Multiple outbreaks of dengue serotype 2 in north Queensland, 2003/04

Abstract

Objectives: To describe the various investigations and responses to multiple outbreaks of dengue serotype 2 that occurred in north Queensland in 2003/04. Methods: Details about each case were collated so as to target mosquitocontrol responses including control of mosquito breeding sites, interior spraying of selected premises, and a novel ‘lure and kill’ approach using lethal ovitraps. Phylogenetic analyses were undertaken to determine the genetic relatedness of viruses isolated during the outbreaks. Results: Except for a two‐month hiatus in mid‐2003, the outbreaks continued for 16 months and included 900 confirmed cases, with three severe cases and one death. The available evidence suggests that the mosquito‐control measures were effective, but delays in recognising the outbreaks in Cairns and the Torres Strait coupled with intense mosquito breeding contributed to the extensive nature of the outbreaks. Phylogenetic analyses showed that there had been only two major outbreaks, one that spread from Cairns to Townsville, the other from the Torres Strait to Cairns; both were initiated by viraemic travellers from Papua New Guinea. Conclusions: Phylogenetic analyses were essential in understanding how the outbreaks were related to each other, and in demonstrating that dengue had not become endemic. Further innovative approaches to dengue surveillance and mosquito control in north Queensland are necessary. Implications: Dengue outbreaks have become more frequent and more severe in north Queensland in recent years, raising the possibility that dengue viruses could become endemic in the region leading to outbreaks of dengue haemorrhagic fever.

To the Editor: Spatial incidence of dengue infections in Queensland, Australia

“…There has not been any recognized locally acquired dengue in Queensland south of the city of Townsville (in the north of the state) since the mid-1950s when dengue transmission occurred in Rockhampton [2,3]. Therefore, the maps (Figures 3-5) in the paper that indicate dengue incidence, inferring local transmission of dengue south of Townsville, are not only quite incorrect but also misleading.…”

Weather-Driven Variation in Dengue Activity in Australia Examined Using a Process-Based Modeling Approach

“…22 However, dengue outbreaks are largely restricted to major population centers such as Cairns and Townsville, where they have occurred almost annually in the past 15 years. 19 Dengue outbreaks did not occur in Australia during 1955-1981, 23 but were previously widespread in eastern Australia, from northern New South Wales to northern Queensland. 24 Since 1990, regular outbreaks have occurred, including outbreaks with up to 1,000 reported cases.…”

“…24 Since 1990, regular outbreaks have occurred, including outbreaks with up to 1,000 reported cases. 19,25,26 There is concern that the geographic range and magnitude of outbreaks may increase in Australia as the climate changes. 27 The World Health Organization recommends estimating the future burden of disease attributable to climate change by quantifying current climate-disease relationships and making statistical projections under future climate scenarios.…”

“…5,[16][17][18] Dengue is not endemic to Australia; in far northern Queensland, the only area where dengue occurs, transmission is greatly reduced or absent during the dry season. 19 Viremic travelers from dengue-endemic regions, especially Southeast Asia, are the source of frequent introductions. [19][20][21] Because Ae.…”

“…19 Viremic travelers from dengue-endemic regions, especially Southeast Asia, are the source of frequent introductions. [19][20][21] Because Ae. aegypti is established across northeastern Queensland, Australia, well inside theoretical and modeled temperature limits for dengue transmission, there is potential for dengue outbreaks in this region.…”