Early 2009 saw the emergence of an H1N1 influenza epidemic in North America that eventually spread to become the first pandemic of the twenty-first century. Previous work has suggested that pandemics and near-pandemics can have large macroeconomic effects on highly affected regions; here, we estimate what those effects might be for Australia. Our analysis applies the MONASH-Health model: a computable general equilibrium model of the Australian economy. We deviate from previous work by incorporating two important short-run mechanisms in our analytical framework: quarterly periodicity and excess capacity. The analysis supports the assertion that an H1N1 epidemic could have significant short-run macroeconomic effects but the size of these effects is highly dependent on the degree of inertia in the markets for physical capital and labour.