Deck 19: Epidemiology

Question 1

A news station reported about a potentially fatal epidemic disease occurring in a small African village. An epidemiologist from the CDC was interviewed to discuss the disease and was very distressed that it was not being contained. Why did the epidemiologist feel the disease was a concern for people in North America?

Answer 1

World travel makes it likely that the disease can spread beyond the borders of Laos. Depending on how the disease spreads, the organism or vectors that transmit the disease-causing agent can make its way around the world.

Question 2

A student disagreed with the presentation of the examples in figure 19.9. She claimed that the number of cases from a common-source outbreak could remain high over a much longer period of time in some cases and not decrease to zero. Is the student's claim reasonable? Why or why not?

FIGURE 19.9 Comparison of Propagated Versus Common-Source Epidemics (a) The time between the index case and subsequent cases reflects the average incubation period of the disease. As the disease is propagated, this interval is blurred. (b) Cases in a common-source epidemic appear only within the incubation period.

Answer 2

A common-source outbreak could continue to produce a large number of new cases if the source continued to infect individuals. For example, if a single restaurant continued to serve contaminated food over a long period of time, new cases would arise and the peak of the curve could remain high until the source of contamination was eliminated. The student is correct in her claim, but most common-source outbreaks are short-lived as shown in the diagram.

Question 3

Communicable diseases can be transmitted from one host to another. Rates of disease within a population are a concern of epidemiologists who study disease patterns. An unusually large number of cases within a population constitutes an epidemic.
Name two typical sources of non-communicable diseases.

Answer 3

Infectious diseases the can be transmitted from one person (either directly or indirectly) to the other are called , "communicable or contagious diseases." Examples include, conjunctivitis and ebola.
Diseases that are not transmitted directly from one host to the other are called, "non-communicable diseases."
The microbes causing non-communicable diseases generally arise from the normal microbiota of an individual or from the environment. The two general sources of transmission of non-communicable diseases are,
• The microbiota of the host
• Environmental sources such as contaminated water systems, wind, and others
Examples of non-communicable diseases include, Legionnaires disease or legionellosis caused by " Legionella pneumophila." Legionellosis is not transmitted from person to person, but it is transmitted through the contaminated warm natural waters, or from the water systems in the buildings.

Question 4

Which of the following is an example of a fomite?

A) Table
B) Flea
C) Staphylococcus aureus carrier
D) Water
E) Air

Question 5

Compare the impact on a society of an endemic debilitating disease with high incidence to the impact on society of a similar disease with high prevalence.

Question 6

An international team was gathered to discuss how funding should be spent to eliminate human infectious disease. There is only enough funding to eliminate one disease. How would the scientists go about choosing the next disease to be eliminated from the planet?

Question 7

As shown in the graphs below, the proportion of deaths due to cancer and heart disease in the United States today is much higher than it was in 1900. Explain the factors that most likely contribute to this difference.

Question 8

Communicable diseases can be transmitted from one host to another. Rates of disease within a population are a concern of epidemiologists who study disease patterns. An unusually large number of cases within a population constitutes an epidemic.
Explain the difference between incidence of a disease and prevalence of the disease.

Question 9

Which of the following would be the easiest to eradicate?

A) A pathogen that is common in wild animals but sometimes infects humans
B) A disease that occurs exclusively in humans, always resulting in obvious symptoms
C) A mild disease of humans that often results in no obvious symptoms
D) A pathogen found in marine sediments
E) A pathogen that readily infects both wild animals and humans

Question 10

What is the epidemiologic significance of people who have asymptomatic infections?

Question 11

Communicable diseases can be transmitted from one host to another. Rates of disease within a population are a concern of epidemiologists who study disease patterns. An unusually large number of cases within a population constitutes an epidemic.
Why might a disease be endemic in one region, but not in another?

Question 12

Which of the following methods of disease transmission is the most difficult to control?

A) Airborne
B) Foodborne
C) Waterborne
D) Vector-borne
E) Direct person to person

Question 13

Explain why zoonotic diseases are often severe in humans.

Question 14

Spread of a disease can be prevented by breaking the chain of infection. The reservoir of a disease agent can be infected people, other animals, or the environment. To spread, infectious microbes must exit one reservoir, be transmitted to a susceptible host, and then enter that host. Handwashing and vector control can prevent many diseases; airborne transmission of pathogens is difficult to control.
How can an insect act as both a mechanical vector and a biological vector?

Question 15

Which of the following statements is false?

A) A botulism epidemic that results from improperly canned green beans is an example of a common-source outbreak.
B) Droplet nuclei fall quickly to the ground.
C) Congenital syphilis is an example of a disease acquired through vertical transmission.
D) Plague is endemic in the rock squirrel population in parts of the United States.
E) The first case in an outbreak is called the index case.

Question 16

List the main portals of exit from the human body.

Question 17

Spread of a disease can be prevented by breaking the chain of infection. The reservoir of a disease agent can be infected people, other animals, or the environment. To spread, infectious microbes must exit one reservoir, be transmitted to a susceptible host, and then enter that host. Handwashing and vector control can prevent many diseases; airborne transmission of pathogens is difficult to control.
How does handwashing reduce the spread of disease?

Question 18

Which of the following statements is false?

A) A disease with a long incubation period might spread extensively before an epidemic is recognized.
B) A person exposed to a low dose of a pathogen might not develop disease.
C) The young and the aged are more likely to develop certain diseases.
D) Malnourished populations are more likely to develop certain diseases.
E) Herd immunity occurs when a population does not engage in a given behavior, such as eating raw fish, that would otherwise increase their risk of disease.

Question 19

Name the most important control measure for preventing person-to-person transmission of a disease.

Question 20

Spread of a disease can be prevented by breaking the chain of infection. The reservoir of a disease agent can be infected people, other animals, or the environment. To spread, infectious microbes must exit one reservoir, be transmitted to a susceptible host, and then enter that host. Handwashing and vector control can prevent many diseases; airborne transmission of pathogens is difficult to control.
Considering that circulating blood is not normally released from the body, describe how blood-borne microbes might exit.

Question 21

The purpose of an analytical study is to

A) identify the person, place, and time of an outbreak.
B) identify risk factors that result in high frequencies of disease.
C) assess the effectiveness of preventive measures.
D) determine the effectiveness of a placebo.
E) None of the above

Question 22

Describe the factors within a population that may make it more susceptible to infectious disease.

Question 23

The outcome of disease transmission is affected by the virulence, dose, and incubation period of the infecting agent; various characteristics of the host population; and environmental conditions surrounding the pathogen and the host.
Explain how a low dose of an infectious agent can result in an asymptomatic infection.

Question 24

If you and your family all develop infectious diarrhea, the most likely portal of entry for the pathogen was the

A) large intestine.
B) mouth.
C) skin.
D) respiratory tract.
E) nose.

Question 25

Draw representative epi curves (time versus number of people ill) depicting a propagated and a common-source epidemic.

Question 26

The outcome of disease transmission is affected by the virulence, dose, and incubation period of the infecting agent; various characteristics of the host population; and environmental conditions surrounding the pathogen and the host.
Why are diseases with long incubation periods more likely to result in an epidemic?

Question 27

All of the following are thought to contribute to the emergence of disease except

A) advances in technology.
B) breakdown of public health infrastructure.
C) construction of dams.
D) mass distribution and importation of food.
E) widespread vaccination programs.

Question 28

Differentiate among a case-control study, a cross-sectional study, and a cohort study.

Question 29

The outcome of disease transmission is affected by the virulence, dose, and incubation period of the infecting agent; various characteristics of the host population; and environmental conditions surrounding the pathogen and the host.
Why do influenza outbreaks in nursing homes typically have higher case-fatality rates than influenza outbreaks in a college dormitory?

Question 30

Which of the following common causes of healthcareassociated infections is an environmental organism that grows readily in nutrient-poor solutions?

A) Enterococcus
B) Escherichia coli
C) Pseudomonas aeruginosa
D) Staphylococcus aureus

Question 31

What information is available in the Weekly Epidemiological Record?

Question 32

Descriptive epidemiologic studies attempt to identify the potential risk factors that lead to disease. Analytical studies try to determine which suspected factors are actually relevant to disease development. Experimental studies are generally used to evaluate the effectiveness of a treatment or an intervention in preventing disease.
On what three factors can a descriptive study focus?

Question 33

What is the most common type of nosocomial infection?

A) Bloodstream infection
B) Gastrointestinal infection
C) Pneumonia
D) Surgical wound infection
E) Urinary tract infection

Question 34

How does the assignment of individuals to groups in a cohort study differ from assignment of individuals to groups in an experimental study?

Question 35

Descriptive epidemiologic studies attempt to identify the potential risk factors that lead to disease. Analytical studies try to determine which suspected factors are actually relevant to disease development. Experimental studies are generally used to evaluate the effectiveness of a treatment or an intervention in preventing disease.
How is the timing of a propagated epidemic related to the incubation period of the pathogen?

Question 36

Describe the factors that contribute to the emergence or reemergence of disease.

Question 37

Descriptive epidemiologic studies attempt to identify the potential risk factors that lead to disease. Analytical studies try to determine which suspected factors are actually relevant to disease development. Experimental studies are generally used to evaluate the effectiveness of a treatment or an intervention in preventing disease.
Why is it important to include a placebo in a scientific study to assess the effectiveness of a drug?

Question 38

What are the main reservoirs of nosocomial infections?

Question 39

Across the United States, a network of agencies, including the Centers for Disease Control and Prevention (CDC) and state and local public health departments, monitors disease development. The World Health Organization (WHO) is devoted to achieving the highest possible level of health for people around the globe. Humans have been successful in reducing or eliminating certain diseases.
What is the MMWR ?

Question 40

Across the United States, a network of agencies, including the Centers for Disease Control and Prevention (CDC) and state and local public health departments, monitors disease development. The World Health Organization (WHO) is devoted to achieving the highest possible level of health for people around the globe. Humans have been successful in reducing or eliminating certain diseases.
Explain why smallpox was successfully eradicated, but rabies probably never will be.

Question 41

Across the United States, a network of agencies, including the Centers for Disease Control and Prevention (CDC) and state and local public health departments, monitors disease development. The World Health Organization (WHO) is devoted to achieving the highest possible level of health for people around the globe. Humans have been successful in reducing or eliminating certain diseases.
Explain why we have relatively accurate data on the number of cases of measles that occur in the United States but not on the number of cases of the common cold.

Question 42

Microbes are adept at responding to change. Evolution of the pathogen, changes in human behavior, or climate change can provide new opportunities for pathogens to thrive.
Why might a person immunized against cholera contract the disease anyway?

Question 43

Microbes are adept at responding to change. Evolution of the pathogen, changes in human behavior, or climate change can provide new opportunities for pathogens to thrive.
How would you expect a trend toward warmer climates to affect the spread of vector-borne disease?

Question 44

Microbes are adept at responding to change. Evolution of the pathogen, changes in human behavior, or climate change can provide new opportunities for pathogens to thrive.
What political and societal factors might lead to a decrease in childhood immunizations?

Question 45

Healthcare-associated infections may originate from other patients, the healthcare environment, healthcare workers, or the patient's own normal microbiota. Diagnostic and therapeutic procedures can potentially transmit infectious agents. The most important steps in preventing healthcare-associated infections are to first detect their occurrence and then establish policies to prevent their development.
Explain why an IV catheter poses a risk to a patient.

Question 46

Healthcare-associated infections may originate from other patients, the healthcare environment, healthcare workers, or the patient's own normal microbiota. Diagnostic and therapeutic procedures can potentially transmit infectious agents. The most important steps in preventing healthcare-associated infections are to first detect their occurrence and then establish policies to prevent their development.
Describe two ways in which infectious agents can be transmitted to a patient.

Question 47

Healthcare-associated infections may originate from other patients, the healthcare environment, healthcare workers, or the patient's own normal microbiota. Diagnostic and therapeutic procedures can potentially transmit infectious agents. The most important steps in preventing healthcare-associated infections are to first detect their occurrence and then establish policies to prevent their development.
Explain why the rate of nosocomial infections is often relatively high in emergency room settings.