06 May 2015

Research Articles of the Week, May 04, 2015

Articles from May_04_2015

Research Committee Selected Articles for the Week of May_04_2015

***-Article is considered for Award Nomination***

When private actors matter: Information-sharing network and surveillance of Highly Pathogenic Avian Influenza in Vietnam

The effectiveness of animal health surveillance systems depends on their capacity to gather sanitary information from the animal production sector. In order to assess this capacity we analyzed the flow of sanitary information regarding Highly Pathogenic Avian Influenza (HPAI) suspicions in poultry in Vietnam. Participatory methods were applied to assess the type of actors and likelihood of information sharing between actors in case of HPAI suspicion in poultry. While the reporting of HPAI suspicions is mandatory, private actors had more access to information than public actors. Actors of the upstream sector (medicine and feed sellers) played a key role in the diffusion of information. The central role of these actors and the influence of the information flow on the adoption by poultry production stakeholders of behaviors limiting (e.g. prevention measures) or promoting disease transmission (e.g. increased animal movements) should be accounted for in the design of surveillance and control programs. © 2015 Elsevier B.V.

Foodborne illness and seasonality related to mobile food sources at festivals and group gatherings in the state of Georgia

Little is known about the relationship of location and season to the pathogen and impact of foodborne illness. A sample of 244 foodborne illness outbreaks from the Foodborne Outbreak Online Database System stemming from festivals (mobile food sources) and group gatherings in Georgia between 1998 and 2010 was examined to determine if season and location were related to pathogen and the number of ill or hospitalized individuals. Results of Chi-square tests of independence, one-way analysis of variance, and the Kruskal-Wallis test showed that norovirus and Salmonella were more strongly associated with group gatherings; Staphylococcus outbreaks were more associated with festivals; norovirus was more frequent during winter; and Salmonella was more associated with summer and autumn events. Location and impact were significant for outbreaks associated with group gatherings, resulting in more hospitalizations than outbreaks associated with festivals. No statistically significant difference occurred between the numbers of reported illnesses stemming from festivals versus group gatherings nor did a seasonal difference occur in the total number of individuals who fell ill or were hospitalized.

Daily forecast of dengue fever incidents for urban villages in a city

Background: Instead of traditional statistical models for large spatial areas and weekly or monthly temporal units, what public health workers urgently need is a timely risk prediction method for small areas. This risk prediction would provide information for early warning, target surveillance and intervention. Methods: Daily dengue cases in the 457 urban villages of Kaohsiung City, Taiwan from 2009 to 2012 were used for model development and evaluation. There were in total 2,997 confirmed dengue cases during this period. A logistic regression model was fitted to the daily incidents occurring in the villages for the past 30 days. The fitted model was then used to predict the incidence probabilities of dengue outbreak for the villages the next day. A percentile of the 457*30 fitted incidence probabilities was chosen to determine a cut-point for issuing the alerts. The covariates included three different levels of spatial effect, and with four lag time periods. The population density and the meteorological conditions were also included for the prediction. Results: The performance of the prediction models was evaluated on 122 consecutive days from September 1 to December 31, 2012. With the 80th percentile threshold, the median sensitivity was 83% and the median false positive rate was 23%. We found that most of the coefficients of the predictors of having cases at the same village in the previous 14 days were positive and significant for the 122 daily updated models. The estimated coefficients of population density were significant during the peak of the epidemic in 2012. Conclusions: The proposed method can provide near real-time dengue risk prediction for a small area. This can serve as a useful decision making tool for front-line public health workers to control dengue epidemics. The precision of the spatial and temporal units can be easily adjusted to different settings for different cities. © 2015 Chan et al.; licensee BioMed Central.

Epidemiology of the foot-and-mouth disease serotype O epidemic of November 2010 to April 2011 in the Republic of Korea

The largest epidemic of foot-and-mouth disease (FMD) in Korea since the first record in 1911 occurred between November 2010 and April 2011. The outbreak was confirmed in 153 farms, and more than three million animals were destroyed. This study presents the temporal and spatial distribution patterns, epidemiological investigation and the control measures for the 2010/2011 epidemic in Korea. The index case of this 2010/2011 FMD epidemic was reported in a pig-farming complex with five piggeries in Andong, GyeongBuk Province, on 28 November 2010, and the outbreak lasted 145 days. The largest number of new detection of the infected farms per day was recorded in mid-January. Epidemiological investigation revealed that the FMD virus had spread from farm to farm through routine movements associated with animal husbandry operations. In contrast to FMD epidemics in other countries in which movement of the infected animals largely contributed to the spread of the disease, human behaviours were major factors in the spread of the FMD virus in the Korean epidemic. The 2010/2011 epidemic was first confirmed in a local small and medium city where share of smallholder producers is higher than that of other provinces. Although Korea had a well-developed emergent response system with the experience of controlling infection and re-obtaining FMD-free status after the previous epidemics, Korea was prompted to revise their contingency plan by tailoring it to its unique livestock environment. Practical contingency plans tailored to Korea for control of FMD can be fully effective when farmers, livestock-related agencies, veterinary service providers and the general public work together. © 2013 Blackwell Verlag GmbH.

Nationwide registry-based ecological analysis of Q fever incidence and pregnancy outcome during an outbreak in the Netherlands

Objective: Whether areas affected by Q fever during a large outbreak (2008-2010) had higher rates of adverse pregnancy outcomes than areas not affected by Q fever. Design: Nationwide registry-based ecological study. Setting: Pregnant women in areas affected and not affected by Q fever in the Netherlands, 2003-2004 and 2008-2010. Participants: Index group (N=58 737): pregnant women in 307 areas with more than two Q fever notifications. Reference group (N=310 635): pregnant women in 921 areas without Q fever notifications. As a baseline, pregnant women in index and reference areas in the years 2003-2004 were also included in the reference group to estimate the effect of Q fever in 2008-2010, and not the already existing differences before the outbreak. Main outcome measures: Preterm delivery, small for gestational age, perinatal mortality. Results: In 2008-2010, there was no association between residing in a Q fever-affected area and both preterm delivery (adjusted OR 1.01 (95% CI 0.94 to 1.08)), and perinatal mortality (adjusted OR 0.87 (95% CI 0.72 to 1.05)). In contrast, we found a weak significant association between residing in a Q fever-affected area in 2008-2010 and small for gestational age (adjusted OR 1.06 (95% CI 1.01 to 1.12)), with a population-attributable fraction of 0.70% (95% CI 0.07% to 1.34%). We observed no dose-response relation for this outcome with increasing Q fever notifications, and we did not find a stronger association for women who were in their first trimester of pregnancy during the months of high human Q fever incidence. Conclusions: This study found a weak association between residing in a Q fever-affected area and the pregnancy outcome small for gestational age. Early detection of infection would require mass screening of pregnant women; this does not seem to be justified considering these results, and the uncertainties about its efficacy and the adverse effects of antibiotic treatment. © 2015, BMJ Publishing Group. All rights reserve

Monitoring of non-cigarette tobacco use using google trends

Background Google Trends is an innovative monitoring system with unique potential to monitor and predict important phenomena that may be occurring at a population level. We sought to validate whether Google Trends can additionally detect regional trends in youth and adult tobacco use. Methods We compared 2011 Google Trends relative search volume data for cigars, cigarillos, little cigars and smokeless tobacco with state prevalence of youth (grades 9–12) and adult (age 18 and older) use of these products using data from the 2011 United States state-level Youth Risk Behaviors Surveillance System and the 2010–2011 United States National Survey on Drug Use and Health (NSDUH), respectively. We used the Pearson correlation coefficient to measure the associations. Results We found significant positive correlations between state Google Trends cigar relative search volume and prevalence of cigar use among youth (r=0.39, R2 = 0.154, p=0.018) and adults (r=0.49, R2 = 0.243, p<0.001). Similarly, we found that the correlations between state Google Trends smokeless tobacco relative search volume and prevalence of smokeless tobacco use among youth and adults were both positive and significant (r=0.46, R2 = 0.209, p=0.003 and r=0.48, R2 = 0.226, p<0.001, respectively). Conclusions The results of this study validate that Google Trends has the potential to be a valuable monitoring tool for tobacco use. The near real-time monitoring features of Google Trends may complement traditional surveillance methods and lead to faster and more convenient monitoring of emerging trends in tobacco use. © 2015, BMJ Publishing Group. All rights reserved

The impact of exposure model misspecification on signal detection in prospective pharmacovigilance

Purpose: Pharmacovigilance monitors the safety of drugs after their approval and marketing. Timely detection of adverse effects is important. The true relationship between time-varying drug use and the adverse event risk is typically unknown. Yet, most current pharmacovigilance studies rely on arbitrarily chosen exposure metrics such as current exposure or use in the past 3months. The authors used simulations to assess the impact of a misspecified exposure model on the timeliness of adverse effect detection. Methods: Prospective pharmacovigilance studies were simulated assuming different true relationships between time-varying drug use and the adverse event hazard. Simulated data were analyzed by fitting conventional parametric and more complex spline-based estimation models at multiple, pre-specified testing times. The 'signal' was generated on the basis of the corrected model-specific p-value selected to ensure a 5% probability of incorrectly rejecting the null hypothesis of no association. Results: Results indicated that use of an estimation model that diverged substantially from the true underlying association-reduced sensitivity and increased the time to detection of a clinically important association. Conclusions: Time to signal detection in pharmacovigilance may depend strongly on the method chosen to model the exposure. No single estimation model performed optimally across different simulated scenarios, suggesting the need for data-dependent criteria to select the model most appropriate for a given study. Copyright © 2014 John Wiley & Sons, Ltd.

Influenza seasonality in Madagascar: The mysterious African free-runner

Background: The seasonal drivers of influenza activity remain debated in tropical settings where epidemics are not clearly phased. Antananarivo is a particularly interesting case study because it is in Madagascar, an island situated in the tropics and with quantifiable connectivity levels to other countries. Objectives: We aimed at disentangling the role of environmental forcing and population fluxes on influenza seasonality in Madagascar. Methods: We compiled weekly counts of laboratory-confirmed influenza-positive specimens for the period 2002 to 2012 collected in Antananarivo, with data available from sub-Saharan countries and countries contributing most foreign travelers to Madagascar. Daily climate indicators were compiled for the study period. Results: Overall, influenza activity detected in Antananarivo predated that identified in temperate Northern Hemisphere locations. This activity presented poor temporal matching with viral activity in other countries from the African continent or countries highly connected to Madagascar excepted for A(H1N1)pdm09. Influenza detection in Antananarivo was not associated with travel activity and, although it was positively correlated with all climatic variables studied, such association was weak. Conclusions: The timing of influenza activity in Antananarivo is irregular, is not driven by climate, and does not align with that of countries in geographic proximity or highly connected to Madagascar. This work opens fresh questions regarding the drivers of influenza seasonality globally particularly in mid-latitude and less-connected regions to tailor vaccine strategies locally. © 2015 The Authors.

Adoption of preventive behaviors in response to the 2009 H1N1 influenza pandemic: A multiethnic perspective

Background: As public health leaders prepare for possible future influenza pandemics, the rapid spread of 2009 H1N1 influenza highlights the need to focus on measures the public can adopt to help slow disease transmission. Such measures may relate to hygiene (e.g., hand washing), social distancing (e.g., avoiding places where many people gather), and pharmaceutical interventions (e.g., vaccination). Given the disproportionate impact of public health emergencies on minority communities in the United States, it is important to understand whether there are differences in acceptance across racial/ethnic groups that could lead to targeted and more effective policies and communications. Objectives: This study explores racial/ethnic differences in the adoption of preventive behaviors during the 2009 H1N1 influenza pandemic. Patients/Methods: Data are from a national telephone poll conducted March 17 to April 11, 2010, among a representative sample of 1123 white, 330 African American, 317 Hispanic, 268 Asian, and 262 American Indian/Alaska Native adults in the USA. Results: People in at least one racial/ethnic minority group were more likely than whites to adopt several behaviors related to hygiene, social distancing, and healthcare access, including increased hand washing and talking with a healthcare provider (P-values <0·05). Exceptions included avoiding others with influenza-like illnesses and receiving 2009 H1N1 and seasonal influenza vaccinations. After we controlled the data for socioeconomic status, demographic factors, healthcare access, and illness- and vaccine-related attitudes, nearly all racial/ethnic differences in behaviors persisted. Conclusions: Minority groups appear to be receptive to several preventive behaviors, but barriers to vaccination are more pervasive. © 2015 The Authors.

Review: Evaluation of foot-and-mouth disease control using fault tree analysis

An outbreak of foot-and-mouth disease (FMD) causes huge economic losses and animal welfare problems. Although much can be learnt from past FMD outbreaks, several countries are not satisfied with their degree of contingency planning and aiming at more assurance that their control measures will be effective. The purpose of the present article was to develop a generic fault tree framework for the control of an FMD outbreak as a basis for systematic improvement and refinement of control activities and general preparedness. Fault trees are typically used in engineering to document pathways that can lead to an undesired event, that is, ineffective FMD control. The fault tree method allows risk managers to identify immature parts of the control system and to analyse the events or steps that will most probably delay rapid and effective disease control during a real outbreak. The present developed fault tree is generic and can be tailored to fit the specific needs of countries. For instance, the specific fault tree for the 2001 FMD outbreak in the UK was refined based on control weaknesses discussed in peer-reviewed articles. Furthermore, the specific fault tree based on the 2001 outbreak was applied to the subsequent FMD outbreak in 2007 to assess the refinement of control measures following the earlier, major outbreak. The FMD fault tree can assist risk managers to develop more refined and adequate control activities against FMD outbreaks and to find optimum strategies for rapid control. Further application using the current tree will be one of the basic measures for FMD control worldwide. © 2013 Blackwell Verlag GmbH.

Molecular identification of Ehrlichia species and host bloodmeal source in Amblyomma americanum L. from two locations in Tennessee, United States

The current status of tick-borne diseases in the southeastern United States is challenging to define due to emerging pathogens, uncertain tick/host relationships, and changing disease case definitions. A golf-oriented retirement community on the Cumberland Plateau in Tennessee experienced an ehrlichiosis outbreak in 1993, prompting efforts to reduce the local tick population using '4-Poster' acaricide devices targeting white-tailed deer ( Odocoileus virginianus). In 2009, the prevalence of Ehrlichia spp. in questing ticks was surveyed in the area and compared to a Tennessee state park where acaricide had not been applied. The range of wildlife hosts that immature Amblyomma americanum fed upon and the role that these hosts may play in pathogen dynamics were investigated using a reverse line blot (RLB) bloodmeal analysis technique. Amblyomma americanum was by far the most common tick species in both study areas (>99% of ticks collected). Of 303 adult and nymphal A. americanum tested at the retirement community, six were positive for Ehrlichia chaffeensis (2.0%), 16 were positive for E. ewingii (5.3%), and six were positive for Panola Mountain Ehrlichia (2.0%). This is the first confirmation of Panola Mountain Ehrlichia in A. americanum from the state of Tennessee. The 9.3% prevalence of Ehrlichia spp. in ticks from the retirement community was similar to that detected at the state park site (5.5%), suggesting that the 4-Poster treatment had not been sufficient to reduce Ehrlichia spp. cycling in the tick population. At both study sites, A. americanum fed on a wide range of mammal and bird species, with a minority of detectable bloodmeals coming from deer. Of the Ehrlichia-infected nymphs with positive bloodmeal identification, none fed on deer, indicating that multiple vertebrate species are contributing to sylvatic maintenance of Ehrlichia spp. at these sites. This highlights the difficulty of attempting to reduce the risk of tick-borne disease through host-targeted

Prevalence of Clostridium difficile infection in hospitalized patients with diarrhea: Results of a French prospective multicenter bi-annual point prevalence study [Prévalence des infections à Clostrid

Background: Clostridium difficile infections represent the major cause of healthcare-associated diarrhea. The objective of the study was to determine the incidence of C.difficile infection (CDI) in 2012 and to assess the under-estimation of the disease in France. Methods: Seventy healthcare facilities participated in a prospective point prevalence study. Each laboratory was requested to send all the diarrheal stool samples from hospitalized patients during 2 days (one in December 2012 and one in July 2013) to the National Reference Laboratory (NRL) for C.difficile, irrespective of a medical request for C.difficile. At the NRL, stool samples were analyzed using the Quik Chek Complete assay (Alere). Positive samples for glutamate deshydrogenase or toxins were confirmed by the toxigenic culture. Results obtained by the NRL were then compared to those given by each healthcare facility. Incidence of CDI in 2012 was provided by each healthcare facility through a specific questionnaire. Results: Mean incidence of CDI reported in 2012 by the HCF was 3.6 ± 2.9 per 10,000 patient-days; the incidence was positively correlated to the density testing (defined by the number of tests per 10,000 patient-days), which varied across the HCF (median 29.0 per 10,000 patient-days, IQR 19-50). During the bi-annual point prevalence survey, 651 stool samples were included and 90 were positive for C.difficile in culture. The overall prevalence of patients infected by a toxigenic C.difficile strain was 9.7% (63/651) and the prevalence of patients colonized by a non-toxigenic strain was 4.2% (27/651). Among the 65 cases of CDI detected by the NRL, 35 (55.6%) were missed by the participating HCF because of a lack of sensitivity of the methods used for the diagnosis (16/63, 25.4%) or because of a lack of clinical suspicion (19/63, 30.2%). Conclusion: The incidence of CDI in 2012 has increased in France compared to that of 2009 but is still underestimated because of a lack of clinical suspicion o

An Analysis of an Incomplete Marked Point Pattern of Heat-Related 911 Calls

We analyze an incomplete marked point pattern of heat-related 911 calls between the years 2006–2010 in Houston, TX, to primarily investigate conditions that are associated with increased vulnerability to heat-related morbidity and, secondarily, build a statistical model that can be used as a public health tool to predict the volume of 911 calls given a time frame and heat exposure. We model the calls as arising from a nonhomogenous Cox process with unknown intensity measure. By using the kernel convolution construction of a Gaussian process, the intensity surface is modeled using a low-dimensional representation and properly adheres to circular domain constraints. We account for the incomplete observations by marginalizing the joint intensity measure over the domain of the missing marks and also demonstrate model based imputation. We find that spatial regions of high risk for heat-related 911 calls are temporally dynamic with the highest risk occurring in urban areas during the day. We also find that elderly populations have an increased probability of calling 911 with heat-related issues than younger populations. Finally, the age of individuals and hour of the day with the highest intensity of heat-related 911 calls varies by race/ethnicity. Supplementary materials are included with this article. © 2015, American Statistical Association.

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