Principles of Epidemiology
A reservoir of an infectious agent can be: An asymptomatic human A symptomatic human An animal The environment
A, B, C, D. An asymptomatic human, a symptomatic human, an animal, the environment A reservoir of an infectious agent is the habitat in which an agent normally lives, grows, and multiplies, which may include humans, animals, and the environment.
For the cruise ship scenario described in Question 7, if you suspected that the norovirus may have been transmitted by ice made or served aboard ship, how might you display "place"? Spot map by assigned dinner seating location Spot map by cabin Shaded map of United States by state of residence Shaded map by whether passenger consumed ship's ice or not
A, B, C. Spot map by assigned dinner seating location, Spot map by cabin, Shaded map of United States by state of residence "Place" includes location of actual or suspected exposure as well as location of residence, work, school, and the like.
John Snow's investigation of cholera is considered a model for epidemiologic field investigations because it included a: Biologically plausible hypothesis Comparison of a health outcome among exposed and unexposed groups Multivariate statistical model Spot map Recommendation for public health action
A, B, D, E. Biologically plausible hypothesis, Comparison of a health outcome among exposed and unexposed groups, Spot map, Recommendation for public health action John Snow's investigation of cholera is considered a model for epidemiologic field investigations because it included a biologically plausible (but not popular at the time) hypothesis that cholera was water-borne, a spot map, a comparison of a health outcome (death) among exposed and unexposed groups, and a recommendation for public health action. Snow's elegant work predated multivariate analysis by 100 years.
In the definition of epidemiology, "determinants" generally includes: Agents Causes Control measures Risk factors Sources
A, B, D, E. agents, causes, risk factors, sources In the definition of epidemiology, "determinants" generally includes the causes (including agents), risk factors (including exposure to sources), and modes of transmission, but does not include the resulting public health action
Disease control measures are generally directed at which of the following? Eliminating the reservoir Eliminating the vector Eliminating the host Interrupting mode of transmission Reducing host susceptibility
A, B, D, E. eliminating the reservoir, eliminating the vector, interrupting mode of transmission, reducing host susceptibility Disease control measures are generally directed at eliminating the reservoir or vector, interrupting transmission, or protecting (but not eliminating!) the host.
Epidemiology, as defined in this lesson, would include which of the following activities? Describing the demographic characteristics of persons with acute aflatoxin poisoning in District A Prescribing an antibiotic to treat a patient with community-acquired methicillin-resistantStaphylococcus aureus infection Comparing the family history, amount of exercise, and eating habits of those with and without newly diagnosed diabetes Recommending that a restaurant be closed after implicating it as the source of a hepatitis A outbreak
A, C, D. Describing the demographic characteristics of persons with acute aflatoxin poisoning in District A. Comparing the family history, amount of exercise, and eating habits of those with and without newly diagnosed diabetes. Recommending that a restaurant be closed after implicating it as the source of a hepatitis A outbreak. Epidemiology includes assessment of the distribution (including describing demographic characteristics of an affected population), determinants (including a study of possible risk factors), and the application to control health problems (such as closing a restaurant). It does not generally include the actual treatment of individuals, which is the responsibility of health-care providers
A key feature of a cross-sectional study is that: It usually provides information on prevalence rather than incidence It is limited to health exposures and behaviors rather than health outcomes It is more useful for descriptive epidemiology than it is for analytic epidemiology It is synonymous with survey
A, C, D. It usually provides information on prevalence rather than incidence. It is more useful for descriptive epidemiology than it is for analytic epidemiology. It is synonymous with survey. A cross-sectional study or survey provides a snapshot of the health of a population, so it assesses prevalence rather than incidence. As a result, it is not as useful as a cohort or case-control study for analytic epidemiology. However, a cross-sectional study can easily measure prevalence of exposures and outcomes.
Which variables might you include in characterizing the outbreak described in Question 7 by person? Age of passenger Detailed food history (what person ate) while aboard ship Status as passenger or crew Symptoms
A, C. Age of passenger, Status as passenger or crew "Person" refers to demographic characteristics. It generally does not include clinical features characteristics or exposures.
A specific case definition is one that: Is likely to include only (or mostly) true cases Is considered "loose" or "broad" Will include more cases than a sensitive case definition May exclude mild cases
A, D. Is likely to include only (or mostly) true cases, May exclude mild cases A specific or tight case definition is one that is likely to include only (or mostly) true cases, but at the expense of excluding milder or atypical cases
A study in which children are randomly assigned to receive either a newly formulated vaccine or the currently available vaccine, and are followed to monitor for side effects and effectiveness of each vaccine, is an example of which type of study? Experimental Observational Cohort Case-control Clinical trial
A, E. Experimental, Clinical trial A study in which subjects are randomized into two intervention groups and monitored to identify health outcomes is a clinical trial, which is type of experimental study. It is not a cohort study, because that term is limited to observational studies.
In the definition of epidemiology, "distribution" refers to? Who When Where Why
A,B,C who, when, where in the definition of epidemiology, "distribution" refers to descriptive epidemiology, while "determinants" refers to analytic epidemiology. So "distribution" covers time (when), place (where), and person (who), whereas "determinants" covers causes, risk factors, modes of transmission (why and how).
The hallmark feature of an analytic epidemiologic study is: (Choose one best answer) Use of an appropriate comparison group Laboratory confirmation of the diagnosis Publication in a peer-reviewed journal Statistical analysis using logistic regression
A. Use of an appropriate comparison group The hallmark feature of an analytic epidemiologic study is use of an appropriate comparison group.
The epidemiologic triad of disease causation refers to: (Choose one best answer) Agent, host, environment Time, place, person Source, mode of transmission, susceptible host John Snow, Robert Koch, Kenneth Rothman
A. agent, host, environment The epidemiologic triad of disease causation refers to agent-host-environment.
A number of passengers on a cruise ship from Puerto Rico to the Panama Canal have recently developed a gastrointestinal illness compatible with norovirus (formerly called Norwalk-like virus). Testing for norovirus is not readily available in any nearby island, and the test takes several days even where available. Assuming you are the epidemiologist called on to board the ship and investigate this possible outbreak, your case definition should include, at a minimum: (Choose one best answer) Clinical criteria, plus specification of time, place, and person Clinical features, plus the exposure(s) you most suspect Suspect cases The nationally agreed standard case definition for disease reporting
A. Clinical criteria, plus specification of time, place, and person A case definition for a field investigation should include clinical criteria, plus specification of time, place, and person. The case definition should be independent of the exposure you wish to evaluate. Depending on the availability of laboratory confirmation, certainty of diagnosis, and other factors, a case definition may or may not be developed for suspect cases. The nationally agreed standard case definition for disease reporting is usually quite specific, and usually does not include suspect or possible cases.
Which term best describes the pattern of occurrence of the three diseases noted below in a single area? Endemic Outbreak Pandemic Sporadic ____ Disease 1: usually 40-50 cases per week; last week, 48 cases ____ Disease 2: fewer than 10 cases per year; last week, 1 case ____ Disease 3: usually no more than 2-4 cases per week; last week, 13 cases
A. Endemic - Disease 1: usually 40-50 cases per week; last week, 48 cases D. Sporadic - Disease 2: fewer than 10 cases per year; last week, 1 case B. Outbreak - Disease 3: usually no more than 2-4 cases per week; last week, 13 cases
A cohort study differs from a case-control study in that: Subjects are enrolled or categorized on the basis of their exposure status in a cohort study but not in a case-control study Subjects are asked about their exposure status in a cohort study but not in a case-control study Cohort studies require many years to conduct, but case-control studies do not Cohort studies are conducted to investigate chronic diseases, case-control studies are used for infectious diseases
A. Subjects are enrolled or categorized on the basis of their exposure status in a cohort study but not in a case-control study The key difference between a cohort and case-control study is that, in a cohort study, subjects are enrolled on the basis of their exposure, whereas in a case-control study subjects are enrolled on the basis of whether they have the disease of interest or not. Both types of studies assess exposure and disease status. While some cohort studies have been conducted over several years, others, particularly those that are outbreak-related, have been conducted in days. Either type of study can be used to study a wide array of health problems, including infectious and non-infectious.
Public health surveillance includes which of the following activities: Diagnosing whether a case of encephalitis is actually due to West Nile virus infection Soliciting case reports of persons with symptoms compatible with SARs from local hospitals Creating graphs of the number of dog bites by week and neighborhood Writing a report on trends in seat belt use to share with the state legislature Disseminating educational materials about ways people can reduce their risk of Lyme disease
B, C, D. Soliciting case reports of persons with symptoms compatible with SARs from local hospitals. Creating graphs of the number of dog bites by week and neighborhood. Writing a report on trends in seat belt use to share with the state legislature. Public health surveillance includes collection (B), analysis (C), and dissemination (D) of public health information to help guide public health decision making and action, but it does not include individual clinical diagnosis, nor does it include the actual public health actions that are developed based on the information.
Indirect transmission includes which of the following? Droplet spread Mosquito-borne Foodborne Doorknobs or toilet seats
B, C, D. mosquito borne, foodborne, doorknobs or toilet seats Indirect transmission refers to the transmission of an infectious agent by suspended airborne particles, inanimate objects (vehicles, food, water) or living intermediaries (vectors such as mosquitoes). Droplet spread is generally considered short-distance direct transmission.
For each of the following, identify the appropriate letter from the time line in Figure 1.27 representing the natural history of disease. Figure 1.27 Natural History of Disease Timeline Match the occurrence to the appropriate stage. Image Description ____ Onset of symptoms ____ Usual time of diagnosis ____ Exposure
C. Onset of symptoms D. Usual time of diagnosis A. Exposure
The Iowa Women's Health Study, in which researchers enrolled 41,837 women in 1986 and collected exposure and lifestyle information to assess the relationship between these factors and subsequent occurrence of cancer, is an example of which type(s) of study? Experimental Observational Cohort Case-control Clinical trial
B, C. Observational, Cohort A study that assesses (but does not dictate) exposure and follows to document subsequent occurrence of disease is an observational cohort study.
British investigators conducted a study to compare measles-mumps-rubella (MMR) vaccine history among 1,294 children with pervasive development disorder (e.g., autism and Asperger's syndrome) and 4,469 children without such disorders. (They found no association.) This is an example of which type(s) of study? Experimental Observational Cohort Case-control Clinical trial
B, D. Observational, Case-control A study in which subjects are enrolled on the basis of having or not having a health outcome is an observational case-control study
For the cruise ship scenario described in Question 7, how would you display the time course of the outbreak? (Choose one best answer) Endemic curve Epidemic curve Seasonal trend Secular trend
B. Epidemic curve An epidemic curve, with date or time of onset on its x-axis and number of cases on the y-axis, is the classic graph for displaying the time course of an epidemic
Comparing numbers and rates of illness in a community, rates are preferred for: (Choose one best answer) Conducting surveillance for communicable diseases Deciding how many doses of immune globulin are needed Estimating subgroups at highest risk Telling physicians which strain of influenza is most prevalent
C. Estimating subgroups at highest risk Rates assess risk. Numbers are generally preferred for identifying individual cases and for resource planning
When analyzing surveillance data by age, which of the following age groups is preferred? (Choose one best answer) 1-year age groups 5-year age groups 10-year age groups Depends on the disease
D. Depends on the disease Epidemiologists tailor descriptive epidemiology to best describe the data they have. Because different diseases have different age distributions, epidemiologists use different age breakdowns appropriate for the disease of interest
A propagated epidemic is usually the result of what type of exposure? Point source Continuous common source Intermittent common source Person-to-person
D. Person to person A propagated epidemic is one in which infection spreads from person to person.
