S1 - Networks and Dynamics Flashcards
Define dynamics.
How we describe infectious disease movements, patterns, and behaviors over time and geography
Define system.
Any group of interacting parts that form a whole
Define a complicated system.
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
Define the results of a complex system. Can we easily predict them?
No, the results brought about by the interacting parts of a complex system are not directly predictable
Define emergent properties.
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
What is an epidemic curve?
A graph of the number of cases or incidence rate of cases versus time.
Define propagate.
To travel
What is human ecology?
How humans interact with and are impacted by their surrounding environment and each other
What is a node?
An individual entity in the network, like a person or a hospital
What is an edge (In relation to a node)?
What connects two nodes
What is a random network?
A lot of people/things randomly connected to each other with no rhyme or reason
What is a scale-free network?
A network where some nodes are more highly connected than others
What are network hubs?
Nodes that are more connected than others
What is synchronous spread?
The timing of an epidemic overlapping in multiple locations
What is (sexual) concurrency?
Individuals having multiple partners at the same time
What is compartmental flow?
We are essentially coming up with a fake scenario in which people flow from one “compartment” or stage to another
Describe a deterministic model.
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.
Describe the SIR model.
“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.
What is the S in the SIR model?
Susceptible individuals (May become sick)
What is the I in the SIR model?
Infectious individuals (Are sick and may infect others)
What is the R in the SIR model?
Recovered individuals (Are no longer in danger of becoming sick again)
Describe a stochastic model.
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.
What is an agent-based model?
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.
What is R0?
The number of infected individuals one person is expected to infect while they are infectious
What is the herd-immunity threshold?
The proportion of people that need to be immunized in order to eradicate a disease, or prevent an outbreak (Varies from disease to disease)
What is hysteresis?
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
How do we calculate the number of people that will move from the S compartment to the I compartment?
cBSI/n
c = contacts Beta = P(Infected/contacted) S = susceptible I = infected n = population
How do we calculate the number of people moving from the I compartment to the R compartment?
1/DI
D = duration I = Infectious
What is Rt?
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
What is the formula for R0?
cB/y
c = contact B = P(Infected/contacted) y = rate of recovery
What is our R0 goal?
R0 < 1 (The disease is not actively propagating)
What is the E in the S(E)IR system?
Exposed
What are agent-based models used for?
Predictions
Selective mixing is a trend of what kind of network?
Sexual networks
