Graphical representation of the <i>SI</i>_<i>X</i><i>I</i>_<i>E</i><i>R</i>_<i>N</i><i>R</i>_<i>LTR</i> model.

<p>The circles represent compartments; the arrows represent transition rates between the compartments. Upon infection with a retrovirus, susceptible individuals (S compartment) transition to the I_X compartment. If immunity is easily acquired to the retroviral infection, individuals enter the R_N compartment; they have recovered without integration of the retrovirus, and the offspring of these individuals enter the susceptible compartment. If it is difficult for immunity to arise to the retrovirus, then integration of the retrovirus into the germline of these I_X individuals may occur, and the offspring of these individuals enter the I_E compartment. After the threat of the retroviral infection has passed, the integration is free to be lost to recombinational deletion (or mutation), and individuals enter the R_LTR compartment.