  The origin of the unusual incubation period distribution in the development
of AIDS is largely unresolved. A key factor in understanding the observed
distribution of latency periods, as well as the occurrence of infected
individuals not developing AIDS at all, is the dynamics of the long lasting
struggle between HIV and the immune system. Using a computer simulation, we
study the diversification of viral genomes under mutation and the selective
pressure of the immune system.In common infections vast spreading of viral
genomes usually does not takes place. In the case of an HIV infection this may
occur, as the virus successively weakens the immune system by depletion of CD4+
cells.In a sequence space framework, this leads to a dynamically induced
percolation transition, corresponding to the onset of AIDS. As a result, we
obtain the prolongated shape of the incubation period distribution, as well as
a finite fraction of non-progressors that do not develop AIDS, comparing well
with results from recent clinical research.
