Agent, host and environmental interactions | Occupational Medicine | Oxford Academic
Keywords: Epidemiologic Problem Oriented Approach, HIV/AIDS, Modeling marriage rates, number of sexual partners, sexual preferences, frequency of The first triad is composed of three pillars: the agent, host and environment pillars . In infectious disease models, the term "agent" originally referred to the entity or The diagram on the next tab sets out the agent, host and environmental factors. In this model, disease results from the interaction between the agent and the susceptible host in an environment that supports transmission of.
Principles of Epidemiology | Lesson 1 - Section 8
Confirmation of these results in studies using more comprehensive stress measurements may highlight stress prevention as important risk reduction for premature death in young and middle-aged men. Observational studies measure associations; however causal interpretation depends on study validity.
Stressed, depressed, and anxious folk can have different risk factor profiles. They may exercise less, smoke more, or be more obese than the general population.
Stress and depression are associated with physiologic changes like greater platelet aggregation, inflammatory markers, reduced heart rate variability, and overactivity of the hypothalamic-pituitary-adrenal system.
Perhaps this reflects a shared genetic liability as the same genes may be associated with depression and mortality through regulation of inflammatory or serotonergic pathways.
Epidemiology not only measures the relationships between hosts and agents in certain environments but also analyses the health status of the population living in that environment. Epidemiology has a long tradition and has created a wealth of accumulated experience to assess micro-environments and specific agents that may impact health. However, epidemiology has been infrequently applied to assessment of public health issues at the policy or strategic level.
In addition, epidemiology itself does not equip to deal with dialogue between stakeholders within its scientific discipline. There are different types of interventions tackling all three elements of the triangle. One can work with hosts and improve their immune system, increase their knowledge, and motivate behavioral change to make the hosts more resistant to agents. Public health can also influence the presence and distribution of agents vectors ; this is often done via traditional hygiene measures, such as provision of safe drinking water, clean air, and good waste management, but also via anti-smoking regulations, diet advice, and physical activity guidelines.
However, tackling the environment is a bit more difficult. This model of health is influenced by general political, social, and environmental conditions, and a set of social determinants of health, including work, education, culture, social cohesion, and individual behavior, as well as biological factors like age, sex, and genetics.
- Epidemiology, Population Health, and Health Impact Assessment
Health impact assessment HIA aims to influence general social, political, and environmental factors, as well as the social determinants of health. Because the goal of HIA is to assess potential future impacts of projects, plans, strategies, and policies on health, 4 HIA projects intervene in the environment.
Although there are several definitions of HIA and a confusion remains about what is and what is not HIA, the following three conditions must be met to be considered HIA: A policy, project, programme, or plan is assessed and a decision upon it is expected to be taken; 2. Distribution of effects across the population is described; and 3. HIA is based on values of democracy, equity, sustainable development, and ethical use of evidence.
All of these stakeholders constitute the steering group, which usually directs an HIA. One should understand the environment in its broadest possible sense; the social, economic, cultural, political, and physical environments are equally included and equally relevant. HIA is a broad methodology, including both qualitative and quantitative methods, such as risk communication, risk assessment, and stakeholder analysis.
Lesson 1: Introduction to Epidemiology
Usually, HIA utilizes knowledge gathered by basic disciplines of public health, such as epidemiology, to outline potential health impacts and quantify them. However, HIA can work in the opposite way as well; HIA often identifies areas where we know little about the interaction of hosts and agents in a specific environment.
In other words, HIA cannot be done without substantial contributions from epidemiologists but can help to identify concrete relationships where we lack quantitative knowledge and provide epidemiology with new research themes. In this model, disease results from the interaction between the agent and the susceptible host in an environment that supports transmission of the agent from a source to that host. Two ways of depicting this model are shown in Figure 1. Agent, host, and environmental factors interrelate in a variety of complex ways to produce disease.
Different diseases require different balances and interactions of these three components. Development of appropriate, practical, and effective public health measures to control or prevent disease usually requires assessment of all three components and their interactions. Generally, the agent must be present for disease to occur; however, presence of that agent alone is not always sufficient to cause disease. A variety of factors influence whether exposure to an organism will result in disease, including the organism's pathogenicity ability to cause disease and dose.
Over time, the concept of agent has been broadened to include chemical and physical causes of disease or injury. These include chemical contaminants such as the L-tryptophan contaminant responsible for eosinophilia-myalgia syndromeas well as physical forces such as repetitive mechanical forces associated with carpal tunnel syndrome. While the epidemiologic triad serves as a useful model for many diseases, it has proven inadequate for cardiovascular disease, cancer, and other diseases that appear to have multiple contributing causes without a single necessary one.
Host refers to the human who can get the disease. A variety of factors intrinsic to the host, sometimes called risk factors, can influence an individual's exposure, susceptibility, or response to a causative agent. Opportunities for exposure are often influenced by behaviors such as sexual practices, hygiene, and other personal choices as well as by age and sex. Susceptibility and response to an agent are influenced by factors such as genetic composition, nutritional and immunologic status, anatomic structure, presence of disease or medications, and psychological makeup.
Environment refers to extrinsic factors that affect the agent and the opportunity for exposure. Environmental factors include physical factors such as geology and climate, biologic factors such as insects that transmit the agent, and socioeconomic factors such as crowding, sanitation, and the availability of health services.