Academic journal article Environmental Health Perspectives

Climate Variation and Incidence of Ross River Virus in Cairns, Australia: A Time-Series Analysis. (Articles)

Academic journal article Environmental Health Perspectives

Climate Variation and Incidence of Ross River Virus in Cairns, Australia: A Time-Series Analysis. (Articles)

Article excerpt

In this study we assessed the impact of climate variability on the Ross River virus (RRv) transmission and validated an epidemic-forecasting model in Cairns, Australia. Data on the RRv cases recorded between 1985 and 1996 were obtained from the Queensland Department of Health. Climate and population data were supplied by the Australian Bureau of Meteorology and the Australian Bureau of Statistics, respectively. The cross-correlation function (CCF) showed that maximum temperature in the current month and rainfall and relative humidity at a lag of 2 months were positively and significantly associated with the monthly incidence of RRv, whereas relative humidity at a lag of 5 months was inversely associated with the RRv transmission. We developed autoregressive integrated moving average (ARIMA) models on the data collected between 1985 to 1994, and then validated the models using the data collected between 1995 and 1996. The results show that the relative humidity at a lag of 5 months (p < 0.001) and the rainfall at a lag of 2 months (p < 0.05) appeared to play significant roles in the transmission of RRv disease in Cairns. Furthermore, the regressive forecast curves were consistent with the pattern of actual values. Key words: autoregressive integrated moving average, climate change, cross-correlation function, disease prediction, Ross River virus. Environ Health Perspect 109:1271-1273 (2001). [Online 28 November 2001]

http://ehpnet1.niehs.nih.gov/docs/2001/ 109p1271-1273tong/abstract.html

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Ross River virus (RRv) is the most common and widespread arbovirus infection in Australia (1,2). It was first identified as epidemic polyarthritis in the Murrumbidgee River area of New South Wales, Australia, in 1928 (3). The causative agent was recognized as a mosquito-borne arbovirus in 1960 (4). A virus was isolated from a pool of Aedes vigilax mosquitoes collected around Ross River near Townsville in 1963 after which the virus was named (5).

RRv is characterized by arthritis, rash, and constitutional symptoms such as fever, fatigue, and myalgia (2,6). In most years, RRv is recorded as geographically scattered cases throughout the year, but with the preponderance of cases occurring from January to May, particularly in the tropics (7).

For the years 1991-2000, 53,347 laboratory-confirmed cases of RRv infection were reported (8). Numerous studies have examined the relationship between climate variation and arboviral disease (9-12). Several models have been developed to assess the potential impact of such future climatic changes on health (10). The incidence of RRv has been linked to climatic factors, particularly rainfall, high tide, and temperature (11,12). However, the quantitative relationship between climate variation and the transmission of arboviruses remains to be determined.

Time-series methodology has a long history of application in econometrics, particularly in forecasting. Recently it has been used extensively to study the effects of environmental exposures (e.g., air pollution on mortality and morbidity) (13-17).

Autoregression integrated moving average (ARIMA) models are a useful tool for analyzing nonstationary time-series data containing ordinary or seasonal trends (17,18). Because most of climate-sensitive diseases have seasonal patterns, ARIMA models may be suitable for this type of data.

In this study we aimed to examine the potential impact of climate variability on the transmission of RRv infection using the ARIMA transfer function and to assess the potential predictors of the RRv incidence.

Materials and Methods

Cairns is the main coastal city of north Queensland in Australia (Figure 1). Its population was 49,332 on 31 December 1999. It is about 1,600 km from Brisbane, capital of Queensland (19). Cairns is also a major tourist city, and the transmission of RRv has a considerable impact on tourism there. …

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