Epidemiology CDC 2019

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 explanation: 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.

For the cruise ship scenario described in Question 7, how would you display the time course of the outbreak?

Epidemic curve explanation: 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

Estimating subgroups at highest risk

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 and Clinical Trial

A specific case definition is one that

Is likely to include only (or mostly) true cases; May exclude mild cases

A key feature of a cross-sectional study is that:

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

Indirect transmission includes which of the following?

Mosquito-borne; Foodborne; Doorknobs or toilet seats explanation: 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.

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?

Observational and Case-control

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?

Observational and Cohort

A propagated epidemic is usually the result of what type of exposure?

Person-to-person explanation: A propagated epidemic is one in which infection spreads from person to person.

Public health surveillance includes which of the following activities:

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

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

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

The hallmark feature of an analytic epidemiologic study is: (Choose one best answer)

Use of an appropriate comparison group explanation: The hallmark feature of an analytic epidemiologic study is use of an appropriate comparison group

In the definition of epidemiology, "distribution" refers to

who, when and where explanation: 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)

Disease control measures are generally directed at which of the following?

Eliminating the reservoir; Eliminating the vector; Interrupting mode of transmission; Reducing host susceptibility

The epidemiologic triad of disease causation refers to

Agent, host, environment

In the definition of epidemiology, "determinants" generally includes

Agents, Causes, Risk Factors, Sources explanation: 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

Which variables might you include in characterizing the outbreak described in Question 7 by person?

Age of passenger and Status as passenger or crew explanation: "Person" refers to demographic characteristics. It generally does not include clinical features characteristics or exposures.

A reservoir of an infectious agent can be:

An asymptomatic human; A symptomatic human; An animal; The environment

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; Spot map; Recommendation for public health action

When analyzing surveillance data by age, which of the following age groups is preferred?

Depends on the disease

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; 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

Endemic

Disease 1: usually 40-50 cases per week; last week, 48 cases

Sporadic

Disease 2: fewer than 10 cases per year; last week, 1 case

Outbreak

Disease 3: usually no more than 2-4 cases per week; last week, 13 cases