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Spatial incidence of dengue infections in Queensland, Australia - reply

Published online by Cambridge University Press:  07 June 2012

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Abstract

Type
Correspondence
Copyright
Copyright © Cambridge University Press 2012

The authors reply

We appreciate the letter by Ritchie et al. as well as the extensive contribution they have made to dengue fever surveillance and control in Australia. With regard to their concern about the methodology used in our study [Reference Hu1], we respond as follows: (i) The primary objective of our paper was to examine the overall spatiotemporal pattern of notified dengue cases in Queensland over the last two decades. We stated upfront that both imported and locally acquired cases were included in data analysis and display ([Reference Hu1], p. 392]). Because the differentiation between imported and locally acquired cases has only been made in the Queensland dengue surveillance system (notifiable conditions register) since 2001, it was impossible to separate them in this 12 year time-series analysis. (ii) Our research showed a change in the spatial patterns of dengue (both imported and locally acquired) which is significant in terms of assessing dengue risk and planning resource allocation. An increase in imported cases south of Townsville is still important and it has the potential to cause dengue outbreaks because of the existence of Aedes aegypti mosquitoes in this region. (iii) Imported cases of dengue need to be monitored more closely because the number of imported dengue cases might also reflect the level of dengue transmission in endemic countries and appropriate and prompt warning should be given to travellers by the Australian government. The global geographical range of dengue has been rapidly expanding [2], and dengue fever and its vectors can cross international boundaries through international travel, migration and trade [Reference Russell3], making imported case surveillance of utmost importance. (iv) We have conducted other studies that showed a relationship between climate variability and dengue incidence (both imported and locally acquired), and there is other literature presenting concordant results [4], so the statement regarding an association between climate fluctuation and dengue transmission is supported [Reference Hu5, Reference Hu6].

Declaration of Interest

None.

References

1.Hu, W, et al. Spatial analysis of notified dengue fever infections. Epidemiology and Infection 2011; 139: 391399.CrossRefGoogle ScholarPubMed
2.World Health Organization. Dengue: call for urgent interventions for a rapidly expanding emerging disease, 2011, pp. 112 (http://www.emro.who.int/rc58/PDF/EMRC58_03en.pdf). Accessed 6 March 2012.Google Scholar
3.Russell, R, et al. Dengue and climate change in Australia: predictions for the future should incorporate knowledge from the past. Medical Journal of Australia 2009; 190: 265268.CrossRefGoogle ScholarPubMed
4.World Health Organization. Using climate to predict infectious disease outbreaks. Geneva: WHO, 2004.Google Scholar
5.Hu, W, et al. Dengue fever and El Nino/Southern Oscillation in Queensland, Australia: a time series predictive model. Occupational and Environmental Medicine 2010; 67: 307311.CrossRefGoogle Scholar
6.Hu, W, et al. Spatial patterns and socioecological drivers of dengue fever transmission in Queensland, Australia. Environmental Health Perspectives 2012; 120: 260266.CrossRefGoogle ScholarPubMed