also discussed. Examples of endocrine disruption in marine invertebrates in situ are provided, including imposex in gastropod molluscs exposed to organotin compounds and intersex in crustaceans exposed to sewage discharges. Laboratory data are presented concerning the effects of endocrine disruptors on the growth and reproductive output of the deposit feeding amphipod Corophium volutator and the polychaete worm Dinophilus gyrociliatus. Recent findings are reported which demonstrate reductions in settlement following exposure of barnacle larvae to the xeno-estrogen, 4 nonyl phenol. The potential use of cyprid major protein as a biomarker of oestrogenicity is explored. The ecological significance of endocrine disruption in marine invertebrates is discussed. With regard to environmental management action, an evidence-based approach is advocated. A protocol for collecting evidence of ecologically significant endocrine disruption is outlined.

Ecophysiology of Trace Metal Uptake in Crustaceans

The uptake of trace metals from solution by crustaceans is often described as typically following one of two routes; one passive, the other depending on active transport. In the case of passive facilitated diffusion, the trace metal binds initially to a metal-binding protein in the membrane of the epithelial surface, and then passes down a thermodynamic gradient of metal-binding ligands of increasing metal affinities. Some trace metals may also follow routes for the uptake of major metal ions, as in the case of cadmium and calcium. This uptake is ultimately driven by an energy-requiring pump in the epithelial cell membrane. This may be apical and directly transfer the metal ion into the cell, or as in the case of sodium, a basal ATPase setting up a concentration gradient from the medium to the interior of the cell allowing entry down a metal-transporting channel. Carrier proteins and channels may indeed be variations of the same theme. The relative importance of different routes varies between trace metals and between crustaceans, often according to their ecology. The physicochemistry of trace metal speciation in solution is important in releasing the free metal ion, typically the bioavailable form of a trace metal, but the physiological responses of particular crustaceans may interact to affect uptake rates. Such physiological responses include changes in activities of major ion pumps and integumental permeability, and appear to be a feature of common, but physiologically special, euryhaline crustaceans.

Maternal prevalence of Toxoplasma antibody based on anonymous neonatal serosurvey: a geographical analysis.

A total of 12,902 neonatal samples collected on absorbent paper for routine metabolic screening were tested anonymously for antibodies to toxoplasma. Seroprevalence varied from 19.5% in inner London, to 11.6% in suburban London, and 7.6% in non-metropolitan districts. Much of this variation appeared to be associated with the proportions of livebirths in each district to women born outside the UK. However, additional geographical variation remained and seroprevalence in UK-born women was estimated to be 12.7% in inner London, 7.5% in suburban London, and 5.5% in non-metropolitan areas. These estimates are considerably lower than any previously reported in antenatal sera in the UK. The wide geographical variation highlights a need for further research to determine the relative importance of different routes of transmission.

Quantitation of arsenic species in urine for exposure assessment studies

Accuracy in trace level clinical or biomedical analyses is of increasing importance as populationbased surveillance is more widely used to address issues of nutritional requirements, environmental exposures, and epidemiological outcomes. Among the uses of such surveillance, evaluation of community exposures from a local arsenic pollution source is one example. Urinary biological monitoring is a desirable tool used in conjunction with measurement of environmental levels of arsenic in order to permit assessment of total exposures and to provide a basis for consideration of the relative importance of different routes of exposure and of age-related behaviors in influencing exposure. Urinary arsenic concentrations are indicative of recent (previous 1-2 days) exposures to arsenic. When total urinary arsenic is measured, total arsenic intake is assessed. When exposures to inorganic arsenic (in the forms of oxides or salts of trivalent or pentavalent arsenic) are of interest, determination of urinary arsenic species comprising the major metabolites of inorganic arsenic exposures is most appropriate [1]. A recent two-year study of community exposures to environmental inorganic arsenic pollution utilized urinary arsenic speciation analysis to assess exposures. In these analyses, part-per-billion sensitivity was achieved with a mean precision of less than 12% coefficient of variation, and with excellent interlaboratory comparability.