To simulate the Ww0 scenario in Figure 1 (which corresponds to antigenic drift in the SE Asia region) requires rapid strain growth rates (r large). This is done by initially allowing the total population (of all strains) to grow rapidly. Once the supply of susceptibles becomes depleted the population collapses abruptly (resource availability variable). The supply of susceptibles is then re-instated and the boom-bust cycle repeats itself. New strain variants are generated through the cycle. The purpose of this is to mimic the conditions for emergence of new variants when there is competition and growth. In this scenario variants that compete against each other are not at equilibrium in the population so we are addressing a localised competitive situation. The total population size used for this simulation was 10,000 individuals with d(x)~a with a in the range +0:1 with a mutation rate of 10 {5 day -1 .