patterns of disease epidemics

Question 1

what are the 4 patterns in population?

Answer 1

sporadic
endemic
epidemic
pandemic

Question 2

sporadic pattern of disease

Answer 2

no discernible pattern, rare cases

Question 3

endemic pattern of disease

Answer 3

predictable pattern and commonly present

result of balance between agent and host

Question 4

epidemic pattern of disease

Answer 4

more disease than usual

Question 5

pandemic pattern of disease

Answer 5

epidemic affecting many countries

Question 6

what is the epidemiology curve used for?

Answer 6

used to describe epidemic and develop hypotheses

Question 7

what is point-source epidemic?

Answer 7

rapid onset, most cases within range of incubation period, suggestive of common but not contagious source (i.e. contaminated food or water)

Question 8

what is propagating epidemic?

Answer 8

slower onset with buildup in number of cases - suggests animal-to-animal spread (transmissible)

Question 9

what are the three patterns of disease over time?

Answer 9

seasonal
cyclical
secular

Question 10

season pattern of disease

Answer 10

periodicity of 1 year or less

due to direct or indirect affect of climate/weather (environment) on agent or host, or due to human activities

Question 11

cyclical pattern of disease

Answer 11

periodically over 2.5-5 years

over time naive animals are born into the herd and % susceptibility increases

Question 12

secular pattern of disease

Answer 12

periodicity of many years or decades

reintroduction of pathogen or mutation of agent

Question 13

patterns in space

Answer 13

John Snow

• special distribution of disease (risk factors)
• environmental or mad-made differences between location

Question 14

what are the 4 patterns of disease by cohort (i.e. age)

Answer 14

• linear
• U-shaped
• curvilinear
• multi-nodal

Question 15

linear pattern of disease by cohort

Answer 15

increase risk with age

Question 16

U-shaped pattern of disease by cohort

Answer 16

higher risk in young and geriatric

Question 17

curvilinear pattern of disease by cohort

Answer 17

higher risk in middle aged (growing or mature) population

Question 18

multi-nodal pattern of disease by cohort

Answer 18

differential expression by age of same agent

Question 19

why does the number of new cases go down in a propagating epidemic?

Answer 19

because there are no new susceptible animals

-they either die, recover or are immune

Question 20

point-source outbreaks cases are associated with what?

Answer 20

initial introduction

Question 21

propagating outbreaks appear when?

Answer 21

once it starts to spread in the population

-secondary and tertiary cases

Question 22

when percent (%) susceptibility reaches a threshold, what occurs?

Answer 22

disease outbreak

Question 23

linear pattern disease examples

Answer 23

arthritis

cancer

Question 24

U-shaped pattern disease examples

Answer 24

influenza (affects youngest and oldest

Question 25

curvilinear disease pattern examples

Answer 25

reproductive diseases

production diseases

Question 26

multi-nodal pattern disease examples

Answer 26

IBD in cattle