2021 University of Texas at Austin Science Olympiad Invitational
Disease Detectives B/C
KEY
Rules
● DO NOT WRITE ON THIS EXAM!! Only the answer sheet will be graded.
● Each team is permitted one letter-sized page of notes and two non-programmable,
non-graphing calculators.
● Write your team number on the top right corner of each page (4 pts).
● Tiebreaker questions are marked with an asterisk.
● Point values are given for each question.
● Teams may take apart the exam and staple it together when turning it in.
● Show all work and units for partial credit.
● Round to three decimal places unless told otherwise.
● AGAIN, DON’T WRITE ON THE EXAM.
SECTION 1: BACKGROUND AND SURVEILLANCE
Match the words to their definitions.1 (16 pts)
A. outbreak
B. epidemic
C. cluster
D. pandemic
E. hypoendemic
F. hyperendemic
G. holoendemic
H. reservoir
I. vector
J.
K. pathogenicity
L. virulence
M. etiology
N. epidemiology
O. zoonosis
P. surveillance
fomite
1. The constant presence at high incidence and prevalence of an agent or health condition
within a given geographic area or population. F
2. An epidemic occurring over a widespread area (multiple countries or continents) and usually
affecting a substantial proportion of the population. D
3. An infectious disease that is transmissible from animals to humans. O
4. The habitat in which an infectious agent normally lives, grows, and multiplies, which can
include humans, animals, or the environment. H
5. The occurrence of more cases of disease, injury, or other health condition than expected in a
given area or among a specific group of persons during a specific period. A
6. An inanimate object that can be the vehicle for transmission of an infectious agent. J
7. An aggregation of cases of a disease, injury, or other health condition in a circumscribed area
during a particular period without regard to whether the number of cases is more than
expected. C
8. A living intermediary that carries an agent from a reservoir to a susceptible host. I
9. The occurrence of more cases of disease, injury, or other health condition than expected in a
given area or among a specific group of persons during a particular period. B
10. Characterized by the infection of essentially every individual in a defined population. G
11. A disease that is constantly present at a low incidence or prevalence and affects a small
proportion of individuals in the area. E
12. The ability of an agent to cause disease after infection, measured as the proportion of
persons infected by an agent who then experience clinical disease. K
1
Most definitions taken from the CDC’s Principles of Epidemiology textbook
13. The study of the distribution and determinants of health conditions or events among
populations and the application of that study to control health problems. N
14. The ongoing systematic collection, analysis, and interpretation of health data that are
essential to the planning, implementation, and evaluation of public health practice. P
15. The ability of an infectious agent to cause severe disease, measured as the proportion of
persons with the disease who become severely ill or die. L
16. The cause or causes of a disease or abnormal condition. M
17. State the type of surveillance (active, passive, sentinel, syndromic) used in each scenario
below. (4 pts)
a. Every month, Montana hospitals send disease reports to the Montana Department
of Public Health. passive
b. Harris County Public Health asks every hospital within the county to send all data
about food poisoning in the month of July. active
c. A worker at a hospital notices a sudden spike in cases involving symptoms of
encephalitis and notifies public health authorities. syndromic
d. A small group of hospital workers is responsible for reporting every case of
influenza to public health authorities. sentinel
18. State one advantage and one disadvantage of syndromic surveillance. (2 pts)
Advantages: can give more detailed data
Disadvantages: takes longer, uses more resources
19. Fill in the diagram with the natural history of disease. (4 pts)
a.
b.
c.
d.
e.
f.
Exposure
Pathological changes
Onset of symptoms
Usual time of diagnosis
Stage of susceptibility
Stage of subclinical disease
g. Stage of clinical disease
h. Stage of recovery, disability, or death
20. Explain the primary difference between the public and the clinical approaches to health. (2
pts)
The clinical approach focuses on the health of an individual while the public health approach
focuses on the health of a community.
21. Place the three following causes of death in order from least annual deaths to most annual
deaths in the U.S.: breast cancer, pancreatic cancer, alcohol overdose (*Tiebreaker, 2 pts)
Alcohol overdose, breast cancer, pancreatic cancer
22. Who discovered the existence of prions and was awarded the 1997 Nobel Prize in Medicine?
(1 pt)
a. Richard Koch
b. Stanley Pruisner
c. John Snow
d. Jonas Salk
23. Which of the following is not a significant achievement of Louis Pasteur to microbiology? (1
pt)
a. Dispelling spontaneous germination
b. Creating the rabies vaccine
c. Being the father of germ theory
d. Being the first to identify microbes under the microscope
24. Which of the following scientists is considered the father of modern surgery? (1 pt)
a. Joseph Lister
b. Francesco Reddi
c. Lazarro Spallanzani
d. Van Leeuwenhoek
25. Whose work demonstrated that hand-washing could drastically reduce the number of
women dying after childbirth? (1 pt)
a. Thomas R. Frieden
b. Ignaz Semmelweis
c. Jonas Salk
d. Rudolph Virchow
26. Who was it that determined that plague was carried on fleas which were on the back of rats?
(1 pt)
a. Francis Home
b. Augostino Bassi
c. Ronald Ross
d. Paul Louis-Simond
27. Which antibacterial is reserved for MDR bacterial infections (in U.S.) and has a beta-lactam
structure (*Tiebreaker, 3 pts)
a. Vancomycin
b. Chloramphenicol
c. Macrolides
d. Carbapenems
SECTION 2: PATTERNS, CONTROL, AND PREVENTION
For each of the following situations (28-32), identify which term it reflects. (5 pts - 1 each)
a.
b.
c.
d.
e.
Sporadic disease
Endemic disease
Hyperendemic disease
Pandemic disease
Epidemic disease
28. ___E___ 22 cases of legionellosis occurred within 3 weeks among residents of a particular
neighborhood (usually 0 or 1 per year)
29. ___C___ Average annual incidence was 364 cases of pulmonary tuberculosis per 100,000
population in one area, compared with national average of 134 cases per 100,000 population
30. ___D___ Over 20 million people worldwide died from influenza in 1918–1919
31. ___A___ Single case of histoplasmosis was diagnosed in a community
32. ___B___ About 60 cases of gonorrhea are usually reported in this region per week, slightly
less than the national average
For each of the following situations (33-35), identify the type of epidemic spread with which it is
most consistent. (3 pts - 1 each)
a. Point source
b. Intermittent or continuous common source
c. Propagated
33. ___C___ 21 cases of shigellosis among children and workers at a daycare center over a
period of 6 weeks, no external source identified incubation period for shigellosis is usually
1—3 days)
34. ___B___ 36 cases of giardiasis over 6 weeks traced to occasional use of a supplementary
reservoir (incubation period for giardiasis is 3-25 days or more, usually 7-10 days)
35. ___A___ 43 cases of norovirus infection over 2 days traced to the ice machine on a cruise
ship (incubation period for norovirus is usually 24–48 hours)
36. What type of study is known as a “snapshot in time''? (1 pt)
a. Case report
b. Longitudinal
c. Ecological
d. Cross-sectional
37. What is it called when a large proportion of individuals within a given population is
consistently infected with a disease? (1 pt)
a. Macroendemic
b. Holoendemic
c. Pandemic
d. Omniendemic
600 UT first-year students participated in UT’s annual Day of Service. Some students became ill
after eating the provided bagged lunch. The suspected culprit was the grilled chicken sandwich. The
population that participated in Day of Service was surveyed to determine who became ill.
True (T) or False (F)
38.
39.
40.
41.
42.
43.
(2 pts) This is a cohort study T
(2 pts) The correct computation to use is the odds ratio. F
(1 pt) The study is prospective. T
(2 pts) A disadvantage of this study is that there is possible time-order confusion. F
(1 pt) This study design is the fastest. F
(1 pt) The study design used is not ideal for rare diseases. T
44. What type of bias occurs when cases detected by screening programs have better prognosis
than cases detected between screening programs? (3 pts)
Length Bias
45. Which of these is NOT an example of random error? (1 pt)
a. Inaccuracies in 24 hour food intake recall
b. Recruiting sicker individuals into a study
c. Changes in an individual’s blood pressure over the course of a day
d. The sampled group does not reflect the age and sex of the population
46. Which fomite is most poorly mismatched with its disease? (1 pt)
a. Kitchen counter - HIV
b. Stereoscope - MRSA
c. Hairbrush - Rickettsia prowazekii
d. Bedpan - C. difficile
e. None
47. State whether the following studies are experimental or observational studies. You may use
the abbreviations E and O, respectively. Then further characterize the study as
cross-sectional (CS), case-control (CC), experimental (E), or cohort (C). (8 pts - 2 each)
a. People who have and have not eaten deli meats are enrolled in the study and tracked
over a period of time to determine if they develop colon cancer as a means of
determining whether eating deli meats is a risk factor for colon cancer. O, C
b. Bio-statistical study to determine the prevalence of colon cancer in the United States
controlling for variables such as age, gender, ethnicity, geographical and social
factors. O, CS
c. Determining whether eating deli meat is a risk factor for colon cancer by enrolling
people with and without colon cancer and scoring the quantity and frequency of
eating deli meat for each person in the study. O, CC
d. Performing a study in which lab mice are fed increasing amounts of deli meat to see
if they develop gastric cancer at a higher rate than their control counterparts. E, E
48. Ecological fallacy refers to: (1 pt)
a. Assessing exposure in large groups rather than in many groups
b. Assessing outcome in large groups rather than in small groups
c. Ascribing the characteristics of a group to every individual in that group
d. Examining correlations of exposure and outcomes rather than time periods
49. In which of the following types of study designs does a subject serve as their own control? (1
pt)
a. Prospective cohort study
b. Retrospective cohort study
c. Case-control study
d. Case-crossover study
Match the level of prevention to the scenario. (4 pts - 1 each)
50.
51.
52.
53.
____d____ Primary Prevention
____b____ Secondary Prevention
____a____ Tertiary Prevention
____c____ Quaternary Prevention
a. A patient undergoes chemotherapy to treat leukemia.
b. Physicians recommend that adult females are tested for cervical cancer at least once
every three years.
c. A cancer patient stops treatment and moves from the hospital into a hospice home.
d. The health department and the Board of Education begin a new pilot program
designed to keep children healthy by mandating participation in weekly physical
activities.
54. For a particular epidemic, R0 > 1. What does this mean in terms of how many uninfected
people will be affected by infected people? (2 pts)
Each infected person will infect more than one uninfected person.
55. Which of these factors does NOT have a major impact on R0? (1 pt)
a. Duration of illness
b. Route of transmission
c. Period of communicability
d. Interventions
56. Measles have an extremely high R0. Knowing this, why is it dangerous that a smaller
proportion of Americans are getting measles vaccinations each year? (Hint: think about the
relationship between R0 and herd immunity). (*Tiebreaker, 2 pts)
Measles are extremely contagious. Because of the high R0, the required proportion of
vaccinated Americans to achieve herd immunity is much higher. However, less Americans
are being vaccinated, so herd immunity protection is decreasing.
57. List one characteristic of diseases that makes eradication possible. (2 pts)
Any of the following: no animal reservoir, short persistence in environment, absence of
long-term carrier state, disease produces long-term immunity, vaccination produces
long-term immunity, herd immunity protects the susceptible, easily identified disease,
effective post-exposure vaccination
58. What is the only disease that has been eradicated globally? (1 pt)
Smallpox
SECTION 3: OUTBREAK INVESTIGATION
Part 1
59. An outbreak of a certain sickness occurs following a company dinner. Due to the nature of
the outbreak, it is suspected that the agent behind the outbreak is a foodborne illness. Below
lies all the food present at the event and the number of sick and healthy individuals that ate
or did not eat the food.
a. Given the outbreak was a foodborne illness, what type of epi-curve would one
expect to see? (1 pt)
Point-source
b. What type of statistic should you use in order to identify the food that most likely
was the cause of this outbreak? (1 pt)
Odds Ratio
c. For the correct risk statistic, what is the risk statistic for ice cream? (1 pt)
1.120 – 1.127
d. What food through the correct risk statistic has the highest likelihood of being the
cause of the outbreak? (1 pt)
eggs
60. You develop a test for a certain disease and these are the results you obtain following clinical
trials:
a. What term can be said to be the true negativity rate? (1 pt)
Specificity
b. What is the false positive in your tests? (1 pt)
6
c. What is the sensitivity of your tests? Round to 2 decimals (1 pts)
0.81
d. If the disease had a high fatality rate, would you choose to maximize sensitivity or
specificity? (1 pt)
Sensitivity
e. What does a probable case have that a possible case does not? (Answer in less than 4
words) (1 pt)
Lab verification
f. If one travels from a location with a low prevalence of a disease to a place with a
higher prevalence of a disease, which of these would increase? (there may be multiple
answers) (1 pt)
i. Sensitivity
ii. Specificity
iii. Predictive Positive Rate
iv. Predictive Negative Rate
v. None
g. If one travels from a location with a low prevalence of a disease to a place with a
higher prevalence of a disease, which of these would stay the same? (there may be
multiple answers) (1 pt)
i. Sensitivity
ii. Specificity
iii. Predictive Positive Rate
iv. Predictive Negative Rate
v. None
In August 2008, the Austin Department of Health detected an increase of reports ofCampylobacter
jejuni infections than expected. After an initial investigation, a nationally distributed brand of cheese
was implicated in the outbreak. Disease detectives established national surveillance and surveyed
customers of the implicated manufacturer. Cultures for bacteria were obtained from cheese samples,
the cheese plant, and tanker trailers that had transported the milk (used to make the cheese) to the
plant.
61. Disease detectives conducted a small case-control study of 20 individuals (10 cases and 10
controls). Brand X cheese was eaten by 8 of 10 cases compared with 1 of 10 controls.
Calculate the odds ratio. (4 pts)
36.00 or 36
62. Disease detectives determined that the first element of an outbreak was met in the above
scenario. List the other two criteria that this incident must meet to be considered an
outbreak. (2 pts)
a. location (Massachusetts)
b. specific time period (August 2008)
Alternate Answer: specific group of persons
63. This graph below shows the progress of an outbreak over 14 months in a population of 30
people. Each horizontal line represents one person. The down arrow indicates the date of
onset of illness. The solid line represents the duration of illness. The up arrow and the circle
represent the date of recovery and date of death, respectively.
a. Calculate the incidence rate from August 1st, 2013, to October 1st, 2014 as the
denominator. Express the rate per 100 population and round up (Hint: use midpoint
population) (2 pts)
14 per 100
b. Calculate the point prevalence on March 1, 2014. Express your answer as a
percentage rounded to one decimal place. (2 pts)
20.7%
c. Calculate the period prevalence from August 1st, 2013, to October 1st, 2014.
Express your answer as a percentage rounded to one decimal place. (2 pts)
26.7%
Part 2
It is your first day as an intern at the State Department of Public Health. Your first rotation is in a department
studying zoonotic diseases.
64. Provide one example of zoonosis. (1 pt)
Any disease transmitted by an animal.
Your supervisor informs you that an outbreak of a strange disease has been reported. Epidemiologists have already
confirmed the outbreak and all reported cases. Victims are between the ages of 13-55, with the majority being under
40 years old. Symptoms include fatigue, fever, vomiting, body aches, and joint pain. Very few cases resulted in
encephalitis. All cases occurred in Bevo Bayou between June-August 2020.
65. Write a case definition for the mystery disease. (4 pts)
Must include age of victims, symptoms, dates of occurrence, and location
66. What is encephalitis? (*Tiebreaker, 2 pts)
Inflammation of the brain
67. Which step of the outbreak investigation comes next? Use the set of 13 steps. Provide the
step number and name. (2 pts)
Step 5: find cases systematically and record information
Take off half points if they give “Step 5: describe and orient the data in terms of time, place,
and person”
The disease has been identified as West Nile Virus (WNV), which is mainly transmitted through mosquito bites. It
can also be transmitted through blood transfusion/organ transplant or from mother to child during pregnancy, delivery,
or breastfeeding.
68. Can WNV be transmitted vertically? Explain your answer. (2 pts)
Yes; vertical transmission refers to transmission from mother to child
69. Are the mosquitoes that transmit WNV considered biological or mechanical vectors? (1 pt)
Biological
70. What are three questions you could ask the patients affected by WNV to determine the
cause of the outbreak? (3 pts)
Accept any logical question that could lead to a cause
Number
Onset Date
Fatigue
Fever
Vomiting
Body Aches
Joint Pain
Lab Test
Conclusion?
1
6/10
Yes
Yes
Yes
Yes
Yes
Positive
confirmed
2
6/10
Yes
Yes
No
No
Yes
n/a
probable
3
6/23
Yes
Yes
Yes
Yes
Yes
Negative
DNM
4
7/1
No
No
No
No
No
Negative
DNM
5
7/1
Yes
Yes
Yes
Yes
Yes
Inconclusive
probable
6
7/19
No
Yes
No
Yes
No
Positive
confirmed
7
7/19
No
No
No
Yes
Yes
n/a
probable
8
7/19
No
Yes
No
No
No
Positive
confirmed
9
8/7
No
No
No
No
No
Positive
confirmed
10
9/8
Yes
Yes
Yes
Yes
Yes
Inconclusive
DNM
71. For each case in the chart above, fill the conclusion column with either Probable,
Confirmed, or Does Not Match. You may use the abbreviations P, C, and DNM. Assume
that there are no Suspected cases and all testing is accurate. (5 pts)
72. Create an epidemic curve using the cases in the above chart. Assume all cases are true cases.
Include ALL epicurve elements. (6 pts)
Must have title, x-axis label, y-axis label, dates on x-axis, and number of new cases on y-axis.
Take off ½ point if bars are touching. Should look something like this.
Another case of WNV has been identified.
73. Should this case be placed in isolation or quarantine? Why? (2 pts)
Isolation; isolation refers to the separation of the infected, while quarantine refers to the
separation of those who have been exposed but have not tested positive for infection (yet).
A series of unfortunate study errors occur during the investigation of the WNV outbreak.
Match the situation with the bias that BEST fits. (4 pts - 1 each)
74.
75.
76.
77.
____b____ Information Bias
____a____ Volunteer Bias
____c____ Interviewer Bias
____d____ Late-Look Bias
a. Investigators publish an advertisement asking for people to participate in a study
about WNV. 84 people respond and a study is conducted with those 84 participants..
b. Dr. Apple and Dr. Bee each interview two groups of patients. Dr. Apple chooses to
privately interview each member of the first group. Dr. Bee only conducts a group
interview with the second group.
c. Dr. Norman is interviewing patients with WNV. He assumes that only the male
patients would work in occupations that require outdoor work. He only asks the
male patients about their occupational risk factors - not the female patients.
d. Investigators are only able to interview patients who have recovered from WNV and
accidentally exclude those who are seriously ill or deceased from their investigation.
78. What is PulseNet? Should this outbreak be reported to PulseNet? Why or why not? (2 pts)
It is a molecular subtyping network run by the CDC specifically for foodborne disease
outbreaks. The outbreak should not be reported because it is not a case of foodborne illness.
You identify possible exposures and create two groups of people that were exposed and that weren’t exposed. Then, you
further divide people based on whether they have WNV.
79. What type of study is this? Be as specific as possible. What are two advantages and two
disadvantages of this type of study? (5 pts)
Retrospective cohort study (take off ½ point for not including retrospective)
Advantages: most accurate observational study, good measure of exposure, easier than
randomized controlled trial, can study multiple outcomes at once, good for rare exposures,
best information abt causation/risk
Disadvantages: time-consuming, expensive, loss to follow-up bias, inefficient for diseases
with high latency period, not good for rare diseases
The source of the outbreak has been identified. There has been large growth in the mosquito population in Bevo Bayou
due to COVID-19 preventing insect control efforts.
Match the situation with the criterion from Hill’s Criteria for Causation that BEST fits. (3 pts - 1
each)
80. ____c____ Consistency
81. ____b____ Specificity
82. ____a____ Temporality
a. Every patient with WNV could recount being bit by a mosquito before feeling
symptoms or testing positive.
b. The only disease that each patient contracted from a mosquito bite was WNV.
c. Investigators were able to look at CDC data from previous years. They discovered
that WNV outbreaks in other regions followed similar patterns and had similar
causes.
83. List three strategies to prevent spread of WNV. (3 pts)
Accept any logical answer, including but not limited to mosquito-spraying, wearing bug
spray, removing standing water, wearing long-sleeved clothing, using mosquito netting, etc.