Matt Kuntz
MPH 510
Week 3
Case Study
Part 1
1. I would call this an outbreak. The CDC says that an outbreak is when a large number of
people become sick with the same illness at the same time and same place. All of these people in
the cluster of sick people must have something in common to explain why they are all sick in
order for the illness to be an outbreak. Because all of the sick people in this case study ate dinner
at the same church, they all have something in common making this an outbreak, not an
epidemic.
2. In order to investigate outbreaks, epidemiologists go through a process of steps in order to
prevent, control, and treat illnesses. The first step in this process is detecting a possible outbreak.
Formal reporting plays a big part in this step. If enough cases form a cluster and the cluster has
something in common as to why they are getting sick, then epidemiologist move to the second
step of defining and finding cases. To help keep track of illness and find more cases they use an
epidemic curve graph to put illnesses in patterns and keep records. Generating hypotheses about
likely sources is the next step in this process. By asking questions, interviewing, and
administering surveys, epidemiologists are able to track certain things that sick people have in
common. Once a hypothesis is made, the 4th step of testing the hypothesis is next. A hypothesis
should be tested to determine if the source has been correctly identified. Investigators use many
methods to test their hypotheses in order to fulfill the 5th step of finding the point of
contamination. This is done by tracing back to the common issue that all sick people have in
common. Once the source is found, it is time to control the outbreak. Controlling the outbreak is
step number 6. In this step, many things can be done. Cleaning is the biggest concern in
controlling outbreaks. Other measures taken may be in the form of educating the public or
closing a specific place down for a few days. Once the number of illness reach its normal
number, the 7th and final step of deciding the outbreak is over may be done.
3. Broad categories that must be considered in the diagnosis of an outbreak:
Diseases typified by vomiting after short incubation with no fever
Diseases typified by diarrhea after a moderate to long incubation, with fever
Disease readily diagnosed from history of eating a particular type of food
4. What is a vehicle, what is a vector, what are other modes of transmission?
A vehicle is a mode of transmission of a disease. Examples are contaminated water, infected
blood, and food.
A vector is an animate, living insect or animal involved with transmission of a disease agent.
Examples are ticks, flies, and mosquitoes.
Other modes of transmission are droplet, direct contact, and airborne transmissions
5. Questionnaire for dinner participants:
I would administer questions to not only the people who ate there but also the people in charge of
dinner. There are three categories I would concentrate on.
Food:
I would collect information on what foods were at the dinner
I would ask what each person ate
I would see if there was any cross contamination between spoons, forks, cooking utensils,
or serving platters
I would ask who prepared each food item
Drinks:
I would see what drinks people had
If ice was used in any drinks
If there were cans, bottles, or cups
Illness:
I would track the symptoms each person was feeling
I would see if family members were sick
When symptoms started
How long symptoms lasted
6. What is line listing and what is the value of line listing?
Line listing is data that is recorded and put into columns so epidemiologists can analyze and
interpret information efficiently. This form of data collection if very valued because it can help
graph epidemic curves and help determine the case of a disease.
Part 2
7. The use of the epidemic curve is to show illnesses over time. It is very valuable because
epidemiologist can determine the cause of disease by tracking when people got sick in relation to
when and what they ate. The pattern of the epidemic curve can help investigators decide if ill
persons were exposed to the same source of illness over a short period or if the exposure to the
source was over a longer time.
8. Graph on graph paper
9. Are there any cases for which the times of onset are inconsistent with the general experience?
Explain.
One case that stood out to me was number 16. This person said the time of onset was at 10:30 am
on 4/19. Some reasons for this could be the person took food home and ate it for a snack, the
person may have slept through the illness, or the person may not have ingested enough of the
vehicle that carried the bacteria.
Another case that stood out to me was number 52. This person must have been around the
bacteria prior to it being served to everyone else
10. How could the data in the line listing be better presented?
Putting the data in order of the time of onset could better present the data in the line listing. To
me, it is very hard to compare cases having them spread out like they are. I would also like to be
able to look at the time of the meal and compare it with the time of the onset of illness. The way
the chart is set up does not allow this to be done very easily.
The line listing also has the foods that were at the meal. To better present the data on this chart,
percentages of sick people consuming each food could be figured out. With this information, you
get a better picture of what the cause of the illness could be.
Part 3
11. Incubation period is the time interval between exposure to an infectious agent and the
appearance of the first symptoms.
Graph on separate graph paper
12. Determine the range and median of the incubation period.
Range- 7-3 = 4
Median- 4.3 hours
13. The information on incubation period combined with the data on clinical symptoms will help
decipher what the cause of illness could be by weeding out everything that does not meet the
constraints of our incubation period for this case. Since our low number is 3 hours, the cause of
this illness should have a lower number than 3. Since our high number is 7, the high number of
the cause should not be too much higher than 7. If a disease has a low period that is above 7, we
know that it cannot be the cause. Once we weed these causes out, we can narrow it down to a
few causes.
14. On separate sheet
15. Outline further investigations that should be pursued.
* Who made each food?
* Was or is anyone currently sick prior to the outbreak
* If the area where the dinner was held was cleaned properly before dinner
* If serving dishes or utensils were shared
* What foods needed refrigerated
* How long each food sat out before being served
* How long each food sat out throughout the night
16. What control measures would you suggest?
I would suggest:
Cleaning the entire area where the dinner was held.
Cleaning serving dishes and utensils appropriately.
Getting rid of all the food that was at the dinner in case there was cross contamination.
Continue to monitor to see if others are getting sick
17. Why is it important to work up this outbreak?
It’s important to work out an outbreak like this to make sure the illness is not something that can
potentially turn into an epidemic. Knowing that it was a food borne illness and nothing that was
contagious from person to person brings relief because you can stop the source and control it
before too many people are affected.
18. How does this investigation fit the outline in number 2?
This investigation fits my outline in number two in most ways. Dr. Rubin detected there was a
problem, figured out who was sick and who was not, made a hypotheses about how the illness
was brought about, found the point of contamination, and controlled the outbreak.
Friis, R., & Sellers, T. (2014). Epidemiology for public health practice. (5th ed.). Burlington,
MA : Jones and Barrlett
Foodborne outbreak investigations. (2012, Aug 09). Retrieved from
http://www.cdc.gov/outbreaknet/investigations/investigating.html