Climate variability and Ross River virus transmission in Townsville Region, Australia, 1985-1996

BACKGROUND: How climate variability affects the transmission of infectious diseases at a regional level remains unclear. We assess the impact of climate variation on the Ross River virus (RRv) transmission in the Townsville region, Queensland, north-east Australia. METHODS: We obtained population-based information on monthly variations in RRv cases, climatic factors, sea level, and population growth between 1985 and 1996. Cross-correlations were computed for a series of associations between climate variables (rainfall, maximum temperature, minimum temperature, relative humidity and high tide) and the monthly incidence of RRv disease over a range of time lags. We assessed the impact of climate variability on RRv transmission using the seasonal auto-regressive integrated moving average (SARIMA) model. RESULTS: There were significant correlations of the monthly incidence of RRv to rainfall, maximum temperature, minimum temperature and relative humidity, all at a lag of 2 months, and high tide in the current month. The results of SARIMA models show that monthly average rainfall (β = 0.0007, P = 0.01) and high tide (β = 0.0089, P = 0.04) were significantly associated with RRv transmission and maximum temperature was also marginally significantly associated with monthly incidence of RRv (β = 0.0412, P = 0.07), although relative humidity did not seem to have played an important role in the Townsville region. CONCLUSIONS: Rainfall, high tide and maximum temperature were likely to be key determinants of RRv transmission in the Townsville region.