Principles of Epidemiology

Global health | 2nd lec sum. | "upon } epidemiology Principles of Epidemiology: Epidemiology: the science which deals with what falls upon people, - It is an investigative method to detect the cause or source of diseases, disorders, syndromes, conditions, or perils that cause pain, injury, illness, disability, or death. - It studys the occurrence and distribution of health-related diseases or events in specified populations, including the study of the determinants influencing such states, and the application of this knowledge to control the health problem. - It also involves characterizing the distribution of heath status, diseases, or other health problems in terms of age, sex, race, geography, religion, education, occupation, behaviors, time, place, person, etc. - It serves as the foundation and logic of interventions made in the interest of public health and preventive medicine. - It is considered a cornerstone methodology of public health research, and is highly regarded in evidence-based medicine for identifying risk factors for disease and determining optimal treatment approaches to clinical practice. - In the work of communicable and non-communicable diseases, the work of epidemiologists range from outbreak investigation to study design, data collection and analysis including the development of statistical models to test hypotheses and the documentation of results for submission to peer-reviewed journals. Epidemiologists may draw on a number of other scientific disciplines such as biology in understanding disease processes and social science disciplines including sociology and philosophy in order to better understand proximate and distal risk factors. Purposes of Epidemiology: 1. To explain the etiology (cause) of a single disease or group of diseases using information management. 2. To study the history and trends of a disease. 3. To determine if data are consistent with proposed hypothesis. 4. To provide a basis for developing control measures and prevention procedures for groups and at risk populations. 5. it DOES NOT provide solutions or medical intervention (eg; medicine, treatment, protocols,..) *these things are decided based on epidemiological multidisciplinary approaches. - Terms: - The Epidemiologist: a professional who study and control the factors that influence the occurrence of disease or health-related conditions and events in specified populations, has an experience in population thinking and epidemiologic methods, and is knowledgeable about public health and causal inference in health. - Disease: a 1. pattern of response by a living organism to the invasion of a foreign substance or injury which causes an alteration of the organisms normal functioning. also, it is an 2. abnormal state in which the body is not capable of responding to or carrying on its normally required functions. - Pathogens: organisms or substances such as bacteria, viruses, or parasites that are capable of producing diseases. Pathogenesis: the development, production, or process of generating a disease. Pathogenicity: the potential ability and strength of a pathogenic substance to cause disease (the difference in the extent of the disease from one pathogen to another). Infective diseases: are those which the pathogen has the capability to enter, survive, and multiply in the host (communicable disease). - Virulence: 1. the extent of pathogenicity or strength of different organisms. 2. the ability of the pathogen to grow, thrive, and to develop all factor into virulence. 3. the capacity and strength of the disease to produce severe and fatal cases of illness. There is NO difference between virulence and pathogenicity. Invasiveness: the ability to get into a susceptible host and cause a disease within the host - The capacity of a microorganism to enter into and grow in or upon tissues of a host. The ability to invade the host, as opposed to the ability to cause disease (pathogenicity) Etiology: the factors contributing to the source of or causation of a disease. Toxins: a poisonous substance that is a specific product of the metabolic activities of a living organism and is usually very unstable (notably toxic when introduced into tissues, & typically capable of inducing antibody formation). - Antibiotics: a substance produced by or a semisynthetic substance derived from a microorganism and able in dilute solution to inhibit or kill another microorganism. Endemic: the ongoing, usual level of, or constant presence of a disease in a given population. Or, disease present among a population at all times. Eg: Malaria in some African Regions Hyperendemic: persistent level of activity beyond or above the expected prevalence. - Holoendemic: a disease that is highly prevalent in a population & is commonly acquired early in children of the population. (differs from endemic, in that the whole population has it) Epidemic: outbreak or occurrence of one specific disease from a single source, in a group population, community, or geographical area, in excess of the usual level of expectancy. Can progress into a pandemic. - Pandemic: epidemic that is widespread across a country, continent, or large populace, possible worldwide. Claiming diseases as an epidemic vs pandemic is decided by international organizations, it has extreme and substantial political and geographical applications on all people. - Despite having cases recorded all around the world, SARS is considered an epidemic because of multifactorial interference from political and economic groups as well as international organizations. Covid wasn't considered a pandemic till relatively late because of the same pressures. Incidence: the extent that people, within a population who do not have a disease, develop the disease during a specific time period. [# of new cases of disease / total # at risk]. - Prevalence: the number of people within a population who have a certain disease at a given point in time. # cases existing at one time. - Prevalence relies on 2 factors: 1. How many people have had the disease in the past 2. Duration of the disease in the population Incidence # of New Cases in a Given Population in a Specified Time | Population at Risk in That Time Period. Prevalence # of Existing Cases in a Given Population at a Single Point in Time | Population at That Time. Comparing Population Characteristics: Rates help us compare health problems among different populations that include two or more groups who differ by a selected characteristic. - The Epidemiology Triangle: - Outbreaks in a population often involves several factor and entities. - Many people, objects, avenues of transmission, and organisms can be involved in the spread of disease. - The epidemiology triangle help explain the multifaceted phenomena of disease transmission. - Many diseases rely on an agent or single factor for an infectious disease to occur. - Epidemiologist use an ecological view to assess the interaction of various elements and factors in the environment and disease-related implications. - When more than a single cause must be present for a disease to occur, this is called multiple causation. - The interrelatedness of 4 factors contribute to the outbreak of a disease: 1. Role of the host 2. Agent 3. Environmental circumstances 4. Time - The epidemiology triangle is used to analyze the role and interrelatedness of each of the four factors in epidemiology of infectious diseases, that is the influence, reactivity and effect each factor has on the other three. 1. The agent is the cause of the disease (can be living or nonliving) • Can be bacteria, virus, parasite, fungus, mold • Chemicals (solvents), Radiation, heat, naturaltoxins (snake or spider venom) 2. The host is an organism, usually human or animal, that harbors the disease. • Level of immunity, genetic make-up, state of health, and overall fitness within the host can determine the effect of a disease can have upon it. 3. The environment is the favorable surroundings and conditions external to the human or animal that cause or allow the disease or allow disease transmission. • Environmental factors can include the biological & the social aspects, cultural, and physical aspects of the environment. 4. The time accounts for incubation periods, life expectancy of the host or pathogen, duration of the course of illness or condition (acute, subacute, or chronic) «Салайне Та Tim