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

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 mosquito-control 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 approximately 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.

A focal, rapidly-controlled outbreak of dengue fever in two suburbs in Townsville, north Queensland, 2001.

In April-May 2001 an outbreak of dengue fever occurred in two suburbs in Townsville, north Queensland. This was the first outbreak in the Townsville region since a very large outbreak in 1992-1993. Notification delays resulted in late detection of the outbreak. Once recognised, control measures were implemented and rapid control was achieved. Dengue serotype 2 was the causative virus and 9 cases of dengue fever were documented. The approach to management of dengue fever outbreaks and vector control strategies have been improved and refined in the years since the 1992-1993 outbreak. These measures, in addition to favourable weather conditions, were likely to have contributed to the successful containment of this outbreak.

Dengue in north Queensland, 2002.

In 2002 three separate outbreaks of dengue were detected in north Queensland, including the first documented outbreak of dengue 4 in Australia. Molecular analyses identified Thailand and Indonesia as the likely origin of two of the outbreaks. Investigations during 2002 also included a suspected dengue outbreak in the Torres Strait which proved to be a false alarm, and a number of imported cases of dengue in north Queensland.