Academic journal article Environmental Health Perspectives

Spatial Patterns and Socioecological Drivers of Dengue Fever Transmission in Queensland, Australia

Academic journal article Environmental Health Perspectives

Spatial Patterns and Socioecological Drivers of Dengue Fever Transmission in Queensland, Australia

Article excerpt

BACKGROUND: Understanding how socioecological factors affect the transmission of dengue fever (DF) may help to develop an early warning system of DF.

OBJEcTIvEs: We examined the impact of socioecological factors on the transmission of DF and assessed potential predictors of locally acquired and overseas-acquired cases of DF in Queensland, Australia.

METHODS: We obtained data from Queensland Health on the numbers of notified DF cases by local government area (LGA) in Queensland for the period 1 January 2002 through 31 December 2005. Data on weather and the socioeconomic index were obtained from the Australian Bureau of Meteorology and the Australian Bureau of Statistics, respectively. A Bayesian spatial conditional autoregressive model was fitted at the LGA level to quantify the relationship between DF and socioecological factors.

RESULTS: Our estimates suggest an increase in locally acquired DF of 6% [95% credible interval (CI): 2%, 11%] and 61% (95% CI: 2%, 241%) in association with a 1-mm increase in average monthly rainfall and a 1 [degrees] C increase in average monthly maximum temperature between 2002 and 2005, respectively. By contrast, overseas-acquired DF cases increased by 1% (95% CI: 0%, 3%) and by 1% (95% CI: 0%, 2%) in association with a 1-mm increase in average monthly rainfall and a 1-unit increase in average Socioeconomic index, respectively.

CONCLUSIONS: Socioecological factors appear to influence the transmission of DF in Queensland, but the drivers of locally acquired and overseas-acquired DF may differ. DF risk is spatially clustered with different patterns for locally acquired and overseas-acquired cases.

KEY WORDS: Bayesian spatial analysis, dengue, socioecological factors. Environ Health Perspect 120:260-266 (2012). http://dx.doi.org/10.1289/ehp.1003270 [Online 20 October 2011]

Dengue fever (DF) is one of the most prevalent arboviral diseases in the world, and its global range of transmission has increased significantly in recent decades (Phillips 2008). Secondary DF infection with a serotype of dengue virus different from that of the primary infection commonly results in the more serious dengue hemorrhagic fever (Gubler 1998). The large-scale reemergence of DF during the past few decades has renewed the status of DF as a serious international public health problem, especially in tropical and subtropical areas, including Australia (Gubler 1998; Rogers cc 2006). Over the past 17 years (1993-2009), 6,271 laboratory-confirmed DF cases have been reported to the Australian Department of Health and Ageing (2010). Major outbreaks have occurred in northern Queensland, centered in Cairns, Townsville, and the Torres Strait islands (Hanna et al. 1998, 2001; Tropical Public Health Unit Network 2004). Although DF is not naturally endemic in Australia, the dengue vecror--Aedes aegypti--inhabits northern Queensland. and outbreaks can occur when the virus is introduced to the local mosquito population by infected international travelers and migrants or residents who were infected while traveling overseas Tropical Public Health Unit Network 2004). The recent arrival of the exotic species--Aedes albopictus--into Australia is of greater concern for southern Australia (Russell 2009). If Ae. albopictus becomes colonized on the mainland, it could very likely extend to all the southern states (Russell et al. 2005), broadening the potential geographical range of dengue transmission in Australia. Currently, no antidengue drugs are available, and no effective vaccine is available for DF (Edelman 2005).

Weather conditions directly affect the breeding, survival, and abundance of mosquitoes (Hales et al. 2002). The ideal temperature range for transmission of DF is 18-33.2[degrees] C, with female mosquitoes feeding more frequently when temperatures are higher (Depradine and Lovell 2004; Nagao er al. 2003). Some studies show that meteorological variables (e.g., rainfall, temperature, and relative humidity) are important climatic factors that could influence the risk of DF outbreaks (Depradine and Lovell 2004; Diallo et at 2003). …

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