Lecture 3 8/28/24

Question 1

How can a case be defined?

Answer 1

based on signs, symptoms, epidemiology, and/or performance

Question 2

How are disease patterns described in populations?

Answer 2

by animal characteristic, in space, over time

Question 3

What are the two most common ways of depicting spatial distribution?

Answer 3

-area maps
-simple spot/dot maps

Question 4

Why is it important to characterize disease in populations?

Answer 4

-to describe the current status of the population, as well as changes over time
-to make comparisons between groups over time
-to establish cause and identify possible preventive measures

Question 5

What are the different patterns of disease?

Answer 5

-sporadic
-endemic
-outbreak/epidemic
-pandemic

Question 6

What is a sporadic disease?

Answer 6

occurs infrequently with no discernable pattern

Question 7

What is an endemic disease?

Answer 7

occurs with a predictable pattern and has a constant presence

Question 8

What is an epidemic disease?

Answer 8

significantly more disease than usual, with no predictable pattern

Question 9

What is a pandemic disease?

Answer 9

epidemic affecting a number of countries

Question 10

What does a sporadic disease pattern potentially suggest about the causative agent?

Answer 10

-causative agent infrequently infects the host
-causative agent is usually present, but other factors are required for clinical disease to develop

Question 11

What is endemic disease the result of?

Answer 11

a predictable and often long-term balance between agent and host

Question 12

Why is the word outbreak used instead of epidemic?

Answer 12

-outbreak draws less media attention and is perceived as less frightening
-often used with food related illnesses

Question 13

How does an outbreak differ from an epidemic?

Answer 13

-outbreak is any occurrence of disease at a higher rate than expected, but is relative
-epidemic is occurrence of disease in which the frequency of disease during a time interval is clearly in excess of expected frequency

Question 14

What is an epidemic curve?

Answer 14

graph of the number of new cases over time, which provides information about how disease is spreading in the population

Question 15

Which two values are key to the construction of an epidemic curve?

Answer 15

-time of disease
-frequency of disease

Question 16

Which factors impact the shape of an epidemic curve?

Answer 16

-incubation period
-infectivity
-proportion of susceptible hosts in the population

Question 17

What is a minimum/threshold density?

Answer 17

the number of susceptible animals required to allow contact-transmitted epidemic to commence

Question 18

What is a point source epidemic?

Answer 18

epidemic in which there is a rapid onset of disease cases, indicating a common source

Question 19

What is a propagated epidemic?

Answer 19

epidemic in which there is a slower onset of cases with a build up over time, indicating animal-to-animal transmission

Question 20

What are the characteristics of a point source epidemic?

Answer 20

-common source
-usually needs a vehicle
-skews epidemic curve to the right

Question 21

What are the characteristics of a propagating epidemic?

Answer 21

-animal to animal transmission
-usually spread by hosts and/or vectors
-epidemic curve skews to the left

Question 22

What are the defining characteristics of a pandemic?

Answer 22

-epidemic affecting multiple countries
-disease must be infectious

Question 23

What are the components of the WHO definition of a human pandemic?

Answer 23

-emergence of disease new to a population
-agent infects humans and causes serious illness
-agent spreads easily and sustainably among humans

Question 24

How does the pattern of disease change with time and a stable environment?

Answer 24

starts as epidemic before transitioning to endemic and eventually sporadic