A quantitative risk assessment for the likelihood of introduction of highly pathogenic avian influenza virus strain H5N1 into U.S. hunter retriever dogs.

Highly pathogenic avian influenza (HPAI) strain H5N1 has received great attention with regard to its potential spread to North America. This quantitative risk assessment, which is primarily based on wild bird carriage of HPAI from East Asia to Alaska, was conducted to assess the likelihood of a hunter retriever dog becoming infected after harvesting an infected waterfowl during the Alaskan hunting season. Using Monte Carlo Simulation with @Risk software, the expected probability of a hunter retriever dog becoming infected is 2.3 x 10(-8). This model can serve as a tool for decision makers in assessing the risk of HPAI strain H5N1 introduction into Alaska's hunter retriever dogs.

Epidemiologic Modeling of HIV/AIDS: Use of Computational Models to Study the Population Dynamics of the Disease to Assess Effective Intervention Strategies for Decision-making.

Computational models and simulations are becoming central research tools in epidemiology, biology, and other fields. Epidemiologic research involves the study of a complex set of host, environment and causative agent factors as these interact to impact health and diseases in any population. The most advanced of these efforts have focused on micro (cellular) or macro (human) population levels. The dynamic interplay of HIV with a focus in its hosts at the cellular level provides the micro-epidemiologic basis, while the dynamic interplay of multifactorial determinants: biomedical, behavioral, and socioeconomic factors provide the macro-epidemiologic basis at the human population level. We have developed the computational tools and mathematical approaches to study the population-level effects of various drugs on HIV to integrate models from micro to macro- levels in a seamless fashion. The critical variables that facilitate transmission of HIV and intracellular interactions and molecular kinetics were considered. Such multilevel models are essential if we are to develop quantitative, predictive models of complex biological systems such as HIV/AIDS.

A Conceptual Multivariate Modelling Approach for Integrating Epidemiologic and Psychosocial Determinants to Examine the Epidemiology of Diseases in Under-served Populations.

Epidemiologic research involves the study of a complex set of host, environment and causative agent factors as these interact to impact health and diseases in any population. A conceptual multivariate modelling approach for integrating epidemiologic and psychosocial determinants to examine the epidemiology of chronic and infectious diseases in under-served populations in the USA was developed. Our approach relies upon systems analysis, i.e. integrating concepts and methods in epidemiology with mathematics and statistics along with computational methods and tools to rigorously examine the dynamics of diseases such as the Human Immunodeficiency Virus/Acquired Immunodeficiency Syndrome (HIV/AIDS) in a community. We used a multifactorial and quantitative epidemiologic (static) model that interrelates multiple determinants including biomedical, behavioral, and socioeconomic factors to analyze morbidity and mortality due to HIV/AIDS. The research involved participation of the community in the collection of socioeconomic, demographic, environmental, epidemiologic and biomedical data. In collaboration with Montgomery AIDS Outreach (MAO), a community based Organization in Montgomery, Alabama; blood samples were collected and tested using Orasure HIV testing kits to establish infection status with HIV/AIDS. Using these models, evaluations of various intervention scenarios with the objective of recommending effective strategies to minimize the risk of new HIV infections and/or manage existing diseases in a community can be generated.

Developing a Generic Risk Assessment Simulation Modelling Software Tool for Assessing the Risk of Foot and Mouth Virus Introduction.

Foot and Mouth disease (FMD) is a highly contagious viral disease that affects all cloven-hoofed animals. Because of its devastating effects on the agricultural industry, many countries take measures to stop the introduction of FMD virus into their countries. Decision makers at multiple levels of the United States Department of Agriculture (USDA) use Risk Assessments (RAs) (both quantitative and qualitative) to make better and more informed scientifically based decisions to prevent the accidental or intentional introduction of the disease. There is a need for a generic RA that can be applied to any country (whether FMD free or non-FMD free) and for any product (FMD infected animals and animal products). We developed a user-friendly generic RA tool (software) that can be used to conduct and examine different scenarios of quantitative/qualitative risk assessments for the different countries with their varying FMD statuses in relation to reintroduction of FMD virus into the USA. The program was written in Microsoft Visual Basic 6.0 (Microsoft Corporation, Redmond, Washington, USA). The @Risk 6.1 Developer Kit (RDK) and @Risk 6.1 Best Fit Kit library (Palisade Corporation, Newfield, NY.USA) was used to build Monte Carlo simulation models. Microsoft Access 2000 (Microsoft Corporation, Redmond, Washington, USA) was used and SQL to query the data. Different input probability distributions can be selected for the nodes in the scenario tree and different output for each end-state of the simulation is given in different graphical formats and statistical values are used in describing the likelihood of FMD virus introduction. Sensitivity Analysis in determining which input factor has more effect on the total risk outputs is also given. The developed generic RA tools can be eventually extended and modified to conduct RAs for other animal diseases and animal products.

Modelling viral and CD4 cellular population dynamics in HIV: approaches to evaluate intervention strategies.

Computational models, such as in epidemiology, provide a powerful tool that can be used to systematically examine an array of dynamic interactions among populations as well as to evaluate altemate disease intervention strategies. The specific objectives in this study were to: a/ examine the interaction of cellular (CD4) and HIV population dynamics and evaluate the impact of the use of combination chemotherapies on viral and CD4 populations (Experiment #1), b/ demonstrate how modelling can be used to evaluate the impact of an intervention (condom use) on reducing the rate of HIV/AIDS (Experiment #2). In this study, we used state transition models and conducted simulation experiments to evaluate various alternatives for the control and/or prevention of HIV/AIDS. The result indicated that combination therapy (double or triple drug therapies) was very effective. The HIV viral population decreased rapidly and remained suppressed for years. On the other hand, the CD4 cell population increased above 400 cells per ml and was maintained above that level for many years. Mono-therapy was not as effective; although the viral load decreased rapidly, it increased to its original levels within a few months. Since condom use is one of the key interventions of HIV/AIDS, we evaluated its use in 25%, 50% and 75% of an adult, sexually active population. Increasing condom use by 50% and 75% above an estimated baseline of 25% reduced the incidence of AIDS by 53% in Blacks, 49% in Hispanics and 43% in Whites. The study shows how a cellular/molecular level model can be incorporated within a macro-epidemiologic systems dynamics model to evaluate a variety of scientific questions such as to see if cellular/molecular level interventions reduce morbidity and mortality rates in HIV.

A risk-assessment model for foot and mouth disease (FMD) virus introduction through deboned beef importation.

We present a risk-assessment model to assess the risk of introduction of foot and mouth disease (FMD) virus associated with deboned beef importation. The model was developed in accordance with the risk-reduction procedures proposed by the European Community for meat importation. The risk reduction procedures include farm-level inspection, ante-mortem inspection, post-mortem inspection, chilling and deboning. The risk assessment was based on the prevalence of FMD-infected cattle in herds as well as the prevalence of infected herds in the exporting country. Computer simulations were carried out to evaluate the probability of FMD virus introduction by importing 100 tons of deboned beef in relation to FMD prevalence, number of cattle selected from each herd, and sample sizes in ante-mortem and post-mortem inspections. The effects of the risk-reduction procedures on the probability of FMD virus introduction were examined.