epidemiology
For the cruise ship scenario described in Question 7, how would you display the time course of the outbreak? (Choose one best answer)
B. 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.
Disease control measures can be directed at the:
A, B, C, D, E. Disease control measures can be directed at the eliminating the agent (e.g., by sterilizing surgical equipment), interrupting transmission (e.g., reducing mosquito population, covering one's mouth when coughing), preventing entry into a host (e.g., wearing a mask, using insect repellant), or improving host defenses (e.g., by immunization).
A reservoir of an infectious agent can be:
A, B, C, D. 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.
Epidemiology, as defined in this lesson, would include which of the following activities?
A, C, D. 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.
Which variables might you include in characterizing the outbreak described in Question 7 by person?
A, C. "Person" refers to demographic characteristics. It generally does not include clinical features characteristics or exposures.
A specific case definition is one that:
A, D. 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.
If a particular outbreak presents an unusual opportunity to learn more about the disease and its epidemiology by conducting a study, but early disease control measures would interfere with the study, one should conduct the study quickly, then implement control measures immediately afterwards.
B (False). The most important public health reason for investigating an outbreak is disease control and prevention. Protecting and promoting the public's health is our primary mission, even if it interferes with our ability to conduct research.
What term refers to "an occurence of an illness or illness in a population"?
Morbidity
What term refers to "the occurrence of death from a condition in a population?" A) Morbidity B)Mortality C) Prevalence D) Incidence
Mortality
Approximately 400,000 Americans today have ever been diagnosed with lung cancer. This is also known as ______.
Prevalence
An exposure associated with a disease is known as:
Risk Factor
Ideally, a case definition is 100% accurate in identifying who does and does not have the disease in question, but in reality few case definitions achieve this ideal.
A (True). A case definition is a decision making tool. It provides criteria for classifying illness as a "case" or "not a case. " However, few case definitions are 100% accurate, because people with mild or atypical or asymptomatic disease are likely to be missed, and people with similar but not the same disease may be included. Even a case definition that requires a laboratory test is not 100% perfect, because laboratory tests themselves are not perfect.
Vital statistics are important sources of data on which of the following?
A (True). Vital statistics are usually thought of as an archive of births, deaths, marriages, and divorces. Vital statistics offices in health departments typically are not linked to disease prevention and control activities. However, surveillance for certain health problems might rely on vital statistics as its primary source of data. When these data undergo timely and systematic analysis, interpretation, and dissemination with the intent of influencing public health decision-making and action, they become surveillance data.
Which of the following may be useful in generating hypotheses in an outbreak setting?
A, B, C, D, E, F. Hypotheses can be generated in a variety of ways. One way is based on subject matter knowledge derived by reviewing the literature or talking with experts - what are the usual causes, sources, vehicles, or modes of transmission? Other ways include reviewing the overall pattern and the outliers from the descriptive epidemiology, by asking case-patients if they have any suspicions about the cause of their illness, and by asking the same question of local authorities (if you are from out of town).
A case report form devised for an outbreak investigation usually includes which of the following types of information?
A, B, C, D, E. A data collection form for an outbreak investigation should include patient identifying information (e.g., name, telephone number), demographic information (e.g., age, sex), clinical information (e.g., date of onset, laboratory confirmation, whether hospitalized), risk factor information (disease-specific, e.g., attended sports banquet (yes/no), previously vaccinated?), and information about who collected the data (e.g., interviewer or abstracter initials, date of collection).
Possible explanations for a case that occurs substantially later than the other cases in an outbreak include:
A, B, C, D, E. A late case on an epidemic curve has several possible explanations, including a case of a similar but unrelated disease, a secondary case (assuming it occurs one incubation period after another case), a case with an unusually long incubation period, a case that resulted from exposure at a different time (for example, someone who ate leftovers the next day), or an error in recall or in recording the date.
Routine analysis of notifiable disease surveillance data at the state health department might include looking at the number of cases of a disease reported this week ...
A, B, C, D, E. An increase in case reports during a single week might represent a true increase in disease (i.e., an outbreak). However, the increase can also represent an increase in the population (e.g., from an influx of tourists, migrant workers, refugees, or students); reporting of cases in a batch, particularly after a holiday season; duplicate reports of the same case; laboratory or computer error; a new clinic or health-care provider that is more likely to make a particular diagnosis or is more conscientious about reporting; or other sudden changes in the method of conducting surveillance.
Current public health surveillance targets which of the following?
A, B, C, D, E. Current public health surveillance targets health-related conditions among humans, including chronic diseases (e.g., cancer), communicable diseases (e.g., those on the notifiable disease list), health-related behaviors, and occupationally related conditions (e.g., black lung disease and other pneumoconioses). Surveillance also focuses on indicators of disease potential (e.g., such diseases among animals as rabies) or presence of an infectious agent among animals or insects (e.g., West Nile virus among mosquitoes).
A case definition during an outbreak investigation should specify:
A, B, C, D. A case definition for an outbreak should specify clinical criteria as well as appropriate time, place, and person characteristics. The case definition should NOT include the hypothesized exposure of interest. First, the hypothesized exposure may not turn out to be the true exposure, so inclusion of the hypothesized exposure as part of the case definition during the case-finding step may result in missed cases. Second, during the analytic step, disease status and exposure must be determined independently to avoid bias. Including exposure as part of the case definition means that all cases will, by definition, be exposed, while only some of the controls will likely be exposed. As a result, the exposure will appear to be associated with disease, not necessarily because it is the true exposure, but because of the case definition.
Public health surveillance is only conducted by public health agencies.
A, B, C, D. Among the uses of surveillance are detecting individual cases of diseases of public health importance (e.g., malaria), supporting planning (e.g., priority setting), monitoring trends and patterns of health-related conditions (e.g., elevated blood lead levels), and supporting evaluation of prevention and control measures (e.g., a vaccination requirement).
Factors that influence a health department's decision whether or not to conduct a field investigation in response to one or more cases of disease include:
A, B, C, D. Factors influencing a health department's decision to conduct a field investigation include some related to the health problem itself (e.g., severity of illness, number of cases, availability of prevention / control measures), some relate to the health department (e.g., "corporate culture" for conducting field investigations versus handling it by telephone, available staff and resources), and some relate to external concerns (e.g., public or political pressure).
The best measure of association to use for these data is a/an:
A, B, C, D. The fraction 50 ⁄ 53 (see top row of table) is the proportion of wedding cake eaters who became ill, which is a food-specific attack rate. A food-specific attack rate is a type of attack rate, which in turn is synonymous with incidence proportion.
As described in this lesson, public health surveillance includes which activities?
A, B, C, D. The term public health surveillance includes data collection, analysis, interpretation, and dissemination to help guide health officials and programs in directing and conducting disease control and prevention activities. However, surveillance does not include control or prevention activities themselves.
Common methods of identifying additional cases (expanding surveillance) as part of an outbreak investigation include:
A, B, C, D. To identify additional cases as part of an outbreak investigation, health department staff contact (by telephone, broadcast fax, or e-mail) physicians' offices, clinics, hospitals, and laboratories. Depending on the affected age group, staff might also contact day care centers, schools, employers, or nursing homes. Sometimes a press release is issued to local media outlets that inform the public and suggest that persons with particular symptoms or exposures contact their healthcare providers or health department. In addition, health department staff routinely interview case-patients and ask whether they know any persons with the same exposure, if known, or with the same illness.
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"?
A, B, C. "Place" includes location of actual or suspected exposure as well as location of residence, work, school, and the like.
Evaluating and improving surveillance should address which of the following?
A, B, D. The incidence of, public concern about, and social and economic impact of a health problem are all important in assessing its suitability for surveillance. Although previous studies of the problem might have helped to characterize its natural history, cause, and impact, the number of such studies is not used as a criterion for prioritization.
A spot map is particularly useful for displaying:
A, B. A spot map is useful for pinpointing the geographic location of exposures, residences, employment sites, and the like. The spots represent occurrences, either of exposure or disease. Spot maps are not used to display rates. Rather, area maps (also called shaded or chloropleth maps) are used to display incidence and prevalence rates.
All proportions are ratios, but not all ratios are proportions.
A, B. All fractions are ratios. This fraction is also a proportion, because all of the deaths from lung cancer in the numerator are included in the denominator. It is not an incidence proportion, because the denominator is not the size of the population at the start of the period. It is not a mortality rate because the denominator is not the estimated midpoint population.
A key feature of a cross-sectional study is that:
A, C, D. 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.
Common uses and applications of public health surveillance include which of the following?
A, C, D. Data collected through vital registration, disease notifications, and population surveys are commonly used for surveillance of health-related problems. Data from randomized clinical trials typically cover only a specially selected population and are used to answer specific questions about the effectiveness of a particular treatment. They are not useful for surveillance.
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?
A, E. 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.
The case definition used for surveillance of a health problem should be the same as the case definition used for clinical (treatment) purposes.
B (False). A case definition for surveillance should be clear, understandable, acceptable, and implementable by those who are required to apply it. However, it need not use the same criteria that are used for clinical purposes. For example, health-care providers might treat patients on the basis of clinical features without laboratory confirmation, whereas a surveillance case definition might require confirmation, or vice versa.
Descriptive epidemiology is essential for "characterizing the outbreak" by time, place, and person, but has little bearing on the analytic epidemiology.
B (False). Descriptive epidemiology is essential not only for characterizing the pattern and distribution of the outbreak, but also for generating testable hypotheses about the source, mode of transmission, and risk factors for illness. Two of the suggested ways for generating hypotheses are to review the descriptive epidemiology, particularly (1) the overall pattern of cases and develop hypotheses about what they have in common, and (2) the outliers to determine how they might be linked to the other cases. These hypotheses, in turn, are the ones that are tested using analytic epidemiology.
Key sources of morbidity data include which of the following?
B (False). Notifiable disease surveillance targets occurrence or death from any of the diseases on the list.
Once a case definition for an outbreak investigation has been established, it should not be changed.
B (False). On the one hand, case definitions need to be applied consistently, so that everyone involved in an investigation defines a case in the same way. On the other hand, case definitions can change during the course of an outbreak. For example, for case finding purposes, a case definition might include categories such as confirmed, probable, and possible, to try to include as many cases as possible. Later on, in the analytic phase, the case definition may be restricted to the confirmed cases. As another example, a case definition may initially be restricted to a particular community. If the outbreak spreads beyond that geographic area, the "place" component of the case definition also would need to be expanded.
Data collected through which of the following methods is commonly used for surveillance?
B (False). One of the important uses of surveillance data and one of the key reasons to close the surveillance loop by disseminating surveillance data back to health-care providers, is to provide clinically relevant information about disease occurrence, trends, and patterns. For example, health departments alert clinicians to the presence of new diseases (e.g., severe acute respiratory syndrome [SARS]) and provide information so that clinicians can make diagnoses. Health departments also advise clinicians about changing patterns of antibiotic resistance so that clinicians can choose the right treatment regimen.
To avoid skipping a critical step, investigators should conduct the steps of an outbreak investigation in the precise order you answered in Question 5.
B (False). The order presented in this text is conceptual. In practice, the order can be different. For example, preparing for field work often follows establishing the existence of an outbreak and verifying the diagnosis. When possible, control measures are initiated at the same time the field investigation begins, or even earlier.
Public health surveillance can be described primarily as which of the following?
B (False). The practice of surveillance is not limited to public health agencies. Hospitals, nursing homes, the military, and other institutions have long conducted surveillance of their populations.
Underreporting is not a problem for detecting outbreaks of notifiable diseases because the proportion of cases reported tends to remain relatively stable over time.
B (False). Underreporting is a serious problem for surveillance that relies on notifications. Because the notifiable disease surveillance is supposed to identify individual cases of disease of public health importance, underreporting of even a single case of, for example, hepatitis A in a food handler, can result in an outbreak that should have been prevented. Similarly, if a limited number of cases are reported at all, even outbreaks can be missed.
Public health surveillance includes which of the following activities:
B, C, D. 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.
Vital statistics provide an archive of certain health data. These data do not become surveillance data until they are analyzed, interpreted, and disseminated with the intent of influencing public health decision-making or action.
B, C, D. Sources of morbidity (illness) data include notifiable disease reports, laboratory data, hospital discharge data, outpatient health-care data, and surveillance for specific conditions (e.g., cancer). Vital records are an important source of mortality data, and even though a patient first gets sick from a disease before dying from it, vital records are not regarded as a source of data for the surveillance of morbidity from the disease. Environmental monitoring is used to evaluate disease potential or risk.
The fraction 54 ⁄ 79 is a/an:
B, C, D. The fraction 54 ⁄ 79 (see bottom row of the table) reflects the overall attack rate among persons who attended the wedding and were interviewed. Attack rate is a synonym for incidence proportion.
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?
B, C. A study that assesses (but does not dictate) exposure and follows to document subsequent occurrence of disease is an observational cohort study.
Why should an investigator who has no clinical background nonetheless talk to a patient or two as an early step in the outbreak investigation?
B, C. Even an investigator without a clinical background should, if possible, see and talk to a patient or two to gain a better understanding of the clinical features of the disease (needed for developing a case definition) and to generate hypotheses by asking about possible exposures.
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?
B, D. A study in which subjects are enrolled on the basis of having or not having a health outcome is an observational case-control study.
Initiating surveillance for a public health problem or adding a disease to the notifiable disease list is justified for which of the following reasons?
B, D. Initiating surveillance for a health-related problem can be justified for multiple reasons. These reasons include if a disease is new and surveillance is the most effective means for collecting information on cases to learn more about its clinical and epidemiologic features (e.g., SARS); if a new prevention or control measure is about to be implemented and surveillance is the most effective means for assessing its impact (e.g., varicella vaccination regulations); or if surveillance is needed to guide, monitor, and evaluate prevention or control measures. Surveillance is more difficult to justify if a disease does not occur locally, even if it is a communicable disease with a high case fatality rate (e.g., Ebola or Marburg virus infection), or simply because CDC requests it (without funding).
Use the following choices for Questions 7a-c. Cluster Epidemic Outbreak____ 200 cases of Marburg virus infection in several districts in Angola over several months (usually none)____ 40 cases of Salmonella Enteritidis in 1 week traced to a single meal served at a cafeteria (usually none)____ 10 cases of cancer diagnosed over 2 years among residents of a single neighborhood (previous data not available)
B. Epidemic, the occurrence of more cases of disease than expected in a given area or among a specific group of people over a particular period of time, tends to refer to more widespread occurrence than outbreak. C. Outbreak tends to be used for an increase that is localized. A. Cluster is an aggregation of cases in a given area over a particular period of time that seems unusual or suspicious, but often the usual or expected number of cases is not known.
The primary reason for preparing and distributing periodic surveillance summaries is which of the following?
B. Sensitivity is the ability of surveillance (or laboratory tests or case definitions) to detect a true case (or, for certain systems, a true outbreak). Specificity is the ability of surveillance (or laboratory tests or case definitions) to rule out disease among persons who do not have it.
Notifiable disease surveillance usually focuses on morbidity from the diseases on the list and does not cover mortality from those diseases.
B. The list of nationally notifiable diseases is compiled by the Council of State and Territorial Epidemiologists (CSTE) and the Centers for Disease Control and Prevention. The list of notifiable diseases that physicians must report to their state or local health department is set by the state, either by the state legislature, the state board of health, the state health department, the state health officer, or the state epidemiologist. CSTE votes on the diseases that should be nationally notifiable, but the states have the ultimate authority whether to add any newly voted diseases to their state list.
One week, a state health department received substantially more case reports of a disease in one county than had been reported during the previous 2 weeks. No increase was reported in neighboring counties. Possible explanations for this increase include which of the following?
B. The primary purpose of preparing and distributing surveillance summaries is to provide timely information about disease occurrence to those in the community who need to know. The report also serves to motivate those who report by demonstrating that their efforts are valued and to inform health-care providers and others in the community about health department activities and general public health concerns.
Many of the students at the boarding school, including 6 just coming down with varicella, went home during the Thanksgiving break. About 2 weeks later, 4 siblings of these 6 students (out of a total of 10 siblings) developed varicella. The secondary attack rate among siblings was, therefore,:
B. The secondary attack rate is calculated as the number of cases among contacts (4) divided by the number of contacts (10).
The best estimate of the association between wedding cake and illness is:
C. Investigators were able to interview almost everyone who attended the wedding, so incidence proportions (measure of risk) were calculated. When incidence proportions (risks) can be calculated, the best measure of association to use is the ratio of incidence proportions (risks), i.e., risk ratio.
Comparing numbers and rates of illness in a community, rates are preferred for: (Choose one best answer)
C. Rates assess risk. Numbers are generally preferred for identifying individual cases and for resource planning.
Definition of epidemiology
"the study of the distribution and determinants of disease or health status in a population; the study of the occurrence and causes of health effects in humans".
A state health department decides to strengthen its notifiable disease reporting. The one best action to take is to ...
C. The most important way to improve notifiable disease surveillance is to ensure that everyone who is supposed to report knowsthat they are supposed to report,what to report (i.e., which diseases are on the list), andhow, to whom, and how quickly to report. In addition, they will be more likely to report if they know that the health department is actually doing something with the reports. No data are available that demonstrate that reporting through the Internet improves reporting; in fact, for certain health-care providers, reporting might involve extra work. Requiring more disease-specific forms tends to reduce reporting, because it requires more time and effort for those reporting. Reducing the number of diseases on the list might be part of a strategy to improve reporting, but it is not the most important way to do so.
An urban area has had a large migration over the past 10 years of younger individuals to other areas in order to look for better opportunities. This high mobility in the population is an example of what kind of descriptive variable?
Community Infrastructure
Environmental epidemiology
Environmental epidemiology is concerned with environmental conditions or hazards that may pose a health risk to populations.1 For example, epidemiologists may investigate a cancer cluster in a particular community, or question whether people with a particular disease have higher levels of exposure than people without the disease.
how did epidemiology start
Epidemiology originates from Hippocrates' observation more than 2000 years ago that environmental factors influence the occurrence of disease
A community agency is putting together an exercise program for senior women to help in the prevention of osteoporosis. This would be an example of:
Primary prevention
What component of Hill's Aspects of Association asks if people are developing the same disease condition after exposure?
Specificity
An example of active prevention of disease is?
Using a seat belt while riding in a vehicle
n the definition of epidemiology, "distribution" refers to:
When
Which of the following are frequency measures?
requency measures of health and disease include those related to birth, death, and morbidity (incidence and prevalence).
An industrial town along the shore of Lake Michigan is known for having poor air quality due to factories and shipping industry near residential areas. This would be an example of what kind of descriptive variable?
Environmental
The epidemiologic triad of disease causation refers to: (Choose one best answer)
A. The epidemiologic triad of disease causation refers to agent-host-environment.
The list of diseases that a physician must report to the local health department is typically compiled by the...
A or B, depending on the state. The agency that a physician should notify is determined by the state, just as the list of notifiable diseases is set by the state (see answer to question 12). The manner in which notification should occur and how rapidly reports should be made are also defined by the state and can vary by disease. For example, the state might require that a case of cholera be reported immediately by telephone or fax to the local or state health department, whereas reporting of varicella (chickenpox) might only be required monthly, by using a paper form. Regardless of the disease and reporting requirements, reporting should proceed through established channels. In certain states, physicians should notify the county health department, which will then notify the state health department, which will notify CDC, which will notify the World Health Organization. In states with no or limited local health departments, physicians are usually required to notify the state health department. The seriousness of the disease might influence how rapidly these communications take place but should not influence the sequence.
In the definition of epidemiology, "distribution" refers to:
A, B, C. 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).
Use the following choices for Questions 17a-d.
A, B, D, E. Analysis by time often includes comparison with previous weeks and previous years. Analysis by place can include analysis of both numbers and rates. Routine analysis by person includes age and sex, but a three-variable table of age by race and sex is probably too much stratification for routine analysis.
In the definition of epidemiology, "determinants" generally includes:
A, B, D, E. 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.
John Snow's investigation of cholera is considered a model for epidemiologic field investigations because it included a:
A, B, D, E. 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.
Use the following choices for Questions 14a-e.
A, B, D. Evaluation of surveillance for a health-related problem should include review of the purpose and objectives of surveillance, the resources needed to conduct surveillance for the problem, and whether the characteristics of well-conducted surveillance are present. Because surveillance does not have direct responsibility for the control of the health problem, this is not part of evaluating a surveillance system. Whether effective measures for preventing or controlling a health-related problem are available can be a useful criterion in prioritizing diseases for surveillance.
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)
A. 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.
In a state that did not require varicella (chickenpox) vaccination, a boarding school experienced a prolonged outbreak of varicella among its students that began in September and continued through December. To calculate the probability or risk of illness among the students, which denominator would you use?
A. All fractions, including proportions, are ratios. But only ratios in which the numerator is included in the denominator is a proportions.
Use the following choices for Questions 14a-c.
A. As in Answer 3, our primary mission is to protect the public's health, so disease control and prevention measures should take priority whenever possible. Because disease prevention and control measures are often aimed at interrupting transmission, such measures can be implemented if the source and mode of transmission are known.
Use the following choices for Questions 14a-c. Disease control and prevention efforts take priority over investigation efforts Investigation efforts take priority over disease control and prevention efforts____ Outbreak with known causative agent, source, and mode of transmission____ Outbreak with known causative agent, but unknown source and mode of transmission____ Outbreak with unknown causative agent, source, and mode of transmission
A. As in Answer 3, our primary mission is to protect the public's health, so disease control and prevention measures should take priority whenever possible. Because disease prevention and control measures are often aimed at interrupting transmission, such measures can be implemented if the source and mode of transmission are known. B. If the agent is known but the source and mode of transmission are not known (example: Salmonella eventually traced to marijuana), then the health department does not know how to target its intervention. Investigation to learn the source and/or mode is necessary. B. As in Answer 4b, If the agent, source, and mode of transmission are not known (examples: Legionnaires' Disease in Philadelphia in 1976; Kawasaki Syndrome — if it turns out to be an infectious disease), then the health department does not know how to target its intervention. Investigation to learn the source and/or mode is necessary.
A physician working in an emergency room in Town A, USA, has just examined a tourist from Southeast Asia with watery diarrhea. The physician suspects the man might have cholera. The physician should notify the ...
A. Notifiable disease surveillance is state-based, with subsequent reporting to CDC. Surveillance for consumer product-related injuries is hospital emergency department-based with subsequent reporting to the Consumer Product Safety Commission. A. Notifiable disease surveillance attempts to identify every case of a notifiable disease. Surveillance for consumer product-related injuries relies on a sample of hospital emergency departments to characterize the incidence and types of these injuries. C. Because surveillance for notifiable diseases and surveillance for consumer product-related injuries are both ongoing, both can monitor trends over time. B. Surveillance for consumer product-related injuries is based on a statistically valid sample of hospital emergency departments in the United States. Notifiable disease surveillance covers the entire population. D. Neither approach to surveillance is perfect. Underreporting is a serious problem in the majority of states for notifiable disease surveillance. Surveillance for consumer product-related injuries is based on visits to a sample of emergency departments; therefore, persons who do not seek care at an emergency department are not represented.
Use the following choices for Questions 21a-b. Predictive value positive. Sensitivity. Specificity. Validity.
A. Predictive value positive is the proportion of patients (or outbreaks) detected by surveillance who truly have the disease (or are true outbreaks). Predictive value positive is a function of both the sensitivity of surveillance and the prevalence of the disease (or prevalence of real outbreaks).
The hallmark feature of an analytic epidemiologic study is: (Choose one best answer)
A. The hallmark feature of an analytic epidemiologic study is use of an appropriate comparison group.
A cohort study differs from a case-control study in that:
A. 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.
The attributable proportion for wedding cake is:
A. The risk ratio is calculated as the attack rate among cake eaters divided by the attack rate among those who did not eat cake, or (50 ⁄ 53) ⁄ (4 ⁄ 26), or 94.3% ⁄ 15.4%, which equals 6.1.
Health-care providers might be important sources of surveillance data used by public health officials, and they should receive feedback to close the surveillance loop as a courtesy; however, the results almost never have any relevance to patient care provided by those health-care providers.
B. Vital statistics refer to data on birth, death, marriage, and divorce. Therefore, vital statistics are the primary source of data on mortality, but not on morbidity (illness), behaviors, injury (other than fatal injuries), and health-care usage. Before development of population health surveys and disease registries and the use of health-care records to assess morbidity, vital statistics were the primary source of data on the health of populations. During recent years, administrative, financial, and other health-care-related records have supplemented the information from vital statistics, especially for assessing morbidity within populations. National, state, and local population-based health surveys, some of which are conducted on a regular or continuing basis, provide another important part of our view of the health of populations.
Criteria for prioritizing health problems for surveillance include which of the following?
C (Both). Surveillance based on specific case definition for a disease attempts to identify individual cases of disease of public health importance, and syndromic surveillance, depending on its purpose, might also attempt to identify cases of disease of public health importance. In certain situations, the goal of syndromic surveillance might be to identify clusters or outbreaks (more cases than expected) of disease rather than individual cases. C (Both). Both syndromic surveillance and surveillance based on a specific case definition for a disease can be used to watch for diseases caused by acts of biologic or chemical terrorism. Which approach is used depends on the disease and the setting. B. Syndromic surveillance that targets sales of over-the-counter medications, calls to hotlines, and school or work absenteeism all watch for disease before a patient seeks care from a health-care provider. Surveillance based on a specific case definition for a disease is usually based on reporting by a health-care provider. D. Neither type of surveillance can function properly without attention and effort on the part of the health department. Health department staff should review the case report forms and conduct follow-up of cases reported through surveillance based on specific case definitions for diseases. Health department staff should review the cases identified by syndromic surveillance and determine whether they reflect true outbreaks or not. Additionally, health department staff should compile and communicate the results. These tasks are a minimum.
Which are the most common ways that a local health department uncovers outbreaks?
C, D. Most outbreaks come to the attention of health authorities because an alert clinician or a concerned case-patient (or parent of a case-patient) calls. The other methods listed occasionally detect outbreaks, but less frequently.
The units for the quantity you calculated in Question 8 could be expressed as:
C, D. The person-time rate presented in Question 8 should be reported as 5 cases per 250 person-years. Usually person-time rates are expressed per 1,000 or 10,000 or 100,000, depending on the rarity of the disease, so the rate in Question 8 could be expressed as 2 cases per 100 person-years of follow-up. One could express this more colloquially as 2 new cases of eye disease per 100 diabetics per year.
Use the following choices for the characteristics or features listed below:
C, D. The person-time rate presented in Question 8 should be reported as 5 cases per 250 person-years. Usually person-time rates are expressed per 1,000 or 10,000 or 100,000, depending on the rarity of the disease, so the rate in Question 8 could be expressed as 2 cases per 100 person-years of follow-up. One could express this more colloquially as 2 new cases of eye disease per 100 diabetics per year.
Investigators enrolled 100 diabetics without eye disease in a cohort (follow-up) study. The results of the first 3 years were as follows:Year 1: 0 cases of eye disease detected out of 92; 8 lost to follow-upYear 2: 2 new cases of eye disease detected out of 80; 2 had died; 10 lost to follow-upYear 3: 3 new cases of eye disease detected out of 63; 2 more had died; 13 more lost to follow-upThe person-time incidence rate is calculated as:
D. During year 1, 92 returning patients contributed 92 person-years; 8 patients lost to follow-up contributed 8 × ½ or 4 years, for a total of 96. During the second year, 78 disease-free patients contributed 78 person-years, plus ½ years for the 2 with newly diagnosed eye disease, the 2 who had died, and the 10 lost to follow-up (all events are assumed to have occurred randomly during the year, or an average, at the half-year point), for a total of 78 + 14 × ½ years, for another 85 years. During the third year, returning healthy patients contributed 60 years; the 3 with eye disease, the 4 who died, and the 11 lost to follow-up contributed 18 × ½ years or 9 years, for a total of 69 years during the 3rd year. The total person-years is therefore 96 + 85 + 69 = 250 person-years.
Use the following steps of an outbreak investigation for Question 5: Analyze data by time, place, and person Conduct a case-control study Generate hypotheses Conduct active surveillance for additional cases Verify the diagnosis Confirm that the number of cases exceeds the expected number Talk with laboratorians about specimen collection
D. Early steps include confirming that the number of cases exceeds the expected number, verifying the diagnosis, and preparing for field work (which includes talking with laboratorians about specimen collection). Next steps include conducting surveillance to identify additional cases; analyzing the data by time, place, and person; generating hypotheses; and evaluating those hypotheses (for example, by conducting a case-control study).
When analyzing surveillance data by age, which of the following age groups is preferred? (Choose one best answer)
D. 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 group of tourists on a weeklong bus tour of a European country experienced an outbreak of norovirus. The group had followed a consistent meal time pattern: each morning they had breakfast together in whichever hotel they had stayed from 6:00 a.m. to 7:00 a.m., stopped for lunch from 1:00 p.m. to 2:00 p.m., then had dinner together either at the next hotel or at a restaurant at about 7:00 p.m. The incubation period for norovirus is about 24-48 hours, with a median of about 33 hours. On which day and at which meal was exposure most likely?
D. Subtracting 24 hours (the minimum incubation period) from the time of onset of the first case puts you in the April 20 Dinner interval. Subtracting 33 hours from the median case (which occurred in the 4-8 AM interval) on April 22), puts you in the April 20 4-7 pm interval, near both lunch and dinner that day. While the minimum method points to dinner on April 20, thorough investigators would probably investigate possible exposures at lunch that day, too.
Which of the following mortality rates use the estimated total mid-year population as its denominator?
D. The attributable proportion is calculated as the attack rate among cake eaters minus the attack rate among non-eaters, divided by the attack rate among cake eaters, or 94.3 - 15.4) ⁄ 94.3, which equals 83.7%. This attributable proportion means that 83.7% of the illness might be attributable to eating the wedding cake (note that some people got sick without eating cake, so the attributable proportion is not 100%).
The fraction 50 ⁄ 53 is a/an:
D. The fraction 50 ⁄ 54 (under the Ill column) is the proportion of case-patients who ate wedding cake. It is not an attack rate, because the denominator of an attack rate is the size of the population at the start of the period, not all cases.
The key feature of an analytic (epidemiologic) study is: (Select only one answer)
D. The key feature that characterizes an analytic (epidemiologic) study is presence of a comparison group. Single case reports and case series do not have comparison groups and are not analytic studies. Cohort studies (compares disease experience among exposed and unexposed groups) and case-control studies (compares exposure experience among persons with and without disease) have comparison groups and are analytic studies.
