Lecture 4

Question 1

What is the most dangerous period that can lead to an outbreak? (uninterrupted transmission)

Answer 1

Btwn end of latent period & symptomatic period

Question 2

isolation vs quarantine

Answer 2

Isolation
• separate CASES from susceptible during communicable period

Quarantine
• Separate HEALTHY individual following contact w/ cases –minimum of 1 incubation period

Question 3

Dz control

Answer 3

1. ↓ shedding
2. ↓ duration of environmental survival
3. ↓ vector population
4. ↓ exposure to infected host
   - Quarantine / isolation

Question 4

Heard immunity

Answer 4

• resistance of group to invasion/spread of infectious agent
  • based on proportion of resistant individuals
• Mass immunization
  • controls dz by vax large segments of population
  • Dynamics of transmission altered
  • 70-80% vx’d – good

Question 5

Outbreak

Answer 5

↑ in incidence of dz above normal

• synonymous w/ EPIDEMIC

Question 6

Level of dz occurrence:
• Sporadic
• Endemic
• Epidemic
• Pandemic

Answer 6

Sporadic
  • Rare / irregular cases
  • not predictable
Endemic
   • Stable state
   • predictable 
Epidemic
   • In excess of the executed level ( > endemic)
Pandemic
   • Widespread epidemic affecting large portion of population 
   • many countries

Question 7

If there is an ↑ in cases (above normal), be sure the changes are not due to:

Answer 7

1. Method of dx
2. awareness & case reporting
3. Case definition

Question 8

How can case definition affect # of cases?

Answer 8

Definition usually becomes more restricted over time

Question 9

Epidemic curve

Answer 9

• # of incident cases VS time
• Overall shape of the curve reveals the type of outbreak
Info about: 
  - Pattern
  - Magnitude
  - Time trend

Question 10

Types of outbreaks

Answer 10

• Common source
- Point Source – sharp ↑
- Continuous –no peak
• Propagated – multiple peaks

Question 11

Using the propagated epidemic curve, what does the peak-to-peak interval tell you?

Answer 11

estimated incubation pd

Question 12

How are line listings helpful?

Answer 12

• Compare temporal & spacial relationships of healthy/sick

* evaluate of distribution of dz w/ respect to host characteristics

Question 13

Attack Rate equation

Answer 13

sick / Total

Question 14

Attack Rate Ratio

Answer 14

AR exposed / AR unexposed

• • tells us Tx is XXX more likely to become ill
• • if no difference in groups – ARR = 1

Question 15

Control implementation to shorten epidemic period & protect healthy

Answer 15

• Separate carriers
• Vx susceptible
• Remove agent
• Remove reservoir

Question 16

Steps in Outbreak investigation

Answer 16

1. Confirm that there is an outbreak
2. Formulate case definition
3. Isolate and survey known cases
4. Characterize the outbreak in space and time
5. Formulate/test/revise/retest hypothesis
6. Implementation of control measures
7. Disseminate results