Each red blood cell infected by Plasmodium displays one variant surface protein at a time, chosen from a large var gene family. The immune system learns to recognise whichever variant currently dominates the infected population, then ramps up antibody "titer" against it and starts clearing those cells.
With switching on, a fraction of infected cells periodically flip to a different variant (visible as a colour pop). Every time the dominant colour changes, the immune system has to re-learn its target and the titer resets — so it rarely finishes ramping before the population has already moved on. Growth from parasite replication keeps outrunning the chase, and total infection never reaches zero.
With switching off, every cell is locked to the same variant forever. The immune system locks onto it once, titer ramps all the way to maximum, and the kill rate eventually exceeds growth — the infection is cleared completely.
titer(t) → 1 while dominant is stable
kill = titer · killStrength (applied only to targeted variant)
switch event: reassign fraction f of cells → random new variant
- Growth rate — how fast infected cells replicate into new infected cells.
- Switch interval / fraction — how often, and how much of the population, undergoes a var-gene switching event.
- Immune kill strength — the maximum clearance rate once antibody titer against the current target has fully ramped up.