For many infectious disease processes such as emerging zoonoses and vaccine-preventable diseases, 0< R.sub.0 <1 and infections occur as self-limited stuttering transmission chains. A mechanistic ...understanding of transmission is essential for characterizing the risk of emerging diseases and monitoring spatio-temporal dynamics. Thus methods for inferring R.sub.0 and the degree of heterogeneity in transmission from stuttering chain data have important applications in disease surveillance and management. Previous researchers have used chain size distributions to infer R.sub.0, but estimation of the degree of individual-level variation in infectiousness (as quantified by the dispersion parameter, k) has typically required contact tracing data. Utilizing branching process theory along with a negative binomial offspring distribution, we demonstrate how maximum likelihood estimation can be applied to chain size data to infer both R.sub.0 and the dispersion parameter that characterizes heterogeneity. While the maximum likelihood value for R.sub.0 is a simple function of the average chain size, the associated confidence intervals are dependent on the inferred degree of transmission heterogeneity. As demonstrated for monkeypox data from the Democratic Republic of Congo, this impacts when a statistically significant change in R.sub.0 is detectable. In addition, by allowing for superspreading events, inference of k shifts the threshold above which a transmission chain should be considered anomalously large for a given value of R.sub.0 (thus reducing the probability of false alarms about pathogen adaptation). Our analysis of monkeypox also clarifies the various ways that imperfect observation can impact inference of transmission parameters, and highlights the need to quantitatively evaluate whether observation is likely to significantly bias results.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
Background
Progress towards elimination of trachoma as a public health problem has been substantial, but the coronavirus disease 2019 (COVID-19) pandemic has disrupted community-based ...control efforts.
Methods
We use a susceptible-infected model to estimate the impact of delayed distribution of azithromycin treatment on the prevalence of active trachoma.
Results
We identify three distinct scenarios for geographic districts depending on whether the basic reproduction number and the treatment-associated reproduction number are above or below a value of 1. We find that when the basic reproduction number is <1, no significant delays in disease control will be caused. However, when the basic reproduction number is >1, significant delays can occur. In most districts, 1 y of COVID-related delay can be mitigated by a single extra round of mass drug administration. However, supercritical districts require a new paradigm of infection control because the current strategies will not eliminate disease.
Conclusions
If the pandemic can motivate judicious, community-specific implementation of control strategies, global elimination of trachoma as a public health problem could be accelerated.
Abstract
Background
Methicillin-resistant staphylococcus aureus (MRSA) colonization of hospitalized patients is associated with higher readmission rates and increased morbidity. Depending on the ...mechanisms of transmission, numerous potential control interventions exist to reduce the burden of disease. However, given the preponderance of asymptomatic colonization, it is challenging to quantify the relative importance of different transmission mechanisms and assess control efficacy. By identifying clusters of transmission, whole-genome sequencing (WGS) provides an opportunity to overcome these challenges.
Methods
We sought to apply cluster analysis techniques to WGS data for MRSA, in order to assess MRSA prevalence, transmissibility, the degree of transmission heterogeneity and the potential effectiveness of control. Our model builds upon previous work that showed a direct relationship between the size distribution of infection clusters, the effective reproduction number (R) and the dispersion parameter (k). To demonstrate its functionality, our model was applied to existing WGS data for MRSA isolates collected during a 12 month period in the East of England (DOI: 10.1126/scitranslmed.aak9745)
Results
The effective reproduction number for the East of England data is 0.29 (95% CI: 0.24–0.36). The dispersion parameter is 0.09 (0.03–0.33) reflecting a high degree of transmission heterogeneity. This implies all transmission is caused by just 12% of the cases. Targeted control of these cases could have decreased overall burden of MRSA colonization by 29% during the time period of the study.
Conclusion
The high degree of transmission heterogeneity seen in MRSA transmission suggests that the risk for infection is variable.This observation motivates the need for more detailed mechanistic modeling of hospital-based MRSA transmission that integrates patients-specific factors, movement data and genome sequencing. Such models could be used to forecast which patients are at greatest risk for either acquiring or transmitting MRSA, thereby improving targeted control.
Disclosures
All authors: No reported disclosures.
Abstract
Background
Tremendous progress towards elimination of trachoma as a public health problem has been made. However, there are areas where the clinical indicator of disease, trachomatous ...inflammation—follicular (TF), remains prevalent. We quantify the progress that has been made, and forecast how TF prevalence will evolve with current interventions. We also determine the probability that a district is a transmission-hotspot based on its TF prevalence (ie, reproduction number greater than one).
Methods
Data on trachoma prevalence come from the GET2020 global repository organized by the World Health Organization and the International Trachoma Initiative. Forecasts of TF prevalence and the percent of districts with local control is achieved by regressing the coefficients of a fitted exponential distribution for the year-by-year distribution of TF prevalence. The probability of a district being a transmission-hotspot is extrapolated from the residuals of the regression.
Results
Forecasts suggest that with current interventions, 96.5% of surveyed districts will have TF prevalence among children aged 1–9 years <5% by 2030 (95% CI: 86.6%–100.0%). Districts with TF prevalence < 20% appear unlikely to be transmission-hotspots. However, a district having TF prevalence of over 28% in 2016–2019 corresponds to at least 50% probability of being a transmission-hotspot.
Conclusions
Sustainable control of trachoma appears achievable. However there are transmission-hotspots that are not responding to annual mass drug administration of azithromycin and require enhanced treatment in order to reach local control.
Our ability to respond appropriately to infectious diseases is enhanced by identifying differences in the potential for transmitting infection between individuals. Here, we identify epidemiological ...traits of self-limited infections (i.e. infections with an effective reproduction number satisfying ) that correlate with transmissibility. Our analysis is based on a branching process model that permits statistical comparison of both the strength and heterogeneity of transmission for two distinct types of cases. Our approach provides insight into a variety of scenarios, including the transmission of Middle East Respiratory Syndrome Coronavirus (MERS-CoV) in the Arabian peninsula, measles in North America, pre-eradication smallpox in Europe, and human monkeypox in the Democratic Republic of the Congo. When applied to chain size data for MERS-CoV transmission before 2014, our method indicates that despite an apparent trend towards improved control, there is not enough statistical evidence to indicate that has declined with time. Meanwhile, chain size data for measles in the United States and Canada reveal statistically significant geographic variation in , suggesting that the timing and coverage of national vaccination programs, as well as contact tracing procedures, may shape the size distribution of observed infection clusters. Infection source data for smallpox suggests that primary cases transmitted more than secondary cases, and provides a quantitative assessment of the effectiveness of control interventions. Human monkeypox, on the other hand, does not show evidence of differential transmission between animals in contact with humans, primary cases, or secondary cases, which assuages the concern that social mixing can amplify transmission by secondary cases. Lastly, we evaluate surveillance requirements for detecting a change in the human-to-human transmission of monkeypox since the cessation of cross-protective smallpox vaccination. Our studies lay the foundation for future investigations regarding how infection source, vaccination status or other putative transmissibility traits may affect self-limited transmission.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Our understanding of the different effects of targeted versus nontargeted violence on Ebola virus (EBOV) transmission in Democratic Republic of the Congo (DRC) is limited.
We used time-series data of ...case counts to compare individuals in Ebola-affected health zones in DRC, April 2018-August 2019. Exposure was number of violent events per health zone, categorized into Ebola-targeted or Ebola-untargeted, and into civilian-induced, (para)military/political, or protests. Outcome was estimated daily reproduction number (Rt) by health zone. We fit linear time-series regression to model the relationship.
Average Rt was 1.06 (95% confidence interval CI, 1.02-1.11). A mean of 2.92 violent events resulted in cumulative absolute increase in Rt of 0.10 (95% CI, .05-.15). More violent events increased EBOV transmission (P = .03). Considering violent events in the 95th percentile over a 21-day interval and its relative impact on Rt, Ebola-targeted events corresponded to Rt of 1.52 (95% CI, 1.30-1.74), while civilian-induced events corresponded to Rt of 1.43 (95% CI, 1.21-1.35). Untargeted events corresponded to Rt of 1.18 (95% CI, 1.02-1.35); among these, militia/political or ville morte events increased transmission.
Ebola-targeted violence, primarily driven by civilian-induced events, had the largest impact on EBOV transmission.
The continued elimination of measles requires accurate assessment of its epidemiology and a critical evaluation of how its incidence is changing with time. National surveillance of measles in the ...United States between 2001 and 2011 provides data on the number of measles introductions and the size of the resulting transmission chains. These data allow inference of the effective reproduction number, Reff, and the probability of an outbreak occurring. Our estimate of 0.52 (95% confidence interval: 0.44, 0.60) for Reff is smaller than prior results. Our findings are relatively insensitive to the possibility that as few as 75% of cases were detected. Although we confirm that measles remains eliminated, we identify an increasing trend in the number of measles cases with time. We show that this trend is likely attributable to an increase in the number of disease introductions rather than a change in the transmissibility of measles. However, we find that transmissibility may increase substantially if vaccine coverage drops by as little as 1%. Our general approach of characterizing the case burden of measles is applicable to the epidemiologic assessment of other weakly transmitting or vaccine-controlled pathogens that are either at risk of emerging or on the brink of elimination.
In line with movement restrictions and physical distancing essential for the control of the COVID-19 pandemic, WHO recommended postponement of all neglected tropical disease (NTD) control activities ...that involve community-based surveys, active case finding, and mass drug administration in April, 2020. Following revised guidance later in 2020, and after interruptions to NTD programmes of varying lengths, NTD programmes gradually restarted in the context of an ongoing pandemic. However, ongoing challenges and service gaps have been reported. This study aimed to evaluate the potential effect of the programmatic interruptions and strategies to mitigate this effect.
For seven NTDs, namely soil-transmitted helminths, schistosomiasis, lymphatic filariasis, onchocerciasis, trachoma, visceral leishmaniasis, and human African trypanosomiasis, we used mathematical transmission models to simulate the effect of programme interruptions on the dynamics of each of these diseases in different endemic settings. We also explored the potential benefit of implementing mitigation strategies, primarily in terms of minimising the delays to control targets.
We show that the effect of the COVID-19-induced interruption in terms of delay to achieving elimination goals might in some cases be much longer than the duration of the interruption. For schistosomiasis, onchocerciasis, trachoma, and visceral leishmaniasis, a mean delay of 2–3 years for a 1-year interruption is predicted in areas of highest prevalence. We also show that these delays can largely be mitigated by measures such as additional mass drug administration or enhanced case-finding.
The COVID-19 pandemic has brought infectious disease control to the forefront of global consciousness. It is essential that the NTDs, so long neglected in terms of research and financial support, are not overlooked, and remain a priority in health service planning and funding.
Bill & Melinda Gates Foundation, Medical Research Council, and the UK Foreign, Commonwealth & Development Office.
Investigate risk factors for unplanned return to the operating room after resident-performed cataract surgery.
Retrospective case-control study.
Institutional.
Study population: All patients with ...reoperation within 90 days of resident-performed phacoemulsification were matched to four control eyes which had surgery within 30 days of the reoperation at the same institution.
Billing codes were used to identify all patients who underwent resident-performed intended phacoemulsification with intraocular lens placement from January 2005 to December 2010.
Investigated risk factors for reoperation included cataract characteristics and preexisting ocular co-morbidities, including diabetic retinopathy, retinal detachment history, glaucoma, corneal pathology, and uveitis. Additional preoperative risk factors studied included resident training year, history of tamsulosin use, phacodonesis, pupillary dilation, presence of pseudoexfoliation, myopia, history of trauma, visual acuity, and monocular status. Intraoperative variables were the use of iris expansion devices, use of capsular stain, attending type, incision type, use of sutures, vitreous loss, anesthesia type, and phacoemulsification technique.
There were 67 returns to the operating room (i.e., cases) over five years that were assigned to 268 control eyes. In preoperative multivariate analysis, phacoemulsification done by a first- or second-year resident (OR 3.2, 95% CI: 1.7-6.0, p < 0.001) was associated with an increased risk of reoperation. In postoperative multivariate analysis, only the use of the divide-and-conquer technique (OR 4.0, 95% CI:1.7-9.2, p = 0.001) was associated with an increased risk of reoperation.
Phacoemulsification done by a junior resident or using the divide-and-conquer technique had the highest risk of reoperation.
Friends often help each other without direct compensation. This behavior seems to contravene a basic tenet of economics, that prices and payment help coordinate supply and demand, increasing welfare. ...If compensation is useful between strangers, why not between friends as well?I address this question by building a model of bilateral trade in a friendship, where the price must be specified ex ante, and use it to understand under which circumstances a price of zero is an equilibrium outcome. In the model, two people have altruistic preferences towards each other, but may also have incomplete information about each other's motives. While altruists are able to undertake some beneficial transactions even at a price of zero, they would still benefit from a more efficient price. In contrast to previous work, I find that choosing to forgo payment cannot arise from being altruistic, nor from wanting to signal one's altruism. The key driver of this result is that the benefit of an altruistic reputation is greater to a selfish person than to an altruistic one, so no separating equilibrium in a signaling game could be sustained in which only the altruistic type sets price to zero.Instead, I find that a separating equilibrium is possible where a price of zero signals a partner’s trust in the other’s altruism, though this result can only be sustained at extreme parameters. Overall, my model rules out altruism signaling as a fundamental reason for the lack of priced transactions between friends, but opens the possibility that this behavior could be driven by signaling of trust. I conclude by discussing alternative approaches to examining this widespread behavior.
![Inference of [R.sub.0] and ...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1553-734X/small "Inference of [R.sub.0] and transmission heterogeneity from the size distribution of stuttering chains")
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