Current Issue : April - June Volume : 2014 Issue Number : 2 Articles : 7 Articles
Background: A forecast can be defined as an endeavor to quantitatively estimate a future event or probabilities\r\nassigned to a future occurrence. Forecasting stochastic processes such as epidemics is challenging since there are\r\nseveral biological, behavioral, and environmental factors that influence the number of cases observed at each point\r\nduring an epidemic. However, accurate forecasts of epidemics would impact timely and effective implementation of\r\npublic health interventions. In this study, we introduce a Dirichlet process (DP) model for classifying and forecasting\r\ninfluenza epidemic curves.\r\nMethods: The DP model is a nonparametric Bayesian approach that enables the matching of current influenza\r\nactivity to simulated and historical patterns, identifies epidemic curves different from those observed in the past and\r\nenables prediction of the expected epidemic peak time. The method was validated using simulated influenza\r\nepidemics from an individual-based model and the accuracy was compared to that of the tree-based classification\r\ntechnique, Random Forest (RF), which has been shown to achieve high accuracy in the early prediction of epidemic\r\ncurves using a classification approach. We also applied the method to forecasting influenza outbreaks in the United\r\nStates from 1997ââ?¬â??2013 using influenza-like illness (ILI) data from the Centers for Disease Control and Prevention (CDC).\r\nResults: We made the following observations. First, the DP model performed as well as RF in identifying several of the\r\nsimulated epidemics. Second, the DP model correctly forecasted the peak time several days in advance for most of\r\nthe simulated epidemics. Third, the accuracy of identifying epidemics different from those already observed improved\r\nwith additional data, as expected. Fourth, both methods correctly classified epidemics with higher reproduction\r\nnumbers (R) with a higher accuracy compared to epidemics with lower R values. Lastly, in the classification of seasonal\r\ninfluenza epidemics based on ILI data from the CDC, the methodsââ?¬â?¢ performance was comparable.\r\nConclusions: Although RF requires less computational time compared to the DP model, the algorithm is fully\r\nsupervised implying that epidemic curves different from those previously observed will always be misclassified. In\r\ncontrast, the DP model can be unsupervised, semi-supervised or fully supervised. Since both methods have their\r\nrelative merits, an approach that uses both RF and the DP model could be beneficial....
Background: There is urgent need for effective HIV prevention methods that women can initiate. The CAPRISA 004\r\ntrial showed that a tenofovir-based vaginal microbicide had significant impact on HIV incidence among women.\r\nThis study uses the trial findings to estimate the population-level impact of the gel on HIV and HSV-2 transmission,\r\nand price thresholds at which widespread product introduction would be as cost-effective as male circumcision in\r\nurban South Africa.\r\nMethods: The estimated ââ?¬Ë?per sex-actââ?¬â?¢ HIV and HSV-2 efficacies were imputed from CAPRISA 004. A dynamic HIV/STI\r\ntransmission model, parameterised and fitted to Gauteng (HIV prevalence of 16.9% in 2008), South Africa, was used\r\nto estimate the impact of gel use over 15 years. Uptake was assumed to increase linearly to 30% over 10 years, with\r\ngel use in 72% of sex-acts. Full economic programme and averted HIV treatment costs were modelled. Cost per\r\nDALY averted is estimated and a microbicide price that equalises its cost-effectiveness to that of male circumcision\r\nis estimated.\r\nResults: Using plausible assumptions about product introduction, we predict that tenofovir gel use could lead to a\r\n12.5% and 4.9% reduction in HIV and HSV-2 incidence respectively, by year 15. Microbicide introduction is predicted\r\nto be highly cost-effective (under $300 per DALY averted), though the dose price would need to be just $0.12 to\r\nbe equally cost-effective as male circumcision. A single dose or highly effective (83% HIV efficacy per sex-act)\r\nregimen would allow for more realistic threshold prices ($0.25 and $0.33 per dose, respectively).\r\nConclusions: These findings show that an effective coitally-dependent microbicide could reduce HIV incidence by\r\n12.5% in this setting, if current condom use is maintained. For microbicides to be in the range of the most\r\ncost-effective HIV prevention interventions, product costs will need to decrease substantially....
this country was accompanied by contradictory information, while worries about wide-spread influenza led to\r\ndiscrimination worldwide. Early understanding of public threat perceptions is therefore important for effective\r\npublic health communication and intervention.\r\nMethods: We interviewed 1011 respondents by phone two weeks after the first case. Questions examined risk\r\nawareness and media use, beliefs about the emergence of the threat and those most at risk, anxiety about\r\ninfection and preventive and avoidant behaviours.\r\nResults: Results demonstrate moderate levels of anxiety but relatively high levels of trust towards government\r\nofficials. Threat emergence was associated with hygiene levels, temperature change, floating pigs in the Huangpu\r\nRiver and migration to the city. Anxiety predicted both recommended and non-recommended behavioural\r\nchanges.\r\nConclusions: Comparatively high levels of trust in Chinese government advice about H7N9 contrast positively with\r\nprevious pandemic communications in China. Anxiety helped drive both recommended and non-recommended\r\nbehaviours, with potentially important economic and social implications. This included evidence of ââ?¬Ë?otheringââ?¬â?¢ of\r\nthose associated with the threat (e.g. migrants). Findings emphasise the need to manage public communications\r\nearly during new influenza outbreaks....
Tuberculosis is considered highly zoonotic wide spread disease. specimens were subjected to bacteriological study including microscopical by ZN stained smear, culture onto L-J medium and identification of isolates by biochemical reaction. In the current study using Dot blot, and dipstick tests (A new simple tuberculosis screening tests) are, economic, inexpensive compared with ELISA and LCD array test. Dot blot test produces results in less than 150 mins, while in case of dipstick test gives results in less than 30 minutes; these tests could be particularly useful in developing countries or remote areas that may lack access to expensive testing equipment for diagnosis of tuberculosis. The sensitivities and specificities were higher in the current study compared with other diagnosis commercial kits....
Background: After the largest outbreaks of Q fever ever recorded in history occurred in the Netherlands, concern\r\narose that Coxiella may be transmitted via donated tissues of latent or chronically infected donors. The Dutch\r\nHealth Council recently advised to screen tissue donors, donating high risk tissues, for Coxiella infection.\r\nMethods: After validation of an enzyme immunoassay (EIA) test for IgG antibodies against phase 2 of C. burnetii for\r\nuse on post-mortem samples, serum samples of 1033 consecutive Dutch post-mortem tissue donors were tested\r\nfor IgG antibodies against phase 2 of C. burnetii. Confirmation of reactive results was done by immunofluorescence\r\nassay (IFA). All available tissues (corneas, heart valves, skin and bone marrow) from donors with IgG reactivity were\r\ntested for presence of Coxiella DNA by PCR. Risk factors for IgG reactivity were investigated.\r\nResults: After validation of the tests for use on post-mortem samples, 50/1033 donors (4.8%) screened positive for\r\nphase 2 anti-Coxiella IgG by EIA, and 31 were confirmed by IFA (3.0%). One donor showed a serological profile\r\ncompatible with chronic infection. All tested tissues (25 corneas, 6 heart valves, 4 skin and 3 bone marrow) from\r\ndonors with IgG reactivity tested negative for the presence of Coxiella DNA. Except for living in a postal code area\r\nwith a high number of Q fever notifications, no risk factors for IgG reactivity were found.\r\nConclusions: The strong correlation between notifications and seroprevalence confirms that the used assays are\r\nsufficiently specific for use on post-mortem samples, although one has to be aware of differences between batches.\r\nThus, this study provides a validated method for screening tissue donors for infection with Coxiella burnetii that can\r\nbe used in future outbreaks....
Background: Chlamydia trachomatis is the most prevalent bacterial sexually transmitted infection (STI) worldwide.\r\nA strong link between C. trachomatis serogroup/serovar and serological response has been suggested in a previous\r\npreliminary study. The aim of the current study was to confirm and strengthen those findings about serological IgG\r\nresponses in relation to C. trachomatis serogroups and serovars.\r\nMethods: The study population (n = 718) consisted of two patient groups with similar characteristics of Dutch STI\r\nclinic visitors. We performed genotyping of serovars and used titre based and quantitative commercially available\r\nELISA kits (medac Diagnostika) to determine specific serum IgG levels. Optical density (OD) values generated by\r\nboth tests were used to calculate the IgG titres (cut-off 1:50). Analyses were conducted stratified by gender.\r\nResults: We observed very significant differences when comparing the median IgG titres of three serogroups, B, C\r\nand I: in women for B vs. C: p < 0.0001 (median titres B 200 vs. C <50); B vs. I: p < 0.0001 (200 vs. 50), and in men for\r\nB vs. C: p = 0.0006 (150 vs. <50); B vs. I: p = 0.0001 (150 vs. <50); C vs. I was not significant for both sexes. Serovars D\r\nand E of serogroup B had the highest median IgG titres compared to the other serovars in both men and women:\r\n200 and 200 vs. = 100 for women and 100 and 200 vs. = 75 for men, respectively.\r\nConclusions: This study shows that B group serovars induce higher serological responses compared to the C and I\r\ngroup serovars in vivo in both men and women...
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