S1 - Networks and Dynamics

Question 1

Define dynamics.

Answer 1

How we describe infectious disease movements, patterns, and behaviors over time and geography

Question 2

Define system.

Answer 2

Any group of interacting parts that form a whole

Question 3

Define a complicated system.

Answer 3

Has many interacting parts that need to work correctly in a sequence to reach the desired result. However, each step of the process is completely predictable based on the step before it

Question 4

Define the results of a complex system. Can we easily predict them?

Answer 4

No, the results brought about by the interacting parts of a complex system are not directly predictable

Question 5

Define emergent properties.

Answer 5

Behaviors or outputs of a system that arise from two or more interacting components that cannot be explained by either of them on their own

Question 6

What is an epidemic curve?

Answer 6

A graph of the number of cases or incidence rate of cases versus time.

Question 7

Define propagate.

Answer 7

To travel

Question 8

What is human ecology?

Answer 8

How humans interact with and are impacted by their surrounding environment and each other

Question 9

What is a node?

Answer 9

An individual entity in the network, like a person or a hospital

Question 10

What is an edge (In relation to a node)?

Answer 10

What connects two nodes

Question 11

What is a random network?

Answer 11

A lot of people/things randomly connected to each other with no rhyme or reason

Question 12

What is a scale-free network?

Answer 12

A network where some nodes are more highly connected than others

Question 13

What are network hubs?

Answer 13

Nodes that are more connected than others

Question 14

What is synchronous spread?

Answer 14

The timing of an epidemic overlapping in multiple locations

Question 15

What is (sexual) concurrency?

Answer 15

Individuals having multiple partners at the same time

Question 16

What is compartmental flow?

Answer 16

We are essentially coming up with a fake scenario in which people flow from one “compartment” or stage to another

Question 17

Describe a deterministic model.

Answer 17

The model does not worry about random effects, like individual differences in susceptibility. Everyone follows the same rules of probability about what compartment they are in at any given time.

Question 18

Describe the SIR model.

Answer 18

“Susceptible, Infectious, and Recovered.” Each person is either in the S, I or R compartment at any given time. The simplest version of the SIR model doesn’t take into account birth and death.

Question 19

What is the S in the SIR model?

Answer 19

Susceptible individuals (May become sick)

Question 20

What is the I in the SIR model?

Answer 20

Infectious individuals (Are sick and may infect others)

Question 21

What is the R in the SIR model?

Answer 21

Recovered individuals (Are no longer in danger of becoming sick again)

Question 22

Describe a stochastic model.

Answer 22

A model that takes individuality into account. They are very commonly used and based off of the same mathematical principles as deterministic models. They just use more complicated probability formulas describing whether someone will move into the next compartment, and are not deterministic.

Question 23

What is an agent-based model?

Answer 23

Helpful to study diseases that are very difficult to trace through a network to a particular infecting person (like respiratory diseases). They use computer simulations to estimate the behaviors of a real-world city, region or country. The simulations can help predict what emergent properties might occur as an infectious disease travels.

Question 24

What is R0?

Answer 24

The number of infected individuals one person is expected to infect while they are infectious

Question 25

What is the herd-immunity threshold?

Answer 25

The proportion of people that need to be immunized in order to eradicate a disease, or prevent an outbreak (Varies from disease to disease)

Question 26

What is hysteresis?

Answer 26

A change in status. ex. a new emerging disease can cause an epidemic, and if not eliminated, reach a new stable equilibrium where it is now endemic

Question 27

How do we calculate the number of people that will move from the S compartment to the I compartment?

Answer 27

cBSI/n

c = contacts
Beta = P(Infected/contacted)
S = susceptible
I = infected
n = population

Question 28

How do we calculate the number of people moving from the I compartment to the R compartment?

Answer 28

1/DI

D = duration
I = Infectious

Question 29

What is Rt?

Answer 29

Real-time or effective reproduction. Our goal when trying to prevent infectious diseases is to push Rt below 1, so that the epidemic will die out. In essence, you want to “remove” susceptible or infectious individuals from the population faster than the disease spreads. Vaccines do this very effectively

Question 30

What is the formula for R0?

Answer 30

cB/y

c = contact
B = P(Infected/contacted)
y = rate of recovery

Question 31

What is our R0 goal?

Answer 31

R0 < 1 (The disease is not actively propagating)

Question 32

What is the E in the S(E)IR system?

Answer 32

Exposed

Question 33

What are agent-based models used for?

Answer 33

Predictions

Question 34

Selective mixing is a trend of what kind of network?

Answer 34

Sexual networks