1,720,984 research outputs found
Estimating Infectious Disease Parameters for the Transmission of Malaria in Ugandan Children
No full textIn this thesis, we used malaria data from Ugandan children to estimate malaria-related mortality and determinants. We derived a link between mathematical and statistical models enabling the estimation of the malaria prevalence and force of infection (FOI) by assuming an SIS compartmental model and the generalised linear mixed model (GLMM). Finally we developed a methodology to account for outcome-dependent sampling (ODS) using a joint model. The results indicated that malaria is the leading cause of death among children who died when aged 29 days to 14 years in some parts in Uganda. The mortality hazard was higher among children who had fever or those that were admitted in the health centres or those who died on the way to seek care. The malaria prevalence and FOI were highest among children aged 5-10 years in areas with high transmission intensities and were highest among children aged about 1 year in areas of low transmission intensities. Children who were previously asymptomatic had higher hazards of being re-infected with malaria compared to their counterparts who were symptomatic. Heterogeneity in malaria infection was quantified and was highest between households compared to between household members. The simulation study indicated that ignoring ODS could lead to biased estimates which would later lead to incorrect assessment of intervention strategies.VLIR, and NI
Estimating Infectious Disease Parameters for the Transmission of Malaria in Ugandan Children
No full textIn this thesis, we used malaria data from Ugandan children to estimate malaria-related mortality and determinants. We derived a link between mathematical and statistical models enabling the estimation of the malaria prevalence and force of infection (FOI) by assuming an SIS compartmental model and the generalised linear mixed model (GLMM). Finally we developed a methodology to account for outcome-dependent sampling (ODS) using a joint model. The results indicated that malaria is the leading cause of death among children who died when aged 29 days to 14 years in some parts in Uganda. The mortality hazard was higher among children who had fever or those that were admitted in the health centres or those who died on the way to seek care. The malaria prevalence and FOI were highest among children aged 5-10 years in areas with high transmission intensities and were highest among children aged about 1 year in areas of low transmission intensities. Children who were previously asymptomatic had higher hazards of being re-infected with malaria compared to their counterparts who were symptomatic. Heterogeneity in malaria infection was quantified and was highest between households compared to between household members. The simulation study indicated that ignoring ODS could lead to biased estimates which would later lead to incorrect assessment of intervention strategies.VLIR, and NI
Modelling longitudinal binary outcomes with outcome dependent observation times: an application to a malaria cohort study
No full textBACKGROUND : In spite of the global reduction of 21% in malaria incidence between 2010 and 2015, the disease still threatens many lives of children and pregnant mothers in African countries. A correct assessment and evaluation of the impact of malaria control strategies still remains quintessential in order to eliminate the disease and its burden. Malaria follow-up studies typically involve routine visits at pre-scheduled time points and/or clinical visits whenever individuals experience malaria-like symptoms. In the latter case, infection triggers outcome assessment, thereby leading to outcome-dependent sampling (ODS). Commonly used methods to analyze such longitudinal data ignore ODS and potentially lead to biased estimates of malaria-specific transmission parameters, hence, inducing an incorrect assessment and evaluation of malaria control strategies. METHODS : In this paper, a new method is proposed to handle ODS by use of a joint model for the longitudinal binary outcome measured at routine visits and the clinical event times. The methodology is applied to malaria parasitaemia data from a cohort of [Formula: see text] Ugandan children aged 0.5–10 years from 3 regions (Walukuba—300 children, Kihihi—355 children and Nagongera—333 children) with varying transmission intensities (entomological inoculation rate equal to 2.8, 32 and 310 infectious bites per unit year, respectively) collected between 2011–2014. RESULTS : The results indicate that malaria parasite prevalence and force of infection (FOI) increase with age in the region of high malaria intensity with highest FOI in age group 5–10 years. For the region of medium intensity, the prevalence slightly increases with age and the FOI for the routine process is highest in age group 5–10 years, yet for the clinical infections, the FOI gradually decreases with increasing age. For the region with low intensity, both the prevalence and FOI peak at the age of 1 year after which the former remains constant with age yet the latter suddenly decreases with age for the clinically observed infections. CONCLUSION : Malaria parasite prevalence and FOI increase with age in the region of high malaria intensity. In all study sites, both the prevalence and FOI are highest among previously asymptomatic children and lowest among their symptomatic counterparts. Using a simulation study inspired by the malaria data at hand, the proposed methodology shows to have the smallest bias, especially when consecutive positive malaria parasitaemia presence results within a time period of 35 days were considered to be due to the same infection. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12936-022-04386-1
Home management of malaria compared to the current standard of care for management of febrile illnesses in a cohort of Ugandan children ages 1 to <6 years
No full textTitle: Home Management of Malaria Compared to the Current Standard of Care for Management of Febrile Illnesses in a Cohort of Ugandan Children
Background: Home management of malaria, promoting presumptive treatment of febrile children at or near home with antimalarial drugs, is advocated to improve prompt effective treatment of malaria in Africa. In Uganda, a policy of home-based management of fever (HBMF) has been adopted, but evidence of the effectiveness of the program is limited.
Objectives: In this study, home delivery of artemether-lumefantrine (AL) for presumptive treatment of fever in children aged less than six years was compared to the current standard of care for childhood fever in Kampala, Uganda. The impact on health indicators, treatment actions and outcomes, and predictors of illness and treatment practices were assessed.
Methodology: In this study, households were randomized to either HBMF or standard care, and children were followed prospectively; observ
Home management of malaria compared to the current standard of care for management of febrile illnesses in a cohort of Ugandan children ages 1 to <6 years
No full textTitle: Home Management of Malaria Compared to the Current Standard of Care for Management of Febrile Illnesses in a Cohort of Ugandan Children
Background: Home management of malaria, promoting presumptive treatment of febrile children at or near home with antimalarial drugs, is advocated to improve prompt effective treatment of malaria in Africa. In Uganda, a policy of home-based management of fever (HBMF) has been adopted, but evidence of the effectiveness of the program is limited.
Objectives: In this study, home delivery of artemether-lumefantrine (AL) for presumptive treatment of fever in children aged less than six years was compared to the current standard of care for childhood fever in Kampala, Uganda. The impact on health indicators, treatment actions and outcomes, and predictors of illness and treatment practices were assessed.
Methodology: In this study, households were randomized to either HBMF or standard care, and children were followed prospectively; observ
Estimating the optimal interval between rounds of indoor residual spraying of insecticide using malaria incidence data from cohort studies
No full textAbstract: Background Indoor residual spraying (IRS) reduces vector densities and malaria transmission, however, the most effective spraying intervals for IRS have not been well established. We estimated the optimal timing interval for IRS using a statistical approach. Methods Six rounds of IRS were implemented in Tororo District, a historically high malaria transmission setting in Uganda, during the study period (3 rounds with bendiocarb active ingredient (Ficam (R)): December 2014 to December 2015, and 3 rounds with pirimiphos methyl active ingredient (Actellic 300 (R) CS): June 2016 to July 2018). A generalized additive model was used to estimate the optimal timing interval for IRS based on the predicted malaria incidence. The model was fitted to clinical incidence data from a cohort of children aged 0.5-10 years from selected households observed throughout the study period. Results 494 children, 67% aged less than 5 years at enrolment were analysed. Six-months period incidence of malaria decreased from 2.96 per person-years at the baseline to 1.74 following the first round of IRS and then to 0.02 after 6 rounds of IRS. The optimal time interval for IRS differed between bendiocarb and pirimiphos methyl and by IRS round. To retain an optimum impact, bendiocarb would require respraying 17 (95% CI: 14.2-21.0) weeks after application whereas pirimiphos methyl could remain impactful for 40 (95% CI: 37.0-42.8) weeks, although in the final year this estimates 36 (95% CI: 32.7-37.7) weeks. However, we could not estimate from the data the optimal time after the second and third rounds of bendiocarb and after the second round of pirimiphos methyl. Neither the amount of rainfall nor the EIR nor the distribution of nets were found to be statistically significant for determining the time period between spray rounds. Conclusion In our setting, the effect of the two IRS products was distinct. Statistically, pirimiphos methyl provided a longer window of protection than bendiocarb, although impact varied between different spray rounds and years which was not explained by rainfall or EIR or distribution of nets in our statistical approach. Understanding the effectiveness of IRS and how long it lasts can help for planning campaigns, but one should consider the financial cost and insecticide resistance. Monitoring the timing of spray campaigns using clinical incidence could be repeated in future programs to help determine the average period of protectivity of these products
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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