Epidemic curve and hazard function for occurrence of clinical equine influenza in a closed population of horses at a 3-day event in southern Queensland, Australia, 2007.

The risk of individuals becoming infected during an epidemic of infectious disease can vary as the disease progresses. Monitoring this risk may provide information about the dynamics of transmission. This study describes the epidemic curve for an epidemic of equine influenza (EI) in a closed population of horses predominantly immunologically naïve to EI at a 3-day event at Morgan Park in southern Queensland, Australia. The hazard function suggested that a subset of horses were at reduced risk of becoming infected. This highlights the importance, when modelling infectious disease in populations, of considering possible differences in the risk of infection among subgroups in the population.