Unit 08: Surveillance and Outbreak Investigation

Question 1

What is epidemiologic surveillance?

Answer 1

the ongoing systematic collection, analysis, and interpretation of health data essential to the planning, implementation, and evaluation of public health practice closely integrated with the timely dissemination of these data to those who need to know.

Question 2

What are the two types of surveillance?

Answer 2

1. Passive surveillance
2. Active surveillance

Question 3

What is Passive surveillance?

Answer 3

• surveillance in which available data on reportable diseases are used, or in which disease reporting is mandated or requested by the government or the local health authority, with the responsibility for the reporting often falling on the health care provider or district health officer.

Question 4

What is Active surveillance?

Answer 4

• a system in which project staff are specifically recruited to carry out a surveillance program.
• make periodic field visits to health care facilities such as clinics, primary health care centers, and hospitals in order to identify new cases of a disease or diseases or deaths from the disease that have occurred (case finding ).

Question 5

What are the two Surveillance Data Collection Methods?

Answer 5

1. Passive Data Collection
2. Active Data Collection

Question 6

What is Passive Data Collection?

Answer 6

Data are acquired from other primary sources and have been derived for other purposes.

Question 7

What is Active Data Collection?

Answer 7

Data is actively searched for and collected for the goal of surveillance. (targeted surveillance activities.)

Question 8

What is Lab-based Surveillance?

Answer 8

relies on data produced in clinical, and public health labs, which are often responsible for confirming new cases of infectious disease.

Question 9

What is Sentinel Surveillance?

Answer 9

collects in-depth data (which would not be feasible at a national or provincial level) with the hope that the results are representative of the broader population.

Question 10

What is Syndromic Surveillance?

Answer 10

uses individual and population health indicators that are available before confirmed diagnoses or laboratory confirmation to identify outbreaks or health events and monitor the health status of a community.

Question 11

What is Social Media Surveillance?

Answer 11

monitors trends on popular Internet and social media sites (i.e., Google searches, Facebook, Twitter). More specifically, they look at common words, terms and/or phrases that provide a measure of illness (e.g., “flu,” “diarrhea,” and “cough,” etc.).

Question 12

What are the 4 main issues with surveillance?

Answer 12

1. underreporting
2. lack of denominator data
3. false alarms
4. other issues (slow, inefficient, etc.)

Question 13

What is an Outbreak?

Answer 13

an increase, often sudden, in cases of disease above what is expected in the population.

Question 14

What are the two methods of detecting an outbreak?

Answer 14

1. Community-identified (Illness is reported by individuals, physicians or others to public health authorities.)
2. Lab-identified (Ongoing surveillance of lab isolates by health departments is performed to determine if the observed number of cases exceeds the expected level. Labs also monitor for unusual or rare strains of common pathogens.)

Question 15

what is a case definition?

Answer 15

a standard set of criteria for deciding whether an individual should be classified as having the condition of interest.

Question 16

What are the steps of outbreak investigation? (10)

Answer 16

1. Determine the existence of an outbreak.
2. Confirm the diagnosis.
3. Prepare for field and assemble team.
4. Implement immediate control measures.
5. Define a case and case-finding.
6. Describe data by time, place and person.
7. Develop a hypothesis.
8. Test hypothesis – implement studies.
9. Implement prevention and control measures.
10. Disseminate findings, conduct evaluation.

Question 17

What is a point source outbreak? What does the graph look like?

Answer 17

• Individuals are exposed over a relatively short period of time.
• Everyone becomes ill at the end of one incubation period.
• The epidemic curve (graph of number of cases by day) has a steep upslope and a more gradual down-slope

Question 18

what is an Intermittent Source outbreak? What does the graph look like?

Answer 18

• Individuals may be exposed over days, weeks, or longer.
• The epidemic curve has a pattern that reflects the intermittent nature of the exposure.

Question 19

What is a
Continuous Source outbreak? What does the graph look like?

Answer 19

• Individuals may be exposed over days, weeks, or longer.
• The epidemic curve may have smaller and wider peaks.
• This is somewhat similar to intermittent source, except this source is available continuously, resulting in few gaps in the epidemic curve.

Question 20

What is a Propagated Outbreak? What does the graph look like?

Answer 20

• disease generally spreads slowly and results from person-to-person or animal to animal spread.
• Cases occur over more than one incubation period.
• Results from direct contact, vehicle-borne (e.g., hepatitis B spread by sharing needles), or vector-borne (e.g., yellow fever spread by mosquitoes) modes.
• Duration is generally longer than any of the common source outbreaks, with fairly distinct incubation periods in the epidemic curve

Question 21

when dealing with an outbreak, what are the three methods of testing your hypothesis?

Answer 21

1. Conduct an Epidemiological Study: conduct a retrospective cohort study or a case-control study.
2. Conduct a Trace-Back, Trace-Forward Exercise: Trace-back refers to walking through the steps from the place that the outcome occurred to the point of origin. Trace-forward refers to doing the opposite, where we would start at the point of origin of the item and move forward.
3. Perform an Environmental Investigation: investigators are collecting samples from food, surfaces (e.g., equipment, houses) and environment (e.g., air, water, soil). Samples are then submitted for microbiological and chemical testing. investigators also look into the use of standard practices/standard operating procedures.