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Read the following
summary.
An outbreak of E.
coli O157:H7 gastroenteritis occurred in central Nebraska in February
and March of 1999. E. coli O157:H7 is a bacteria that produces a toxin
that can cause diarrhea (often bloody), abdominal cramps, and can affect
the kidneys. E. coli O157:H7 can be transmitted person-to-person via the
fecal-oral route. E. coli O157:H7 can also be transmitted by
contaminated food or water. Nationwide, there has been evidence that ill
food handlers may have been the source of an outbreak. Children aged less
than 16 years and adults aged greater than 65 years are at greater risk
of developing complications, including kidney failure. A total of 72
persons became ill. Nearly all of the affected person experienced
diarrhea and abdominal cramps. Eight persons required hospitalization,
including one child who required dialysis due to kidney failure. Of the
72 ill persons, 65 were exposed while dining at the family reunion on
February 26 and seven were exposed secondarily.
Questions
- Construct 2 case
definitions differentiating how the ill persons were exposed. (5
points each)
Primary
case-patient:
Secondary
case-patient:
Telephone
interviews were conducted over a period of two weeks to obtain food and
illness history. Analysis of the food history and illness data yielded
two food items associated with illness. The following are the 2 x 2
tables for the food items.
Ranch Dressing
| |
Got
ill?
|
| Yes |
No |
Total |
| Ate
the dressing? |
|
|
|
| Yes |
18 |
17 |
35 |
| No |
46 |
54 |
100
|
| Total |
64 |
71 |
135 |
Iceburg Lettuce
| |
Got
ill?
|
| Yes |
No |
Total |
| Ate
the lettuce?
| |
|
|
| Yes |
57 |
29 |
86 |
| No |
8 |
40 |
48 |
| Total |
65 |
69 |
134 |
- Calculate the
attack rate for each food item. (5 points each)
- Which food item
explains the greater percentage of illness? (3 points)
- During the course
of the environmental investigation, it was learned that the ranch
dressing was used in preparation of the seafood salad. Describe how
you would account for this in your analysis. (10 points)
- As well as
interviewing the attendees, another important group to interview is
the food handlers. These interviews will help shed light on the
origin of the outbreak. Please list five items of information that
you should obtain from the food handlers. (10 points)
- John Snow detected
the source of an outbreak of (2 points)
A. Typhoid fever
B. Cholera
C. Malaria
D. Plague
- John Snow stopped
the above outbreak by removing the handle of a neighborhood water
pump. (2 points)
True/False
- A cohort study is
used in an outbreak setting when a complete list of participants is
available. (2 points)
True/False
- The measure of
risk used in a cohort study is the odds ratio. (2 points)
True/False
- A case-control
study is used in an outbreak setting when a complete list of
participants is available. (2 points)
True/False
- The measure of
risk used in a case-control study is the odds ratio. (2 points)
True/False
The following
co-workers became ill following an in-office Chinese New Year
celebration held on February 3 at 12:00 PM:
Chris (February
4, 4:00 a.m.)
Karen (February 4, 7:30 a.m.)
Bob (February 4, 10:00 a.m.)
Tom (February 4, 10:00 a.m.)
Josh (February 4, 8:00 p.m.)
Jane (February 4, 11:30 p.m.)
Adi (February 4, 12:00 p.m.)
Wayne (February 4, 11:00 a.m.)
Kim (February 4, 9:00 a.m.)
John (February 4, 4:12 p.m.).
- Please construct
an epidemic curve using 2-hour increments on the graph paper
provided. Please include a legend for the figure. (5 points)
- Describe the
historical (1950 to 1996) trend of measles in the United States,
using the attached graph.
Include your interpretation of the impact of measles vaccine. (10
points)
- In the late
1980s and early 1990s, outbreaks of measles occurred on numerous
college and high school campuses. Give your impression(s) as to
what factors allowed this to occur. (5 points)
- As a result of
this increase of measles, what public health recommendation(s)
was/were made? (5 points)
- Describe the
trend of salmonellosis in the United States from 1966 to 1996 and
include three possible reasons for the change. (10 points)
- Salmonella is
detected and grown during routine stool culture for enteric
pathogens. Salmonella is further typed by identifying antigens on
its cell body (O antigen) and flagella (H antigen) to determine
setotypes. Serotypes are very useful epidemiologically. For
example, S. enteriditis is the serotype most frequently associated
with eggs. An increase in an uncommon serotyope raises suspicion
of an outbreak. Using the graph on salmonella serotypes, describe
the trend of salmonellosis in the United States from 1971 to 1996.
How does this change your previous interpretation of salmonellosis
in the United States? (10 points)
Answer
Key
Tiebreaker #1
Please match the
following outbreak settings with the agent causing the outbreak.
Some diseases may be used more than once or not at all.
| Outbreak
Settings |
Agent
Causing Outbreak |
- __ Kitwit, Zaire, 1995
- __
Jack-in-the-Box, Pacific NW, 1993
- __ New
Mexico/Arizona Four Corners, 1993
- __
Meatpacking plant employees, Omaha, 1999
- __
Public school students eating frozen strawberries, United
States, 1997
- __
Restaurant-associated, Kearney, 1999
- __
Mosquito-associated, New York City, 1999
- __
"Party in the Pasture" or Cornstalk, Illinois,
1999
- __
Laboratory Monkeys, Reston, VA, 1989
- __
Salad-bar associated bioterrorism event, Oregon, 1987
|
- Shigella
- Hepatitis
A
- Salmonella
- Ebola/Ebola
related viruses
- E. coli
O157:H7
- Rubella
- Hantavirus
- Measles
- West
Nile Virus
- Botulism
|
Tie breaker #2
Please calculate the relative risk for iceberg lettuce using the
2x2 table in Question #2.
Answer Key
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