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Case study

Question 1: Would you call this an epidemic? Would you call it an outbreak?

Yes this is an epidemic because you have defined in your power point that epidemic is health-related state or event in a defined population above the expected over a given period of time. Yes it is an outbreak.

Question 2

Review the steps of an outbreak investigation.

We have seven steps:

(1)  Detecting a possible outbreak

(2)  Defining and finding cases

(3)  Generating hypotheses about likely sources

(4)  Testing the hypotheses

(5)  Finding the point of contamination and source of the food

(6)  Controlling an outbreak

(7)  Deciding an outbreak is over

Question 3

List the broad categories of diseases that must be considered in the differential diagnosis of an outbreak of gastrointestinal illness.

Answer: Staphylococcus aureus, Bacillus cereus, Clostridium perfringens, Salmonella (nontyhpoid), Pufferfish poisoning (tetrodotoxin), shigella, giardia lamblia, Escherichia coli enterohemorrhagic (E. coli O157:H7 and, campylobacteria, Paralytic shellfish poisoning, Ciguatoxin, Poisonous mushroom, Clostridium botulinum, Cryptosporidium parvum, Cyclospora cayetanensis, Yersinia enterocolitica, Vibrio cholerae O1 or 0139, Rotavirus, Listeria monocytogenes- Invasive Disease, C. Heavy metals Antimony Cadmium, Copper, Iron, Tin and Zinc.

Question 4

In epidemiologic parlance, what is a vehicle? What is a vector? What are other modes of transmission?

Answer

What is a vehicle? Vehicle-borne (non-living intermediary) (e.g., HIV/AIDS spread through infected blood on used hypodermic needle)

What is a vector? A vector is an invertebrate animal (Malaria spread through mosquitoes)

What are other modes of transmission? Direct, person-to-person contact (e.g., STDs)

Fomite-borne (inanimate object) (e.g., Hepatitis A spread by a contaminated eating utensil)

Fomite is a type of vehicle.

Question 5

If you were to administer a questionnaire to the church supper participants, what information would you collect? Group the information into categories.

Answer

Demographic: Location: where did you eat the food? How many adults were they? How many children were they? Age group, sex.

Clinical: What time the food was consumed? At which point the discomforts start? Is there any food left for the test? Has this happen to them before or these are new symptoms? Have them try to take something to relive it if so what was it and what time? Did you eat something before the church’s food if so what was it? Did you share the food with someone else beside the church and family member if so can you give me their names?

Laboratory: is there any food left for the test?

Inform the CDC for further investigation.

Question 6

What is a line listing?

A line listing allows information about time, person, and place to be organized and reviewed quickly. It is also a good way to keep track of different categories of cases. For example, cases can be entered into the line listing as possible, probable or confirmed (laboratory confirmed, clinically confirmed or both).

What is the value of a line listing? They are laboratory values collected and put in line listing.

Question 7

What is the value of an epidemic curve?

Answer: An epidemic curve is a graphic depiction of the number of outbreak cases by date of illness onset. It is useful because it can provide information on the outbreak’s such as: Pattern of spread, Magnitude, Outliers, Time trend, Exposure and/or disease incubation, period.

Question 8

Using the graph paper provided, graph the cases by time of onset of illness (include

appropriate labels and title). What does this graph tell you?

Most people were sick from 10:30 am the next day from what they ate on the 18 of April. From 11pm on the 18 of April, only few people experience illness. The graph has shown that most people were ill on the next day.

Question 9

Are there any cases for which the times of onset are inconsistent with the general experience?

Yes there were cases where the times of onset are inconsistent including 9pm, 9:15pm, 9:30 pm, 10pm, 10:30 pm, 11pm and 11:30pm on the 18th of April.

How might they be explained? People digest food in different ways. Some have a delay in digestion while others digest faster that is why one can notice different onset illness time.

Question 10

How could the data in the line listing be better presented?

The data could be better presented by putting time from the earlier onset to the last onset illness.

Question 11

Where possible, using the new line listing, calculate incubation periods and illustrate their distribution with an appropriate graph.

8p to 12:30am=4h: 30min, 6:30 to 12:30=6hours, 7p :30 to 10:30p=3h30min, 7:30p to 2:00am= 7:30hours, 10p to 1:00am=3hrs, 7p to 11p=4hours, 10pm to 1am=3hours,

Question 12

Determine the range and median of the incubation period.

The range= largest number - smallest number=7:30-3=4h30

Median=3hours

Question 13

How does the information on incubation period, combined with the data on clinical symptoms, help in the differential diagnosis of the illness? (If necessary, refer to attached Compendium of Acute Foodborne Gastrointestinal Disease).

The information on incubation period combined with the data on clinical symptoms, help in the differential diagnosis of the illness to determinate what type of disease is out breaking. Different diseases with different incubation time.

Question 14

Using the data in the attached line listing, complete the table below. Which food is the

most likely vehicle of infection?

Food Items Served / Number of persons who ATE
specified food / Number of persons did NOT eat
specified food / Attack Rate Ratio
Ill / Not Ill / Total / Percent Ill
(Attack rate) / Ill / Not Ill / Total / Percent Ill
(Attack rate)
Baked ham / 46 / 29 / 75 / 61.3% / 29 / 29 / 29 / 38.7%
Spinach / 43 / 32 / 75 / 32
Mashed potato / 37 / 37 / 75
Cabbage salad / 28 / 47 / 75
Jello / 23 / 52 / 75
Rolls / 37 / 38 / 75
Brown bread / 27 / 48 / 75
Milk / 4 / 71 / 75
Coffee / 31 / 44 / 75
Water / 24 / 51 / 75
Cakes / 40 / 35 / 75
Ice cream, vanilla / 54 / 21 / 75
Ice cream, chocolate / 47 / 27 / 75
Fruit salad / 6 / 69 / 75

I had misunderstanding on the table I was not sure what I was doing was right.

Question 15

Outline further investigations that should be pursued.

·  How many people will be affected, and will think of an outbreak to look for help.

·  They can also investigate what was the condition of those who cooked the meal and ice cream.

Question 16

What control measures would you suggest?

Wash and cook food well before eat. They can use contact measure if there is stool involve or droplet precaution if respiration, high temperature or sneezing are involved.

Question 17

Why was it important to work up this outbreak?

It was important to work up this outbreak to prevent further break.

Question 18

Refer to the steps of an outbreak investigation you listed in Question 2. How does this investigation fit that outline?

It fits in term of researchers be able to have some elements in their hands to work with including testing hypothesis of people who ate ice cream and who made it.