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Part 1. Multiple Choice
1.
Epidemiology would include which of the following activities?
A. Describing the demographic characteristics of persons with acute aflatoxin poisoning in District A
B. Prescribing an antibiotic to treat a patient with community-acquired methicillin-resistant
Staphylococcus aureus infection
C. Comparing the family history, amount of exercise, and eating habits of those with and without newly
diagnosed diabetes
D. Recommending that a restaurant be closed after implicating it as the source of a hepatitis A outbreak
2.
Which of the following is NOT a goal of epidemiology?
a. To discover the agent, host, and environmental factors that affect health
b. To determine the relative importance of causes of illness, disability, and death
c. To identify those segments of the population that have the greatest risk from specific causes of ill
health
d. To evaluate the effectiveness of health programs and services in improving population health
e. To provide clinical treatment for individuals and populations that experience disease outbreaks
3.
On Day 1 of a technology conference in Camden, NJ 12 presenters who were setting up for their sessions
at the Convention Center became ill with flu-like symptoms. During the course of the conference, 16
participants who attended the conference also became ill with the same symptoms.
To begin calculating the rate of this outbreak, investigators should first determine
a. The number of case illnesses
b. The number of persons who attended the conference
c. The number of days the conference was held
d. a and b
e. a and c
4.
Observational studies are conducted in an attempt to
a. monitor the public health in preparation for a potential outbreak
b. determine whether or not an outbreak has occurred
c. discover associations between an exposure or risk factor and a health outcome
d. test the investigator’s hypothesis regarding agent, host, illness
e. evaluate the efficacy of specific public health interventions
5.
The hallmark feature of an analytic epidemiologic study is: (Choose one best answer)
A. Use of an appropriate comparison group
B. Laboratory confirmation of the diagnosis
C. Publication in a peer-reviewed journal
D. Statistical analysis using logistic regression
6.
Subjects are selected in a cross-sectional study because
a. they are members of a certain population at a certain time
b. they have been identified by their exposure to one or more risk factors
c. they have been positively identified as having a disease condition
d. they have been positively identified as NOT having a disease condition
e. c or d
7.
A study of individuals who ate at a particular Taco Bell in Atlanta between October 15th and 20 th is an
example of
a. a cross-sectional study
b. a case-control study
c. a cohort study
d. a experimental study
e. a case report
8.
To establish the existence of an outbreak, investigators are NOT likely to use data from
a. surveys and questionnaires
b. testing samples taken from the environment
c. notifications to the health department if cases are observed
d. social media: Face-Book, Twitter, Snap-Chat, etc.
e. financial records, legal records, sales records
9.
A true increase in the incidence of a disease may be attributed to
a. improvements in diagnostic procedures
b. outbreak of a similar disease, misdiagnosed as disease of interest
c. laboratory error
d. an antigenic shift that results in a more virulent strain of agent
e. changes in local reporting procedures
10. A cohort study differs from a case-control study in that:
A. Subjects are enrolled or categorized on the basis of their exposure status in a cohort study but not in a
case-control study
B. Subjects are asked about their exposure status in a cohort study but not in a case control study
C. Cohort studies require many years to conduct, but case-control studies do not
D. Cohort studies are conducted to investigate chronic diseases, case-control studies are used for
infectious diseases
11. The epidemiologic triad of disease causation refers to: (Choose one best answer)
A. Agent, host, environment
B. Time, place, person
C. Source, mode of transmission, susceptible host
D. John Snow, Robert Koch, Kenneth Rothman
12. In the following table, the total number of persons with the disease is:
A.
B.
C.
D.
E.
3
22
25
34
50
13. The best estimate of the association between wedding cake and illness is:
A. 6.1
B. 7.7
C. 68.4
D. 83.7
E. 91.7
F. 94.3
14. To study the causes of an outbreak of aflatoxin poisoning in Africa, investigators conducted a case-control
study with 40 case-patients and 80 controls. Among the 40 poisoning victims, 32 reported storing their
maize inside rather than outside. Among the 80 controls, 20 stored their maize inside. The resulting odds
ratio for the association between inside storage of maize and illness is:
A. 3.2
B. 5.2
C. 12.0
D. 33.3
15. 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. Clinical criteria, plus specification of time, place, and person
B. Clinical features, plus the exposure(s) you most suspect
C. Suspect cases
D. The nationally agreed standard case definition for disease reporting
Part 2. Fill-in the blank
16. A report form sent to regional health facilities to gather surveillance data should include the following:
information about the reporter, information about patients, demographic information, and ______.
17. A sudden rise in the occurrence of a disease is known as a(n) _____.
18. If a disease spreads over a larger area infecting many communities it may be termed a(n) _____.
19. The _____ rate is the number of new cases of a disease divided by the number of individuals at risk.
20. The most common vehicle for botulinum toxin produced by Clostridium botulinium is _______.
21. Houseflies may transfer Shigella from their appendages to a food item. In this mode of transmission the
flies are acting as a _____.
Base your answer to the next question on the following data
22. Calculate the relative risk______ associated with eating ice cream and getting ill.
23. Determine the median time and date of onset in the following chart.
24. The U.S. Centers for Disease Control and Prevention (CDC) estimates that 48 million people in the U.S.
suffer from foodborne illness each year resulting in 138,000 hospitalizations and 3,000 deaths.
Based on these estimates, calculate the prevalence of foodborne illness (per 100,000) in the U.S. in 2015
(July 1st 2015 population 321,418,820).
25. In an epidemic of hepatitis A traced to green onions from a restaurant, 555 cases were identified. Three of
the case patients died as a result of their infections. Calculate the case-fatality rate.
The next two questions are based on the same outbreak of foodborne illness.
26. Consider an outbreak of shigellosis in which 18 persons in 18 different households all became ill. If the
population of the community was 1,000. Calculate the overall attack rate.
27. One incubation period later, 17 persons in the same households as these “primary” cases developed
shigellosis. If the 18 households included 86 persons, calculate the secondary attack rate.
Consider the outbreak of hepatitis A illustrated by the chart below for the next two questions.
The incubation period for hepatitis A ranges from 15 to 50 days (roughly 2 to 7 weeks), with an average
incubation period of 28–30 days. Because cases can occur from 15 to 50 days after exposure, all cases from a
point source exposure should occur within a span of 50 – 15 = 35 days.
28. True or False? This outbreak is consistent with a single point source exposure.
29. What is the date of onset of the first case?
30. On what date (month/day) is the exposure most likely to have occurred?
31. The table above is called a ___.
32. Construct a two by two table of botulism illness with exposure to chili.
Label columns and rows and include data.
33. Construct an epidemic-curve of these data.
Part 3. Outbreak Investigations
A. Deaths Associated With Bacterial Pathogens Transmitted Commonly Through
Food: Foodborne Diseases Active Surveillance Network (FoodNet), 1996–2005
The Journal of Infectious Diseases 2011;204:263–7
Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2011.
Background. Foodborne diseases are typically mild and self-limiting but can cause severe illness and death. We
describe the epidemiology of deaths associated with bacterial pathogens using data from the Foodborne Diseases
Active Surveillance Network (Food-Net) in the United States.
Methods. We analyzed Food-Net data from 1996–2005 to determine the numbers and rates of deaths
occurring within 7-days of laboratory-confirmation.
b AAPMR are given as deaths/1 million people
Respond to the following questions based on the data in Table 1.
34.
35.
36.
37.
38.
What was the most common cause of death from food borne illness in the U.S. from 1996-2005?
What percentage of cases are attributed to Campylobacter?
What is the ratio of deaths by Salmonella to deaths by Campylobacter?
How many people would be expected to die of Listeria infection per 100,000 cases?
Approximately how many people died each year from Listeria infection from 1996-2005?
( July 1, 2000 N= 282.16 million)
Respond to the following questions based on the data in Table 2.
39. What age-specific cohort is most suseptible to death due to food borne illness according to Table 2?
40. Support your answer with data from Table 2.
41. Explain why this cohort is more suseptible to death than the other age-specific groups.
B. Multistate Shigellosis Outbreak and Commercially Prepared Food, United
States
Shigella infects an estimated 450,000 people annually in the United States and is usually transmitted through
person-to-person spread (1,2). During January 18–21, 2000, California, Oregon, and Washington reported 406
cases of drug-resistant gastroenteritis that developed in several persons after they ate a commercially prepared
(brand X), five-layered bean dip; stool cultures yielded S. sonnei. A cohort study of an outbreak at a party implicated
this dip; five of six ill attendees had eaten brand X dip compared with none of six well attendees (relative risk = 7.0;
95% confidence interval 1.1 to 42.9). On January 21, the manufacturer began a voluntary recall of the bean dip. We
conducted a nationwide investigation to determine the magnitude and severity of the outbreak, confirm its source,
and identify the mechanism of contamination.
42. An epidemiological investigation to determine the source and mechanism of an outbreak can also be
called a(n) (descriptive, analytical) study. Choose one.
43. To detect an outbreak and monitor dangerous diseases, epidemiologists often depend on reports from
health agencies. This is known as (passive, active) surveillance. Choose one.
44. Shigella sonnei is a (disease, pathogen, vector). Choose one.
45. Relative risk is a (ratio, proportion, rate). Choose one.
46. Stool cultures that test positive are necessary to identify cases that are laboratory (likely, probable,
confirmed). Choose one.
47. Because people are already sick before this study is started, this would be an example of a (retrospective,
prospective) cohort study.
48. Relative risk measures the probability that ________ will lead to illness.
49. Inflammation of the stomach and intestines is referred to as ____________.
50. What was the first control measure or intervention in this case?
Imagine you are the investigator on this case of toxic bean dip. Consider the steps of your outbreak
investigation. Fill-in the four missing steps to complete your investigation.
prepare for field work
establish the existence of an outbreak
51.
52.
53.
54.
_____
_____
_____
_____
implement control measures
establish surveillance measures
communicate findings
This dip was epidemiologically implicated as the outbreak source through a cohort study and supported by these
findings: 1) patients in several states whose only reported common exposure was the dip and who had
genetically-matched S. sonnei infections; 2) isolation of S. sonnei from brand X dip; and 3) outbreak termination
after the product was recalled.
Numerous problems in manufacturing practices were noted at the dip-production facility, which suggests that
the contamination occurred there, probably by an infected employee.
The evolving epidemiology of foodborne outbreaks reflects changes in the way that food is processed and
distributed. The consumer can be educated to cook or wash minimally processed products such as raw meats, eggs,
and fresh produce thoroughly before eating. However, in the case of a ready-to-eat product such as this dip, the
responsibility to ensure safety of the product before opening rests with the growers, manufacturers, distributors,
and retailers.
55. State one intervention that could be implemented to ensure greater safety of our ready-to-eat food.
In this outbreak, a drug-resistant, virulent organism was rapidly disseminated through a commercially processed
product. Although this outbreak was likely unintentional, it illustrates the vulnerability of the food supply, which is
increasingly characterized by centralized production and broad distribution, and the potential for commercially
produced food to be used in an act of bioterrorism. Intentional contamination of a ready-to-eat, widely distributed
food product with an organism that has a low infectious dose (e.g., Shigella) can cause considerable illness and can
be extremely costly in terms of personal, medical, and public health resources.
56. State on intervention that could be implemented to minimize the risk or impact of bioterrorism through
our food supply.
C. Carrier Prevalence, Secondary Household Transmission, and Long-Term
Shedding in 2 Districts During the Escherichia coli O104:H4 Outbreak in
Germany, 2011 The Journal of Infectious Diseases 2013;207:432–8
Background. From May through July 2011, Germany experienced a large outbreak of Shiga toxin–producing
Escherichia coli (STEC) O104:H4 infection causing 2987 cases of gastroenteritis, 855 cases of hemolytic-uremic
syndrome (HUS), and 53 deaths. The outbreak’s epidemic profile, which differed substantially from that of previous
outbreaks of E. coli infection, and notification data can be explained to a great extent by the causing vehicle: cases
were predominantly adults, with a median age of 46 years, for gastroenteritis, and 42 years, for HUS. Furthermore,
cases mostly occurred among women (58% of gastroenteritis cases and 68% of HUS cases). The estimated median
incubation period was 8 days (interquartile range, 6– 10 days).
Answer the following questions based on the data in Table 1
Table 1. Consumption of Food Items Among Cases and Non-Cases
and Association With Disease Outcome During the Shiga-toxin
Producing Escherichia coli O104:H4 Outbreak in Germany, 2011
57. Calculate the odds ratio (OR) for the raw tomatoes.
[You will need to use the (%) to find the total number of
cases and non-cases.]
58. According to the data, which food item appears to be the
source of infection?
59. Why did cases of infection occur mostly in women (median
age 46)?
Non–
Cases
No. (%) OR (95% CI) P
Food item
Cases
No. (%)
Sprouts
31 (60.8) 10 (6.3)
<.001
Cucumber
39 (72.2) 64 (39.5)
<.001
Raw tomatoes 46 (78.0) 80 (49.1)
<.001
Lettuce
41 (71.9) 73 (46.2)
.001
Ground meat
(beef)
18 (38.3) 75 (47.5)
.269
Unpasteurized 11 (20.4) 32 (20)
milk
products
1 (.5–2)
.953
Objective: The aims of this investigation are to identify the prevalence of STEC O104:H4 carriers in households in
highly affected areas, the rate of secondary household transmissions, and the duration of long-term shedding (i.e.
emission of pathogens from a host’s body which may facilitate spread to new hosts).
A case was defined as (1) a notified STEC gastroenteritis or HUS case (hemolytic-uremic syndrome) with serogroup
O104 or unknown serogroup and onset of disease after 30 April 2011, residing in the district of Herzogtum
Lauenburg or Schleswig-Flensburg, or (2) a symptomatic or asymptomatic STEC O104:H4 infection that was
diagnosed during our investigation by detection of STEC O104:H4 in a stool sample. Disease onset was defined as
onset of bloody or non-bloody diarrhea, with diarrhea defined as ≥2 loose stools within 24 hours. A person with
detection of STEC O104:H4 after symptomatic or asymptomatic infection was considered a carrier.
60. List the 4 parts of a case definition.
This study was conducted in 2 parts. First, we screened for STEC O104:H4 carriers in households with ≥2 members
that did or did not have reported cases of STEC-associated gastroenteritis or HUS. Screening of households was
performed 3–10 weeks after first notification of the outbreak.
61. Is this part of the study descriptive or analytical in nature?
62. Is this part of the study observational or experimental?
63. Is this an ecological or cross-sectional study design?
Second, we followed households in which a carrier was identified to determine rates of secondary household
transmission and duration of shedding among STEC O104:H4 carriers. Households with ≥1 carrier and ≥1
household member without reported STEC gastroenteritis or HUS prior to and at the time of screening were
enrolled in the study. At 14-day intervals, all participants were asked to provide stool samples and information on
gastrointestinal symptoms since the last stool sample. At the first follow-up sampling, the questionnaire also
contained questions on household and participants' characteristics and hand hygiene practice. Stool sampling
continued until all household carriers tested negative for STEC O104:H4. A negative test had to be confirmed by 2
additional STEC O104:H4–negative samples on 2 consecutive days.
64. Which term best describes the study design of part 2 of this investigation?
A. retrospective cohort study
B. prospective cohort study
C. randomized control trial
D. case-control study
Match each of the following statements from this investigation (65-69) with the type of error or bias (A-D) that
each exemplifies.
A. selection bias
B. information bias
C. measurement error
D. confounding factors
65. The small sample size of our study and, therefore, its limited power makes conclusive statements on STEC
O104:H4 carrier prevalence and household transmissions difficult.
66. Mainly because of logistic reasons, the targeted interval between consecutive sampling events was not
met.
67. Furthermore, contacts in the study population was aware of carrier(s) in the household, and it may have
caused behavior (e.g. an increase in hand-washing) that decreased the chance of secondary infection.
68. Response in our study differed between districts, which could be due to differences in recruitment
methods. In Schleswig-Flensburg, disease severity of cases may have resulted in a lower response, as this
district had the highest reported HUS incidence; compared with an overall HUS incidence of 25% among
cases during the outbreak [3], HUS was reported for only 6% of cases in our study population.
69. Stool sampling procedures and transport conditions until arrival at the laboratory may have resulted in
lower sensitivity.
Results. For part 1, we recruited 57 case households (62 case patients and 93 household contacts) and 36 control
households (89 household members). We only detected cases in previously known case households and identified 1
possible adult-to-adult household transmission. For part 2, we followed 14 households and 20 carriers. No
secondary household transmission was detected in the follow-up period. In 1 adult carrier, shedding lasted >7
months. However, the median estimated shedding time was 10–14 days (95% confidence interval, 0–33 days).
Three carriers showed intermittent shedding.
Conclusions. The prevalence of STEC O104:H4 carriers even in highly affected areas appears to be low. Despite
prolonged shedding in some patients, secondary adult-to-adult household transmissions seem to be rare events in
the post-diarrheal disease phase.
70. With consideration to the findings in this investigation, when do you think a person who has been
infected with STEC 0104:H4 should be able to return to work... if they work in the food industry…handling
food?