Transcript PowerPoint-Präsentation

Stochastic Simulation of Epidemics
on Large Contact Networks
Markus Schwehm and Martin Eichner
Department of Medical Biometry, University of Tübingen, Germany
Contact Network
Event Model
Network Interface
public interface Network {
public int[] getContacts(int node);
public int getSize();
public double getAverageConnectivity();
public void report();
}
FI
free  isolated
Random
free  isolated
free  traced, quarantine
Abstract Network
Local
FI
FT,Q
Scalefree
Social
ND
DO
ON
none  detectable
detectable  obvious
obvious  none
DB
RS
SE
EI
IR
death  birth
removed  susceptible
susceptible  exposed
exposed  infectious
infectious  removed
Discrete Event Simulator
Individual-based Simulation
The inhabitants of the population are represented
by their internal state (infection, symptom and
contact status) and represent nodes in a contact
network. The modular design allows to exchange
the contact network independent of the chosen
discrete event model. For each individual the
contact network allows to identify a limited
number of contacts for transmission of the
infection or for implementing contact tracing
interventions. Currently there exist parameterized
network generators for
local, global, random and
scalefree contact networks.
Moreover, the data structure allows to maintain
arbitrary networks consisting of several independent
layers. We were able to
simulate populations of two
million individuals on a
personal computer.
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The discrete event simulation distinguishes tree
types of events. The first type implements the
standard SEIRS infection dynamics with
susceptible, exposed, infectious and recovered
states as well as vaccination and a simple
birth/death process. The second type models the
visibility of the disease according to none,
detectable or obvious symptoms. The third type
allows to model intervention strategies (like
contact tracing, quarantine and case isolation),
which influence the contact structure of
individuals. Events can trigger further events for
the same individual and
__
via the contact network for
other
individuals.
All
events are processed in a
discrete event simulator
which is optimized for
large numbers of events
using a priority queue
(indirect heap algorithm)
and can process about
50.000 events per second.
www.ra.informatik.uni-tuebingen.de/mitarb/schwehm/welcome_e.html
www.uni-tuebingen.de/biometry/me_research.html