Epidemiology: The SEIR model: Difference between revisions
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The lines in the JSXGraph-simulation below have the following meaning: | The lines in the JSXGraph-simulation below have the following meaning: | ||
* <span style="color:Blue">Blue: Rate of susceptible population</span> | * <span style="color:Blue">Blue: Rate of susceptible population</span> | ||
* <span style="color: | * <span style="color:black">Black: Rate of exposed population</span> | ||
* <span style="color:red">Red: Rate of infectious population</span> | * <span style="color:red">Red: Rate of infectious population</span> | ||
* <span style="color:green">Green: Rate of recovered population (which means: immune, isolated or dead) | * <span style="color:green">Green: Rate of recovered population (which means: immune, isolated or dead) | ||
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var S = brd.createElement('turtle',[],{strokeColor:'blue',strokeWidth:3}); | var S = brd.createElement('turtle',[],{strokeColor:'blue',strokeWidth:3}); | ||
var E = brd.createElement('turtle',[],{strokeColor:' | var E = brd.createElement('turtle',[],{strokeColor:'black',strokeWidth:3}); | ||
var I = brd.createElement('turtle',[],{strokeColor:'red',strokeWidth:3}); | var I = brd.createElement('turtle',[],{strokeColor:'red',strokeWidth:3}); | ||
var R = brd.createElement('turtle',[],{strokeColor:'green',strokeWidth:3}); | var R = brd.createElement('turtle',[],{strokeColor:'green',strokeWidth:3}); | ||
Revision as of 08:04, 27 April 2009
For many important infections there is a significant period of time during which the individual has been infected but is not yet infectious himself. During this latent period the individual is in compartment E (for exposed).
Assuming that the period of staying in the latent state is a random variable with exponential distribution with parameter a (i.e. the average latent period is [math]\displaystyle{ a^{-1} }[/math]), and also assuming the presence of vital dynamics with birth rate equal to death rate, we have the model:
- [math]\displaystyle{ \frac{dS}{dt} = \mu N - \mu S - \beta \frac{I}{N} S }[/math]
- [math]\displaystyle{ \frac{dE}{dt} = \beta \frac{I}{N} S - (\mu +a ) E }[/math]
- [math]\displaystyle{ \frac{dI}{dt} = a E - (\gamma +\mu ) I }[/math]
- [math]\displaystyle{ \frac{dR}{dt} = \gamma I - \mu R. }[/math]
Of course, we have that [math]\displaystyle{ S+E+I+R=N }[/math].
The lines in the JSXGraph-simulation below have the following meaning:
* Blue: Rate of susceptible population * Black: Rate of exposed population * Red: Rate of infectious population * Green: Rate of recovered population (which means: immune, isolated or dead)
