As mentioned in the previous section, ILI is one of the sources of drug wastage. It represents other types of illnesses as well as non-pandemic seasonal influenza, and is symptomatically indistinguishable from the pandemic strain. For these patients, they will be directed to the designated flu centre for diagnosis and treatment. Without proper diagnoses, these patients will consume resources unnecessarily. Since ILIs are non-specific illnesses, we assumed the number of new ILI cases to surface at a constant rate, independent from the spread of pandemic influenza. Variations due to seasonal effects are currently beyond the scope of this work. Based on published data from the Ministry of Health, Singapore (Ministry of Health Singapore 2006b), we estimated the rate to be three new infections per day, each lasting for 72 h. In the model, these individuals are randomly selected from the ILI-susceptible population; those suffering from pandemic flu and ONILIs can still be inflicted by ILIs. For ONILIs, we estimated the daily new occurrences to be 45 people (Ministry of Health Singapore 2006a), and they are randomly selected from the ONILI-susceptible population. Again, each ONILI case is assumed to last for 72 h. For details on how the values are derived, refer to the electronic supplementary material.