Epidemiology and Surveillance

Question 1

Case definition

Answer 1

Person who fulfils a set criteria to be defined as having the disease

Question 2

Suspected case

Answer 2

Possible/probable/laboratory confirmed case

Question 3

Index case

Answer 3

First person who was found with the disease

Question 4

Contact

Answer 4

Anyone who has been in contact with a case

Question 5

Case fatality rate

Answer 5

Proportion of deaths among confirmed cases of the disease for a time period

Question 6

Disease mortality rate

Answer 6

The number of deaths due to a specific disease in a particular population (per unit of time)

Question 7

Infectious dose

Answer 7

Quantity of microorganism needed to produce infection in a host

Question 8

Attack rate

Answer 8

Proportion of exposed persons who have become infected

Question 9

Virulence

Answer 9

Proportion of people who develop the disease and become severely ill

Question 10

Outbreak

Answer 10

Two or more cases of disease that are linked OR occurrence of disease not expected in the area

Question 11

Common source outbreak

Answer 11

Group exposed to common source of infectious agent/toxin e.g. school, restaurant

Question 12

Point source outbreak

Answer 12

Exposure to infectious agent has occurred over a brief period of time

Question 13

Propagated outbreak

Answer 13

Outbreak is gradually spreading from person to person

Question 14

Endemic

Answer 14

Persistent levels of disease occurrence

Question 15

Hyper-endemic

Answer 15

Persistently high levels of disease occurrence

Question 16

Epidemic

Answer 16

Occurrence within an area in excess of what is expected for a given time period/widespread community transmission

Question 17

Pandemic

Answer 17

Epidemic widespread over several countries

Question 18

R0 - basic reproduction number

Answer 18

How many people the infected person infects

Question 19

R - effective reproduction number

Answer 19

Considers the real world e.g. preventative measures and life-long immunity

Question 20

What is surveillance?

Answer 20

Systemic, ongoing, regular data collection

Question 21

What does surveillance do?

Answer 21

Detects change by gathering timely feedback for action

Question 22

What are the steps involved in surveillance?

Answer 22

1) Collect data
2) Identify data sources
3) Analyse data
4) Response

Question 23

Limitation of surveillance?

Answer 23

Rarely measures disease incidence 
Small changes in disease may not be picked up 
Ecological fallacy 
Susceptible to bias 
Incomplete data 
Needs contextual information

Question 24

Passive surveillance

Answer 24

Most common type
Degree of incompleteness/low sensitivity
Cheap, good for measuring trends over time, easy to implement
e.g. routine laboratory notification

Question 25

Sentinel surveillance

Answer 25

Sample surveillance from sentinel sources Works well for common diseases but misses rare conditions Requires for time and resources than passive If well designed can identify outbreaks quickly May not be representative of wider population

Question 26

Active surveillance

Answer 26

Used when completeness of reporting is required Good for rare or serious conditions Used when public health intervention is required Requires money, resources and people

Question 27

Enhanced surveillance

Answer 27

Type of active surveillance | Usually limited to a specific area, time period and disease type