<div>Public health policies increasingly rely on complex models that need to approximate epidemics realistically and be consistent with the available data. Choosing appropriate simplifying assumptions is one of the critical challenges in disease modeling. In this thesis, we focus on some of these assumptions to show how they impact model outcomes. </div><div>In this thesis, an ODE model with a gamma-distributed infectious period is studied and compared with an exponentially distributed infectious period. We show that, for childhood diseases, isolating infected children is a possible mechanism causing oscillatory behavior in incidence. This is shown analytically by identifying a Hopf bifurcation with the isolation period as the bifurcation parameter. The threshold value for isolation to generate sustained oscillations from the model with gamma-distributed isolation period is much more realistic than the exponentially distributed model.</div><div><br></div><div>The consequences of not modeling the spectrum of clinical symptoms of the 2014 Ebola outbreak in Liberia include overestimating the basic reproduction number and effectiveness of control measures. The outcome of this model is compared with those of models with typical symptoms, excluding moderate ones. Our model captures the dynamics of the recent outbreak of Ebola in Liberia better, and the basic reproduction number is more consistent with the WHO response team's estimate. Additionally, the model with only typical symptoms overestimates the basic reproduction number and effectiveness of control measures and exaggerates changes in peak size attributable to interventions' timing.</div><div><br></div>

Childhood immunization has been one of the most important public health measures in the 20th century. In the United States, 95% of avoidable childhood diseases have been prevented through vaccinations. However, there have been growing concerns around the safety of vaccines, and this increased uncertainty has led to decreases in vaccination participation and increases in cases of preventable diseases. As such, is it important to understand why parents are not vaccinating their children. A qualitative approach was utilized to conduct this study. Flyers to recruit participants were distributed by healthcare providers and were posted in church facilities. Ten parents of children ages 3 to 8 years volunteered to participate to discuss their refusal to or delay in vaccinating their children. The health belief model functioned as the theoretical context to guide this phenomenological study approach in examining the reasons parents are not vaccinating or delaying vaccination of their children. Analysis included constructing a written description of the phenomenon as experienced by the research participants using their responses to the research question, followed by developing response coding schemes, identifying themes, justifying findings, and ensuring sound analysis and reporting of information. For example, word frequency and common phrases were the first steps of the analysis. Results showed that parents had a negative reaction towards childhood vaccination and felt that either the vaccine schedule was too aggressive or contained dangerous toxins that may have side effects. These findings can be used to assist healthcare providers in the way they provide outreach and education to parents as well as potentially helping develop tools that would encourage parents to vaccinate their children.

<p>Modelling and analysis of recurrent infectious disease epidemics often depends on the reconstruction of a time-varying transmission rate from historical reports of cases or deaths. Statistically rigorous estimation methods for time-varying transmission rates exist but are too computationally demanding to apply to a time series longer than a few decades. We present a computationally ecient estimation method that is suitable for very long data sets. Our method, which uses a discrete-time approximation to the SIR model for infectious diseases, is easy to implement and outperforms the classic Fine and Clarkson estimation method.</p> / Master of Science (MSc)

Thesis (MCur)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Parents and/or caregivers all over the world are expected to comply with existing childhood immunisation programmes in order to prevent outbreaks of preventable childhood diseases. The most important justification for this study was the 2010 measles outbreak in the Western Cape province of South Africa. This outbreak correlated with the study conclusions of Corrigall, Coetzee and Cameron (2008:41) as they found the immunisation coverage in the Western Cape to be insufficient to prevent outbreaks of preventable childhood diseases. From the literature, it seemed that attitudes and factors that influence parent and/or caregiver compliance with the routine childhood immunisation schedule in the Witzenberg sub-district of the Western Cape persist. In doing this study, the researcher’s purpose was to discover what those factors were. The aim was to determine, understand and describe the attitudes and factors influencing parent and/or caregiver compliance with the routine childhood immunisation schedule, and the nature thereof. The set objectives were to gain knowledge of and insight into the factors influencing participants’ adherence with routine childhood immunisation; and participants’ feelings, attitudes, and experiences surrounding immunisation within the context of their health care environment. A quantitative research approach, with a smaller qualitative component, was selected for this study which had an exploratory descriptive design. The population targeted for data collection included parents and/or caregivers of children aged 0 to 60 months in the Witzenberg sub-district (N=8374), as well as in community health centres (CHCs) that provided immunisation and/or other primary health care services in the mentioned subdistrict (N=16). The non-probability convenience sampling of parents and/or caregivers consisted of 376 participants (n=376), while 8 CHCs (n=8) were selected through systematic sampling. The measuring instrument used as the data collection technique for this study was a selfadministered questionnaire. A pilot study was conducted to pre-test the questionnaire, and its reliability and validity were further ensured by submitting it for review to research experts in methodology and nursing. A combination of quantitative and qualitative methods was used to analyse the study data. MS Excel was used to capture the quantitative data after which it was analysed using descriptive statistics by means of STATISTICA version 9-software. Tesch’s approach to qualitative data analysis was used as a guideline with the purpose of identifying and categorising the essential qualitative data and grouping it together in one descriptive framework. The main findings were that parents and/or caregivers involved in this study were positive about immunisation and their experiences within the health service environment. They also felt that health workers were playing an important role in their decision-making process. However, their knowledge regarding the purpose of and contra-indications for immunisation were insufficient, and most parents reported that their children experienced side effects after immunisation. Key recommendations on conclusion of the study include clear, accurate and specific information to parents about the purpose of immunisation and its contra-indications and side effects. Vaccinators and managers should be informed about the persistent problem with mild vaccination side effects and refresher courses should be provided with regard to infection control, administration techniques and the reporting of adverse effects. / AFRIKAANSE OPSOMMING: Daar word van ouers en/of versorgers oor die wêreld verwag om aan bestaande kinderimmunisasieprogramme te voldoen ter voorkoming van vaksien-voorkombare siektes. Die belangrikste regverdiging vir die studie was die masel-uitbreking in die Wes-Kaapprovinsie van Suid-Afrika in 2010. Die uitbraak het die studiebevindinge ondersteun van Corrigall, Coetzee en Cameron (2008:41), wat bevind het dat immunisasiedekking in die Wes-Kaap onvoldoende was om ʼn uitbreking van voorkombare kindersiektes te verhoed. Volgens die literatuur het dit voorgekom asof die gesindhede en faktore wat ouers en/of versorgers se houding jeens die roetine- kinder-immunisasieskedule in die Witzenberg sub-distrik van die Wes-Kaap beïnvloed, voortduur. Die navorser het met hierdie studie ten doel gehad om die faktore te ontdek, ten einde die gesindhede en faktore wat ‘n invloed uitoefen te bepaal, te verstaan en te omskryf. Die doelwitte was om kennis in te win oor en insig te verkry in die faktore wat ouers en/of versorgers se aanhanklikheid met routine kinder immunisering beinbloed; en in ouers en/of versorgers se gevoelens, houdings en ondervindings ten opsigte van immunisasie in hulle gesondheidsorg-omgewing. ‘n Kwantitatiewe navorsingsbenadering met ‘n kleiner kwalitatiewe komponent is geselekteer vir die studie wat ‘n ondersoekend-beskrywende navorsingsontwerp gehad het. Die populasie wat geteiken is vir data-insameling was ouers en/of versorgers van kinders van 0 tot 60 maande in die Witzenberg sub-distrik (N=8374), asook gemeenskapsgesondheidsentrums wat immunisasie en/of ander primêre gesondheidsorgdienste in die genoemde sub-distrik aanbied (N=16). Die nie-waarskynlike gerieflikheidsteekproef van ouers en/of versorgers het uit 376 deelnemers (n=376) bestaan, terwyl 8 (n=8) gemeenskapsgesondheidsentrums deur middel van sistematiese steekproefbepaling geselekteer is. Die meetinstrument vir data-insameling in die studie was self-geadministreerde vraelyste. ‘n Loodsstudie is uitgevoer as vooraf-toetsing van die vraelys en die geldigheid en betroubaarheid daarvan is verder verseker deur die vraelys aan navorsingskenners in navorsingsmetodologie en verpleging te onderwerp. ‘n Kombinasie van kwantitatiewe en kwalitatiewe metodes is gebruik vir die analisering van die studie-data. Die kwantitatiewe data is op MS Excel ingevoer waarna beskrywende statistieke deur middel van Statistica weergawe 9-sagteware gebruik is om dit te analiseer. Tesch se benadering tot kwalitatiewe data-analise is as riglyn gebruik met die doel om belangrike data te identifiseer, te kategoriseer en in ‘n beskrywende raamwerk te groepeer. In die studie is daar hoofsaaklik bevind dat ouers en/of versorgers positief is oor immunisasie en hul ondervinding binne die gesondheidsorgomgewing, en dat gesondheidswerkers ʼn belangrike rol in hul besluitnemingsproses speel. Hul kennis aangaande die doel van en kontra-indikasies vir immunisasie was egter onvoldoende en die meeste ouers en/of versorgers het gerapporteer dat hul kinders ná immunisasie probleme met newe-effekte ondervind het. Die hoofaanbevelings wat uit die studie voortgespruit het, was dat duidelike, akkurate en spesifieke inligting aan ouers en/of versorgers verskaf moet word aangaande die doel van immunisasie en die kontra-indikasies daarvoor. Immuniseerders en bestuurders moet ook ingelig word oor die voortdurende voorkoms van newe-effekte sodat opknappingskursusse oor infeksiebeheer, korrekte toedieningstegnieke en die rapportering van newe-effekte aangebied kan word.

OBJECTIVE/ METHOD The study examined implementation challenges faced by primary health care workers within the Ekurhuleni Metropolitan Municipality in Gauteng South Africa. Data collection was based on semi-structured interviews carried out on a purposive sample (n=19) of frontline clinicians working within the district as primary health care practitioners. RESULTS Participants confirmed that work within the primary health care service disproportionately focussed on curative and rehabilitative functions of their roles with little prioritisation of preventive and promotive interventions. Primary identified reasons included, institutional culture that prioritised short-term curative approaches. Clinicians also cited a range of other organisational barriers, such as – poor strategic planning, and a lack of understanding of health promotion and illness prevention. CONCLUSIONS Although the challenges that exist in implementing primary health care are clearly understood, clinicians perceive the solutions for these as being within the control of policy makers and those with power within the organisation. / Health Studies / M.A. (Public Health)

OBJECTIVE/ METHOD The study examined implementation challenges faced by primary health care workers within the Ekurhuleni Metropolitan Municipality in Gauteng South Africa. Data collection was based on semi-structured interviews carried out on a purposive sample (n=19) of frontline clinicians working within the district as primary health care practitioners. RESULTS Participants confirmed that work within the primary health care service disproportionately focussed on curative and rehabilitative functions of their roles with little prioritisation of preventive and promotive interventions. Primary identified reasons included, institutional culture that prioritised short-term curative approaches. Clinicians also cited a range of other organisational barriers, such as – poor strategic planning, and a lack of understanding of health promotion and illness prevention. CONCLUSIONS Although the challenges that exist in implementing primary health care are clearly understood, clinicians perceive the solutions for these as being within the control of policy makers and those with power within the organisation. / Health Studies / M.A. (Public Health)