Investigating an Outbreak

Question 1

what is an outbreak?

Answer 1

outbreak/epidemic exists when there are more cases of a particular disease than expected in a given area or among a specific group of people over a particular period of time

Question 2

why do we investigate an outbreak? (6)

Answer 2

1. to control and prevent disease
2. to determine the severity and risk to others
3. for research opportunities and to gain additional knowledge
4. training opportunities
5. program considerations (training and prevention)
6. public, political, or legal concerns

Question 3

what are the 7 steps of investigating an outbreak?

Answer 3

1. prepare for field work
2. verify outbreak
3. plot epidemic curve
4. calculate attack rates
5. determine source of epidemic
6. recommend control measures
7. follow up

Question 4

what are the 5 things that happen in step 1 of investigating an outbreak (preparing for field work)?

Answer 4

1. research what is known about the disease or symptoms
2. learn about demographics and customs of local population
3. make admin and travel arrangements
4. build your team with clear delineation of responsibilities and assignments

Question 5

what are the 4 things that happen in step 2 of investigating an outbreak (verifying outbreak)?

Answer 5

1. establish a case definition that is non-ambiguous with clinical/diagnostic verification if possible with person/place/time descriptions
2. identify and count cases of illness
3. determine if disease is above endemic levels or if looking at a different disease with similar symptom
4. develop and administer a questionnaire to determine demographics, behaviors, and exposures

Question 6

how is an epidemic curve plotted?

Answer 6

number of cases on the y axis by their date or time of onset (x axis)

Question 7

what does the overall pattern of an epidemic curve tell you?

Answer 7

the increase, peak, and decrease can tell type of epidemic and incubation period

Question 8

what can outliers of an epidemic curve tell you?

Answer 8

if a case is unrelated, early or late exposures, index case, secondary cases

Question 9

describe the epidemic curve of a vector borne disease (3)

Answer 9

1. starts slowly (climate effects can modify)
2. the time between the 1st case and peak is comprable to incubation period
3. slow tail, will rise again or repeat until run out of susceptible people

Question 10

describe the epidemic curve of a point source epidemic

Answer 10

large population exposed over a short period of time so high peak at beginning and then tapers off; most common form of transmission for food-borne disease

Question 11

describe the epidemic curve of a continuing common source or intermittent exposure epidemic

Answer 11

several peaks, cannot isolate incubation period

Question 12

give an example of a point source epidemic

Answer 12

legionnaire’s disease

Question 13

give an example of continuing common source or intermittent exposure epidemic

Answer 13

cholera

Question 14

describe the 3 steps in step 4 of investigating an outbreak (calculate attack rates)

Answer 14

1. calculate attack rate for each possible risk factor
2. if there is an obvious commonality for the outbreak, calculate attack rates based on exposure status (a community picnic, then later you can calculate this to individual items at the picnic)
3. if there is no obvious commonality for the outbreak, calculate attack rates based on specific demographic variables

Question 15

describe step 5 of investigating an outbreak (determining source of epidemic)

Answer 15

attack rates can point statistically to the factor most closely associated with becoming a case, but it may require more than one risk factor to become a case, so ask if there are case that are NOT associated with your source (like malaria not from a mosquito)

Question 16

describe 3 things that happen in step 6 of investigating an outbreak (recommending control measures)

Answer 16

1. recommend measures that would serve to reduce transmission (toss potato salad)
2. these recs will be considered by public health personnel
3. then long-term measures will be provided to prevent future outbreaks (here is how to store the potato salad)

Question 17

describe 4 things that happen in step 7 of investigating an outbreak (following up)

Answer 17

1. follow up to determine the effects of the intervention measures incorporated
2. meet with your team to critique and refine your response
3. identify what works well and what did not
4. communicate the specifics on the outbreal for study and educational applications

Question 18

define a foodborne disease outbreak

Answer 18

an incident in which two or more persons experience a similar illness after ingestion of a common food and epidemiologic analysis implicated the food as the source of the illness

Question 19

define intoxication as related to foodborne illness

Answer 19

ingestion of foods with toxicants of certain plants and animals, metabolic products formed and excreted by microbes while they multiply, or poisonous substances introduced during production, processing, transportation, or storage of food

Question 20

define infections as related to foodborne illness

Answer 20

caused by the entrance of pathogenic microbes into the body and the reaction of the body tissues to their presence or to the toxins they generate within the body

Question 21

give 4 rules of thumb, but not laws, related to foodborne illnesses

Answer 21

1. intoxicants are rapid onset, no fever
2. toxins in the stomach produce vomiting
3. toxins in the intestines produce diarrhea
4. infections produce fever

Question 22

what are the 3 types of foodborne contamination? give examples of each

Answer 22

1. physical: glass, metal fragments, dirt, bone
2. chemical: pesticides, cleaning compounds, poisonous metals (lead), additives and preservatives
3. biological: bacteria, virus, fungi, protists, yeast, mold, parasites, insects, rodents, poisonous fish and plants

Question 23

what are the 6 bacterial requirements?

Answer 23

1. food
2. water
3. pH
4. temperature
5. time
6. oxygen

Question 24

what kind of food do most bacteria require?

Answer 24

what we consider to be potentially hazardous food such as milk or milk products, eggs, meat, poulty, fish, shellfish (anything high protein and moist)

Question 25

describe bacterial water requirement

Answer 25

most bacteria require moisture to thrive

Question 26

what is Aw?

Answer 26

water activity: the amount of water available in food

Question 27

what is the lowest Aw where bacteria can grow?

Answer 27

0.85

Question 28

what is the Aw range of most potentially hazardous foods?

Answer 28

0.97-0.99

Question 29

at what pH range do most bacteria grow best?

Answer 29

neutral or slightly acidic (4.6-7.0)

Question 30

what is the danger zone of temperature for foods (where most bacterial growth occurs)?

Answer 30

45-145 degrees F

Question 31

describe how time relates to temperature for bacterial growth in foods

Answer 31

do not let food stay in the danger zone of temperature for more than 4 hours!!!

Question 32

do all bacteria require the same amount of oxygen?

Answer 32

no; can be aerobic, anaerobic, or facultative anaerobes

Question 33

what are the 6 major causes of foodborne disease?

Answer 33

1. improper cooling 2. improper cooking 3. improper reheating 4. improper holding temperature 5. cross contamination 6. infected food handlers, poor employee hygiene