BIOL 437 Week Five Part 2

Question 1

stable endemicity

Answer 1

• relatively stable incidence of infection or disease

eg. HIV

Question 2

seasonal endemicity

Answer 2

• some waterborne and respiratory infections

eg. cholera, seasonal influenza

Question 3

immunizing infections

Answer 3

• recurrent outbreaks with predictable inter epidemic periods
  ex. measles, whooping cough

Question 4

pathogen characteristics that result in population cycles

Answer 4

• high transmissibility
• short infectious period
• transmission-blocking immunity upon recovering

Question 5

epidemic will not occur until

Answer 5

-enough new susceptible individuals are born

Question 6

inter-epidemic period determined by

Answer 6

-birth rate of host
-transmission rate of pathogen
*vaccination reduces number of sustceptible individuals born into a population
>mass vaccination will increase the inter-epidemic period

Question 7

seasonality

Answer 7

1. Environmentally-forced disease dynamics
2. Term-time forcing
3. Behaviourally associated

Question 8

environmentally forced disease

Answer 8

-winter peak in influenza
>time of year depnds on hemisphere
-vector borne infections
-water-borne infections

Question 9

term-time forcing

Answer 9

• seasonal changes in contacts amon hosts
• increase contact between school age children
  ex. whooping cough

Question 10

behaviourally associated

Answer 10

-urban-rural seasonal migration
>low contact during wet season: rural
>higher contact rate during dry season: work in urban settings
ex. measles

Question 11

host diversity

Answer 11

-ex. chicken pox
-persistant mechanism within individual host
>dormant in NS, re-emerges when host is an adult as shingles
>respiratory transmission and direct contact with rash

Question 12

host range

Answer 12

• ex. rabies vaccine
• wide
• high affinity for nervous tissue

Question 13

for infection to spread

Answer 13

-average number of new infetions is greater than or equal to old infections

Question 14

for infection to persist

Answer 14

-necessary for at least one infected individual to pass that onward

Question 15

larger populations

Answer 15

-have more opportunity for transmission

Question 16

critical community size

Answer 16

• population size where transmission of a specific pathogen is a certainty
• smallest population size for which a given population does NOT go extinct

Question 17

vaccination and effective community size

Answer 17

-vaccination reduces it

>reduces number of susceptibles

Question 18

probability of extinction before a major epidemic

Answer 18

-equal to rate of recovery divided by transmission rate

Question 19

pathogen microbe interactions

Answer 19

-ex. Bordetella: whooping and kennel cough
-whooping cough is only humans
>absence of Type VI secretion system

Question 20

social network

Answer 20

• network of people connected by potential disease transmission events
• create maps
• important for contact tracing
• road maps for spread of infectious disease

Question 21

nodes

Answer 21

-hosts

Question 22

edges between nodes

Answer 22

-potential disease transmission events

Question 23

degree distribution

Answer 23

• of a node is the number of edges it has
• number of contacts the person has
• affects R.

Question 24

variance in degree distribution

Answer 24

-greatly affected by R.
>some will have more or less contacts than average
-higher R. in high variance network

Question 25

superspreaders

Answer 25

• generate a higher number of secondary cases
• particulary long infectious period
• shed a large number of the pathogen
• large number of contacts

Question 26

rural

Answer 26

-new human pathogens emergence

Question 27

urban

Answer 27

-reserviours for established human pathogens
-chain of transmission is strong
>increased contact rates
>supply of susceptibles

Question 28

island-mainland metapopulation dynamics

Answer 28

• group of location populations connected by infrequent movement between them
• susceptible populations increase in smaller communities

Question 29

metapopulations persistance

Answer 29

• larger areas allow for diseases to persist

- spatial waves of spread

Question 30

movement/transportation

Answer 30

• waves of Europeans brought many diseases
• wiped out original inhabitants
• now we can travel places within hours

Question 31

co-infection consequences

Answer 31

• hosts already infected by one pathogen may be more susceptible to other pathogens
• second pathogen may trigger worse infection
• interfer with vaccination or treatment
• promote super-shedders