Preventive Medicine: Epidemiology 3

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Questions and Answers

What is the primary purpose of disease surveillance?

To promote and safeguard public health (correct)

To develop new treatments for diseases

To investigate the causes of disease outbreaks

To create a system for tracking disease incidence

What is the foundation of disease control efforts?

Public health education

Vaccination programs

Surveillance (correct)

Research and development

What is required for the development of a surveillance system?

Clear objectives regarding the diseases or conditions to be covered (correct)

Funding from external sources

Advanced technology for data analysis

A large team of researchers

What do epidemiologists study to understand patterns of diseases?

The time and geographic location of cases and the characteristics of persons involved Signup and view all the answers

What may be responsible for the observed changes in disease patterns?

Changes in disease detection or reporting practices Signup and view all the answers

What does a long-term increase in a disease in one region suggest?

A more widespread problem Signup and view all the answers

Why do infectious diseases that are spread by the respiratory route have a higher incidence in the winter and early spring?

Because people spend more time indoors, where the air changes slowly Signup and view all the answers

What is the effect of the introduction of varicella vaccine on the seasonal pattern of varicella?

It has eliminated the seasonal pattern Signup and view all the answers

What is the purpose of incorporating seasonal variation into calculations?

To determine the usual number of cases or rates of disease Signup and view all the answers

What is the significance of a long-term trend in disease?

It is usually of greater significance than an outbreak or epidemic Signup and view all the answers

When are most diseases spread by insect or arthropod vectors typically acquired?

Late spring or summer Signup and view all the answers

What is the purpose of using an 'epidemiologic year'?

To put the high-incidence months near the center of a graph Signup and view all the answers

Why does recreational drowning occur more frequently on weekends?

Because more people engage in water recreation on weekends Signup and view all the answers

What is an epidemic?

An unusual frequency of disease Signup and view all the answers

How does the CDC determine when and where influenza and pneumonia outbreaks occur?

By comparing reported deaths to a seasonally adjusted expected percentage Signup and view all the answers

What is the main concern of surveillance for bioterrorism?

Rapid detection of a problem Signup and view all the answers

What makes detection of bioterrorism more difficult?

If the disease is scattered over a wide geographic area Signup and view all the answers

What is the purpose of special surveillance techniques in bioterrorism?

To enable rapid detection of major increases in the most likely biologic agents Signup and view all the answers

What is the primary objective of surveillance in determining the effectiveness of a vaccine program?

To determine whether a vaccine program is effective Signup and view all the answers

What is typically used to define a case of a reportable disease or condition?

Clinical findings, laboratory results, and epidemiologic data Signup and view all the answers

What is the main difference between active and passive surveillance?

Active surveillance requires periodic telephone calls, while passive surveillance does not Signup and view all the answers

Why is it important to have clear objectives for each surveillance item?

To ensure that the surveillance system is focused and productive Signup and view all the answers

Why is it important to evaluate the full surveillance system continually?

To ensure that the system is effective in detecting disease outbreaks Signup and view all the answers

What is an example of a change in medical care practice that uncovered a previously invisible disease surveillance issue?

A hospital began reporting many cases of pharyngeal gonorrhea in young children Signup and view all the answers

Why are surveillance systems for non-infectious diseases and conditions often difficult to establish?

Lack of significant support and funding from governments Signup and view all the answers

What is a limitation of using death certificates to monitor fatal diseases?

Diagnoses are often inaccurate Signup and view all the answers

What is the main goal of syndromic surveillance?

To characterize 'syndromes' consistent with agents of particular concern Signup and view all the answers

What is shown in Figure 3-9?

The impact of the two types of polio vaccines on reported incident cases of poliomyelitis Signup and view all the answers

Why did the rates of paralytic disease decline quickly after the introduction of the inactivated vaccine in 1955?

Because of the rapid adoption of the inactivated vaccine Signup and view all the answers

What can indicate the failure of a vaccine?

A lack of change in disease rates or an increase in disease rates after an initial decrease Signup and view all the answers

What was the result of postmarketing surveillance of measles vaccines and vaccination schedules?

The detection of the failure of the initial measles vaccines to provide long-lasting protection Signup and view all the answers

What can be inferred from studying the patterns of occurrence of a particular disease over time?

The changing patterns of the disease Signup and view all the answers

Why was there a greater effort to detect tuberculosis in people with AIDS?

Due to the increasing impact of the AIDS epidemic Signup and view all the answers

Why is data on disease patterns important for setting disease control priorities?

Because it helps establish priorities for disease control efforts Signup and view all the answers

What does the oral polio vaccine provide in addition to individual immunity?

Herd immunity Signup and view all the answers

What is the definition of an epidemic?

The unusual occurrence of a disease Signup and view all the answers

What would be considered an epidemic in a region where a disease has been eradicated?

A single case of the disease Signup and view all the answers

What term is used to describe a disease that is deeply entrenched in an animal population?

Enzootic Signup and view all the answers

What is the attack rate used to measure?

The proportion of exposed persons that becomes ill Signup and view all the answers

What is the purpose of the constant multiplier in the attack rate equation?

To express the rate as a percentage Signup and view all the answers

What is the term used to describe a disease that occurs regularly and at a more or less constant level in a population?

Endemic Signup and view all the answers

Why would a single case of a disease be considered an epidemic in a region where it has been eliminated?

Because it has the potential for spread Signup and view all the answers

What is the difference between an epidemic and an endemic disease?

An epidemic is an unusual occurrence, while an endemic disease is a regular occurrence Signup and view all the answers

What determines the data needed to classify persons as affected or unaffected?

Case definition Signup and view all the answers

What type of graph is used to describe the time dimension of an outbreak?

Epidemic time curve Signup and view all the answers

What type of exposure would result in an epidemic time curve with a sudden onset, peak, and rapid decline?

Common source exposure Signup and view all the answers

What is the term for the case that introduced the organism into the population?

Index case Signup and view all the answers

What type of outbreak would result in an epidemic time curve with a prolonged, irregular pattern?

Person-to-person spread Signup and view all the answers

What can cause an epidemic time curve to have multiple peaks?

All of the above Signup and view all the answers

What is the term for the period of time between exposure to a disease and the onset of symptoms?

Incubation period Signup and view all the answers

What is the purpose of creating an epidemic time curve?

To understand the outbreak and answer important questions Signup and view all the answers

What type of transmission can result in an epidemic time curve similar to a common source exposure?

Respiratory transmission Signup and view all the answers

What is the primary goal of investigating an epidemic?

To discover and correct recent changes to restore balance Signup and view all the answers

What is the first step in investigating a disease outbreak?

Establish the diagnosis Signup and view all the answers

What is the purpose of the epidemiologic case definition?

To decide whether or not a person has the disease of concern Signup and view all the answers

Why is it important to establish a case definition early in an outbreak investigation?

To establish consistent criteria for epidemiologic investigations Signup and view all the answers

What is necessary to determine if an epidemic is occurring?

Cases occurring in sufficient numbers to constitute an epidemic Signup and view all the answers

What is characterized by time, place, and person in an outbreak investigation?

The epidemic Signup and view all the answers

What is the significance of knowing the usual number of cases in ongoing surveillance?

It helps to determine if an epidemic is occurring Signup and view all the answers

Why is it important to investigate an outbreak?

To discover and correct recent changes to restore balance Signup and view all the answers

What can be a result of a correct diagnosis during an outbreak investigation?

The outbreak is stopped Signup and view all the answers

What is a limitation of establishing a case definition?

There are always some false positives and false negatives Signup and view all the answers

What is the primary purpose of using the epidemic time curve in an outbreak investigation?

To determine the probable time of exposure Signup and view all the answers

What is the typical range of incubation period for Shigella organisms?

12 to 96 hours Signup and view all the answers

What can be inferred from the geographic clustering of cases in an outbreak investigation?

Important clues about the source of the outbreak Signup and view all the answers

Why do epidemiologists prefer to show incidence rates by location instead of using spot maps?

Because spot maps do not provide information on the denominator Signup and view all the answers

What is the limitation of using spot maps in outbreak investigations?

They only show the numerator and not the denominator Signup and view all the answers

What was the probable cause of the outbreak of respiratory fungal infection in the Arkansas school?

Coal dust contaminated with Histoplasma capsulatum Signup and view all the answers

What can be inferred from comparing trends in incidence rates in different regions?

The spread of a disease from one region to another Signup and view all the answers

What can help epidemiologists decide whether a cluster of disease cases represents an environmental problem?

The types of cancer in the cluster Signup and view all the answers

What is the next step after identifying a cluster of disease cases?

Begin observing the situation prospectively Signup and view all the answers

What characteristic of affected individuals may help clarify the cause of an outbreak?

All of the above Signup and view all the answers

What may indicate a true environmental problem in an area?

A cluster of disease cases with a single type or a small number of related types of cancer Signup and view all the answers

What is a difficulty in distinguishing 'chance' clusters from 'real' clusters of disease?

The theory of random sampling Signup and view all the answers

What can be a problem in neighborhoods or small areas?

Clusters of disease cases Signup and view all the answers

What is the primary difference between a common-source outbreak and a propagated outbreak?

Common-source outbreaks have a single point of exposure, while propagated outbreaks spread from person to person Signup and view all the answers

What is the purpose of conducting laboratory studies in epidemiology?

To test epidemiologic hypotheses Signup and view all the answers

What is an example of a common-source exposure?

Eating contaminated spaghetti Signup and view all the answers

What is the mode of transmission of an epidemic disease that involves contact with contaminated objects?

Through fomites Signup and view all the answers

What is the purpose of a case-control study in epidemiology?

To identify risk factors Signup and view all the answers

What is the significance of the second dose of measles vaccine in preventing outbreaks?

It prevents outbreaks of measles Signup and view all the answers

What is the purpose of a serum test in laboratory studies?

To detect antibodies to the suspected organism Signup and view all the answers

What is an example of a propagated pattern of spread?

Shaking hands with someone who is sick Signup and view all the answers

What is the term used to describe a disease that occurs regularly and at a more or less constant level in a population?

Endemic Signup and view all the answers

What is the purpose of testing hypotheses in epidemiology?

To understand the pattern of spread Signup and view all the answers

What is the primary purpose of initiating control measures during an outbreak?

To prevent further transmission of the disease Signup and view all the answers

What is an example of a sanitation effort to control an outbreak?

Removing the pathogenic agent from the source of infection Signup and view all the answers

Why is it important to communicate findings to the appropriate authorities, health professionals, and the public during an outbreak?

To enable other agencies to assist in disease control and contribute to the professional fund of knowledge Signup and view all the answers

What is the purpose of initiating specific follow-up surveillance after an outbreak?

To evaluate the effect of the control measures Signup and view all the answers

What is an example of a prophylaxis measure to control an outbreak?

Putting a barrier to the infection, such as a vaccine Signup and view all the answers

What is the purpose of modification of the environment in sanitation efforts?

To prevent contact with the source of infection Signup and view all the answers

What was the probable source of the outbreak of acute gastrointestinal illness at the college?

A food handler who worked while ill Signup and view all the answers

What was the symptom that most students experienced during the outbreak?

Nausea and vomiting Signup and view all the answers

What is the primary objective of diagnosis and treatment during an outbreak?

To prevent further transmission of the disease Signup and view all the answers

Why is it important to have active surveillance after an outbreak?

It is more reliable than passive surveillance Signup and view all the answers

What was the purpose of developing a case definition for the investigation?

To define a case for the purpose of the investigation Signup and view all the answers

What is the primary function of public health agencies in investigating disease outbreaks?

Detecting and reporting acute outbreaks Signup and view all the answers

What is the significance of laboratory data in investigating disease outbreaks?

To test hypotheses regarding the source of infection Signup and view all the answers

What is the purpose of follow-up surveillance after an outbreak?

To evaluate control measures Signup and view all the answers

What is the main goal of surveillance in public health?

To set disease control policy Signup and view all the answers

What is the role of the practicing physician in disease surveillance?

To detect acute outbreaks Signup and view all the answers

Study Notes

Surveillance of Disease

Surveillance is the entire process of collecting, analyzing, interpreting, and reporting data on the incidence of death, diseases, and injuries and the prevalence of certain conditions.
The Centers for Disease Control and Prevention (CDC) is the federal agency responsible for the surveillance of most types of acute diseases in the United States.

Creating a Surveillance System

A surveillance system requires clear objectives regarding the diseases or conditions to be covered.
The objectives for each surveillance item should be clear, and the criteria for defining a case of a reportable disease or condition must be known.
The intensity of the planned surveillance (active vs. passive) and duration of the surveillance (ongoing vs. time-limited) must be known in advance.

Methods and Functions of Disease Surveillance

Surveillance may be either passive or active.
Passive surveillance is when physicians, clinics, laboratories, and hospitals report disease cases, while active surveillance involves periodic telephone calls, electronic contact, or personal visits to obtain data.
The percentage of patients with reportable diseases that are actually reported to public health authorities varies considerably.

Establishment of Baseline Data

Usual (baseline) rates and patterns of diseases can be known only if there is a regular reporting and surveillance system.
Epidemiologists study the patterns of diseases by the time and geographic location of cases and the characteristics of the persons involved.

Evaluation of Time Trends

Secular (long-term) trends in disease are usually different from those of outbreaks or epidemics and often carry greater significance.
Seasonal variation is a common pattern in infectious diseases, with periods of highest incidence usually depending on the route of spread.

Identification and Documentation of Outbreaks

An epidemic, or disease outbreak, is the occurrence of disease at an unusual (or unexpected) frequency.
To determine that the level of a disease is unusual, the usual rates of the disease must be known, and reliable surveillance must show that current rates are considerably elevated.

Surveillance for Bioterrorism

Epidemiologists have worried about the use of biologic agents for military or terrorist purposes.
Special surveillance techniques are being developed to enable rapid detection of major increases in the most likely biologic agents.

Evaluation of Public Health and Disease Interventions

The introduction of major interventions intended to change patterns of disease in a population should be followed by surveillance to determine if the intended changes were achieved.
Surveillance can help detect the failure of a vaccine to produce satisfactory immunity or the failure of people to use the vaccine.

Setting of Disease Control Priorities

Data on the patterns of diseases for the current time and recent past can help governmental and voluntary agencies establish priorities for disease control efforts.

Study of Changing Patterns of Disease

By studying the patterns of occurrence of a particular disease over time in populations and subpopulations, epidemiologists can better understand the changing patterns of the disease.

Investigation of Epidemics

Definition of an epidemic: an unusual occurrence of a disease, derived from Greek roots meaning "upon the population"
Can be a single case of a disease that has been eliminated or eradicated from a region

Terms for Disease Patterns in Animals

Epizootic: a disease outbreak in an animal population
Enzootic: a disease deeply entrenched in an animal population but not changing much

Attack Rate

Measures disease frequency
Calculated as: (Number of new cases / Number of persons exposed) x 100
Expressed as a percentage

Procedures for Investigating an Epidemic

Establish the diagnosis
Establish an epidemiologic case definition
Determine if an epidemic is occurring
Characterize the epidemic by time, place, and person

Characterizing an Epidemic

Time: use an epidemic time curve to show the number of new cases over time
Place: create a spot map to show the location of cases
Person: gather information on age, gender, race, ethnicity, religion, and other personal characteristics of affected individuals

Developing Hypotheses

Identify the source of infection
Determine the pattern of spread (common-source, propagated, or mixed)
Identify the mode of transmission### Modes of Transmission
Respiratory transmission
Fecal-oral transmission
Vector-borne transmission
Skin-to-skin transmission
Transmission through exchange of serum or other body fluids
Transmission through contact with fomites (objects that can passively carry organisms)

Laboratory Studies

Cultures from patients and possible vehicles (e.g., food, water)
Stool examinations for ova and parasites
Serum tests for antibodies to suspected organisms
Tests for nonmicrobiologic agents (e.g., toxins, drugs)

Case-Control Studies

Assemble cases (people with the disease) and controls (people without the disease)
Question both groups about specific foods eaten before the outbreak
Calculate the percentage of controls who consumed each food item and subtract from the percentage of cases who consumed it
Identify the food item with the greatest difference in consumption percentage between cases and controls as the most likely risk factor

Control Measures

Sanitation: modify the environment to remove the pathogenic agent
Prophylaxis: use a barrier to infection (e.g., vaccine, immunization)
Diagnosis and treatment: treat infected individuals to prevent spread
Control of disease vectors (e.g., mosquitoes, ticks)

Follow-up Surveillance

Evaluate the effect of control measures
Detect subsequent outbreaks
Active surveillance is more reliable than passive surveillance

Investigation of an Outbreak

Define the case criteria
Conduct interviews with affected people
Analyze the epidemic time curve
Identify possible risk factors (e.g., food handlers working while ill)
Consider past knowledge from similar outbreaks and disease surveillance
Make recommendations based on the investigation's findings

Surveillance of Disease Activity

Surveillance is the foundation of public health control of disease and can be active or passive.
The functions of surveillance include determining baseline rates of disease, detecting outbreaks, and evaluating control measures.

Investigation of Disease Outbreaks

Investigation of disease outbreaks is a primary function of public health agencies.
Practicing physicians contribute to detecting and reporting acute outbreaks.
The standard approach to investigating disease outbreaks involves:
- Making a diagnosis
- Establishing a case definition
- Determining whether there is a definite outbreak

Characterizing Outbreaks

If an outbreak is occurring, cases are characterized by:
- Time (using an epidemic time curve)
- Place (determining rates in people who live and work in different locations)
- Person (determining personal characteristics and patterns of people involved in the outbreak)

Developing and Testing Hypotheses

Hypotheses are developed regarding:
- Source of infection
- Pattern of spread
- Mode of transmission
Hypotheses are tested using:
- Laboratory data (e.g., cultures, paired sera, analysis for toxins)
- Research methods (e.g., case-control studies)

Control Measures and Follow-up

Control measures and follow-up surveillance are initiated as soon as practical.
This is done to prevent further transmission of the disease.

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Learn about the process of disease surveillance, its importance, and how it promotes public health. Discover the role of Centers for Disease Control and Prevention (CDC) in the United States.

Preventive Medicine: Epidemiology 3

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Questions and Answers

What is the primary purpose of disease surveillance?

What is the foundation of disease control efforts?

What is required for the development of a surveillance system?

What do epidemiologists study to understand patterns of diseases?

What may be responsible for the observed changes in disease patterns?

What does a long-term increase in a disease in one region suggest?

Why do infectious diseases that are spread by the respiratory route have a higher incidence in the winter and early spring?

What is the effect of the introduction of varicella vaccine on the seasonal pattern of varicella?

What is the purpose of incorporating seasonal variation into calculations?

What is the significance of a long-term trend in disease?

When are most diseases spread by insect or arthropod vectors typically acquired?

What is the purpose of using an 'epidemiologic year'?

Why does recreational drowning occur more frequently on weekends?

What is an epidemic?

How does the CDC determine when and where influenza and pneumonia outbreaks occur?

What is the main concern of surveillance for bioterrorism?

What makes detection of bioterrorism more difficult?

What is the purpose of special surveillance techniques in bioterrorism?

What is the primary objective of surveillance in determining the effectiveness of a vaccine program?

What is typically used to define a case of a reportable disease or condition?

What is the main difference between active and passive surveillance?

Why is it important to have clear objectives for each surveillance item?

Why is it important to evaluate the full surveillance system continually?

What is an example of a change in medical care practice that uncovered a previously invisible disease surveillance issue?

Why are surveillance systems for non-infectious diseases and conditions often difficult to establish?

What is a limitation of using death certificates to monitor fatal diseases?

What is the main goal of syndromic surveillance?

What is shown in Figure 3-9?

Why did the rates of paralytic disease decline quickly after the introduction of the inactivated vaccine in 1955?

What can indicate the failure of a vaccine?

What was the result of postmarketing surveillance of measles vaccines and vaccination schedules?

What can be inferred from studying the patterns of occurrence of a particular disease over time?

Why was there a greater effort to detect tuberculosis in people with AIDS?

Why is data on disease patterns important for setting disease control priorities?

What does the oral polio vaccine provide in addition to individual immunity?

What is the definition of an epidemic?

What would be considered an epidemic in a region where a disease has been eradicated?

What term is used to describe a disease that is deeply entrenched in an animal population?

What is the attack rate used to measure?

What is the purpose of the constant multiplier in the attack rate equation?

What is the term used to describe a disease that occurs regularly and at a more or less constant level in a population?

Why would a single case of a disease be considered an epidemic in a region where it has been eliminated?

What is the difference between an epidemic and an endemic disease?

What determines the data needed to classify persons as affected or unaffected?

What type of graph is used to describe the time dimension of an outbreak?

What type of exposure would result in an epidemic time curve with a sudden onset, peak, and rapid decline?

What is the term for the case that introduced the organism into the population?

What type of outbreak would result in an epidemic time curve with a prolonged, irregular pattern?

What can cause an epidemic time curve to have multiple peaks?

What is the term for the period of time between exposure to a disease and the onset of symptoms?

What is the purpose of creating an epidemic time curve?

What type of transmission can result in an epidemic time curve similar to a common source exposure?

What is the primary goal of investigating an epidemic?

What is the first step in investigating a disease outbreak?

What is the purpose of the epidemiologic case definition?

Why is it important to establish a case definition early in an outbreak investigation?

What is necessary to determine if an epidemic is occurring?

What is characterized by time, place, and person in an outbreak investigation?

What is the significance of knowing the usual number of cases in ongoing surveillance?

Why is it important to investigate an outbreak?

What can be a result of a correct diagnosis during an outbreak investigation?

What is a limitation of establishing a case definition?

What is the primary purpose of using the epidemic time curve in an outbreak investigation?

What is the typical range of incubation period for Shigella organisms?

What can be inferred from the geographic clustering of cases in an outbreak investigation?

Why do epidemiologists prefer to show incidence rates by location instead of using spot maps?

What is the limitation of using spot maps in outbreak investigations?

What was the probable cause of the outbreak of respiratory fungal infection in the Arkansas school?

What can be inferred from comparing trends in incidence rates in different regions?

What can help epidemiologists decide whether a cluster of disease cases represents an environmental problem?

What is the next step after identifying a cluster of disease cases?

What characteristic of affected individuals may help clarify the cause of an outbreak?

What may indicate a true environmental problem in an area?

What is a difficulty in distinguishing 'chance' clusters from 'real' clusters of disease?

What can be a problem in neighborhoods or small areas?

What is the primary difference between a common-source outbreak and a propagated outbreak?