Epi – Flashcard
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What is the definition of epidemiology using the Greek roots?
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Epi- -demos- -logy (what is) upon population the study of
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Do we study individuals or populations in epidemiology? Why?
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Populations. To learn the distribution and risk factors of illness and death so that strategies can be developed and implemented to prevent, mitigate, and control disease/health problems.
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Give examples of primary, secondary, and tertiary prevention?
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Primary prevention: (decrease incidence) to prevent disease onset /e.g. vaccination, enhance nutritional status, eliminate environmental risks Secondary prevention: (decrease prevalence by shortening duration) to cure disease/e.g. early detection w prompt intervention, screening programs, antibiotics Tertiary prevention: (reduce number and impact of complications) e.g. rehabilitation, environmental alterations such as handicap ramps
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What is the underlying principle of epidemiology?
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Disease is not randomly distributed in a population
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What are the five objectives of epidemiology (as listed in the textbook)?
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I. Identify cause of disease and risk factors II. Determine the burden of disease in the population III. Describe the natural history of disease IV. Evaluate prevention programs V. Provide research evidence for public policy and legislation
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What are non-modifiable risk factors also called? Name two.
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Intrinsic factors: age, sex, race, genetics,
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Who was the first to dispel superstitious beliefs about diseases and recognized it as a population phenomenon?
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Hippocrates (Occurrence of disease is associated with environmental factors and living habits)
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What was the biggest epidemic disease spread during the Dark Ages and how did it spread?
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The Black Plague. Rats & Fleas./ By Ship
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Who determined that citrus fruits were beneficial for preventing scurvy?
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James Lind (experimental methods)
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1Who did the first vaccination experiment?
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Edward Jenner (use vaccination to prevent disease onset)
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Who examined the cholera epidemic in England by going from house-to-house to determine who was infected and who was not?
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John Snow (Shoe-leather Epidemiology, used observational data to fit experimental methods)
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Who is known as the "father of medicine"?
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Hippocrates
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Who is known as the "father of epidemiology"?
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Girolamo Frascatoro (first notion of communicability of disease)
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Who wrote De Contagione, a book describing the contagionistic theory?
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Girolamo Frascatoro
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Who used death certificates known as the "Bills of Mortality" to develop the first life tables?
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John Graunt (nonrandom distribution of events in population and acute vs chronic disease)
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What does shoe-leather epidemiology mean?
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(Walking/ 'going door to door and doing health surveys',gathering information for epidemiologic studies by directly questioning/inquiry among the people)
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Which bacteriologist formed postulates on rules for causality?
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Robert Koch
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Who wrote an occupational book on miner's diseases?
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Paracelsus (specific exposures result in specific diseases)
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What is the formula for calculating attack rates? What is it useful for?
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# at risk who are sick -------------------------------- Total number at risk
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What is the formula for calculating attack rate ratios?
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Attack Rate in Exposed/Attack Rate in unexposed.
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What does an attack rate ratio of "1" indicate?
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No association
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22. What are the three parts of the Epidemiologic Triad?
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Host-Agent-Environment
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Which part is the primary cause of disease, that is, without it disease cannot occur?
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Agent
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Give an example of a nutritive agent.
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Vitamin C (scurvy) Protein (kwashiorkor) Calories (obesity, anorexia)
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Give an example of a genetic factor for disease.
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-Trisomy 21 - Down's Syndrome -Clotting factor absent (Factor VIII or Factor IX) - hemophilia
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Give an example of an endogenous chemical agent.
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-Endogenous (pituitary hormone/dwarfism,gigantism, growth hormone/acromegaly) -Exogenous (nicotine, alcohol)
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What is the difference between metazoa and protozoa agents?
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-Protozoa (single cell, e.g. malaria, amebiasis) -Metazoa (multi-cellular, e.g. intestinal worms such as nematodes, helminthes)
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Give examples of a bacterial, viral, fungal, and rickettsial agents.
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-Bacterial - meningicocci, shigella, bacillus -Viral - rotaviruses, ebola, eastern equine encephalitis -Fungal- cryptococcosis, coccidioidomycosis -Rickettsial - Rickettsia typhi, Rickettsia rickettsii
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Fatigue is an example of which part of the Epidemiologic Triad?
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Host
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What is the difference between active immunology and passive immunology? Give examples of each.
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Active immunity occurs when a host is exposed to a pathogen and develops the disease, with resulting response from immune system (e,g, antibody response, inflammatory response, lymphocytes). Vaccination can also trigger active immunity. Passive immunity when host receives immune factor from mother during pregnancy or is injected with antibodies to provide short-term immunity e.g. rabies or hepB gamma globulin)
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The density of the population is largest around urban areas. What kind of factor is this?
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Environmental
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What are the three modes of disease transmission?
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1.) Direct (person-to-person) 2.) Airborne (measles) 3.) Indirect Vehicle-borne (most foodborne illnesses) Vector-borne (Rocky mountain spotted fever - tick)
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Sexual contact is a form of which mode of transmission?
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Direct
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Eating eggs with salmonella is a form of which mode of transmission?
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Indirect- vehicle borne
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What is the difference between direct transmission and airborne transmission?
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The case does not have to be present or in contact with the susceptible person. The exposure may occur later, when a susceptible person enters the area or when aerosols move by air current into an area with susceptible present. Direct - case and susceptible both present Airborne - case need not be present for susceptible to be exposed.
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Name a disease that is transmitted by arthropods? What kind of transmission is this called?
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Indirect - Vector borne Malaria - vector borne (mosquitoes) Lyme disease - vector borne (ticks) Plague - vector borne (fleas)
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What are fomites?
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any inanimate object (as a towel or money or clothing or dishes or books or toys etc.) that can transmit infectious agents from one person to another
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38. Give an example of a disease whose human portal of entry is through the skin
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-Anthrax (Bacillus anthracis) -Staph infection (Staphylococcus aureus) -Screw worm (Cochliomyia hominivorax) -Athlete's Foot (Tinea pedis)
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What is a reservoir of infection?
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Any person, animal, arthropod, plant, soil, or substance, or a combination of these, in which an infectious agent normally lives and multiplies, on which it depends primarily for survival, and where it reproduces itself in such a manner that it can be transmitted to a susceptible host, or, the natural habitat of an infectious agent.
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What is the reservoir for rabies? What is the reservoir for athlete's foot?
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Rabies- In the United States, several distinct rabies virus variants have been identified in terrestrial mammals, including raccoons, skunks, foxes, and coyotes. In addition to these terrestrial reservoirs, several species of insectivorous bats are also reservoirs for rabies. Athletes Foot- Humans
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Infectivity
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Infectivity describes the ability of an agent to enter, survive, and multiply in a host: Infectivity = (# Infected / # exposed) x 100
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Pathogenicity
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Describes the ability of an agent to produce clinical disease in a host Pathogenicity = (# with clinical disease / # infected) x 100
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Virulence
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Describes the ability of the agent to cause severe disease Virulence = # deaths from disease / # clinical cases of disease
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Does measles have high or low infectivity? High or low pathogenicity? High or low virulence?
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High, High, Low (in this country, moderate to high in the 3rd world)
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Does rabies have high or low infectivity? High or low pathogenicity? High or low virulence?
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Low to Moderate infectivity High pathogenicity High virulence
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With what measure can we calculate the virulence of a disease?
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Cases Fatality Rate (proportion) = (# deaths from disease/# clinical cases of that disease)
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What defines an epidemic?
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O/E >1 Number of cases observed exceeds the number expected in that time frame and population
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What is another word for an outbreak?
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Epidemic
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What is an incubation period?
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The time between infection of the host and the onset of disease symptoms
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What is the communicable period?
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The communicable period is the time frame during which it is possible of a case of disease to pass the disease to others.
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What are two control measures we use when dealing with people during the communicable period of their disease?
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Isolation, infection control measures like masking of case and hand washing.
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What is herd immunity? What is the magic number to determine herd immunity of a disease?
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Herd immunity is the protection a population or group has from disease when a specific percentage of the group is immune to the disease There is no specific magic number of immunes in a population that results in herd immunity. The number requiring immunity depends on the disease and population you are working with.
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Does association imply causation? Give an example of why or why not?
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No
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Does causation imply association? Give an example of why or why not?
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Causation does imply association. While not all things associated with a disease cause it, anything that causes disease is always associated with being a case. For example, immune suppression is associated with increased likelihood of catching many diseases, including the common cold. However it is the cold virus that causes the cold. One of the cold causing viruses must always be present for a person to catch a cold. The cold virus is therefore associated to catching a cold AND causal.
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What are the two components for causality? Define these two components.
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Necessary causes - if a necessary cause is absent, the disease cannot occur. Sufficient causes - if a sufficient cause is present, the disease always occurs.
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Is smoking a sufficient cause for lung cancer? Why or why not?
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Yes, smoking is a sufficient cause for lung cancer, as no other exposure is needed to cause it.
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What are the nine criteria for determining whether an association is causal?
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1.- Temporal relationship- Exposure must come before disease onset 2.- Strength of the association- Risk ratio or odds ratio 3.- Dose- response relationship- Increasing exposure->Increasing risk of disease 4.- Replication of the findings- Association is replicated in studies in different settings using different methods 5.- Biologic plausibility- Requires knowledge of the biologic etiology of the disease 6.- Alternate explanations eliminated- If knowledge exists, rule out confounding causes 7.- Cessation of exposure- Elimination/ reduction of exposure-> decline in the risk of disease 8.- Specificity of association- WEAKEST, Specific exposure is associated with only 1 disease 9.- Consistency with other knowledge- If relationship is causal, findings should be consistent with other data, existing theory, and knowlege
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Which of the nine criteria is interested in the time occurrence of exposure relative to disease?
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Temporal Ambiguity
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If there is a positive association between numbers of cheeseburgers eaten and increased risk of heart disease, what is this relationship known as?
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Dose Response Relationship
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If the association between radon gas and cancer is found in different kinds of studies (cohort, case-control, cross-sectional) in different countries of the world, which criteria does this fulfill?
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Replication of findings
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Which of the nine criteria is the weakest one and may possibly be eliminated from the list?
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Specificity of association
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Give reasons why it was relatively easy to show that smoking was a cause of lung cancer.
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-Exposure occurred years before disease -Lung cancer incidence in smokers is much greater than in nonsmokers.
