This paper analyses the relationship between El Nino-Southern Osicillation (ENSO) events and Ross River virus (RRv) disease in different spatial scales (eg, local government areas, Queensland state and Australia). Information on RRv cases was supplied by the Queensland Department of Health (for the period of 1 January 1985-31 December 2001) and the Commonwealth Department of Health and Ageing (for the period of 1 January 1992-31 December 2001). Data on the ENSO were supplied by the Australian Bureau of Meteorology. Spearman's rank correlation analysis was conducted on the monthly ENSO and monthly incidence of RRv disease. The function of cross-correlation was used to show the correlation between ENSO and RRv disease at different time lags. No statistically significant relationship was found between the monthly index of ENSO and monthly incidence of RRv disease in whole Queensland (rs = -0.06; p = 0.40) and Australia (rs = -0.004; p = 0.69). However, there were significant relationships between ENSO and RRv disease in mid coastal areas, especially Mackay (rs = -0.20, p < 0.01) and Rockhampton (rs = -0.18, p < 0.05) in Queensland. The results of this study show that the ENSO was associated with RRv transmission in specific areas but not large geographic regions. The reasons for this will be explored in the paper.
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