Influenza is one of the most common infectious diseases in the world. It causes considerable morbidity and mortality each year. There have been 31 documented influenza pandemics including three pandemics during the twentieth century (1918, 1957 and 1969). However, the cause of these pandemic cycles has remained largely unknown. We have found a significant association between the incidence of influenza and El Niño/Southern Oscillation (ENSO), and suggest that the pandemic cycles may be mediated by the climate pattern brought to Australia by ENSO. We quantify the relationship between the ENSO index and the monthly incidence of notified influenza infections in Australia. Poisson auto-regression time series model was conducted using data collected for the period of 1 January 2001–31 December 2002 supplied by Commonwealth Department of Health and Ageing and the Australian Bureau of Meteorology. The results showed that there was a significant association between the monthly incidence of the influenza and the monthly index of ENSO (β = −0.11, p < 0.01). The findings suggest that the ENSO warrant further investigation as a mediator/predictor of the influenza pandemic cycles.
School of Public Health, Queensland University of Technology