Two contiguous outbreaks of dengue type 2 in north Queensland

Abstract

Objectives: To investigate two outbreaks of dengue type 2 in north Queensland, one in the Torres Strait beginning in late 1996, the other in a Cairns suburb in early 1997. Design: Epidemiological investigation of all laboratory‐confirmed cases of dengue, entomological investigation of the local environment, and laboratory analysis of the isolated dengue viruses. Main outcome measures: Numbers of confirmed and of locally acquired cases; virus serotype; comparison of nucleotide sequences between viruses isolated from the two outbreaks; and Breteau Index (Bl = number of containers with larvae of the mosquito vector Aedes aegypti found per 100 houses investigated) on the affected islands and in the Cairns suburb. Results: There were 201 confirmed cases of dengue in the Torres Strait outbreak, which lasted nearly seven months, and seven confirmed cases in the Cairns outbreak, which lasted about nearly 11 weeks. Most (190) were confirmed as dengue type 2. Nucleotide sequencing of viruses isolated from the two outbreaks showed they were identical. Ae. aegypti breeding sites were very common on the five Torres Strait islands surveyed (Bis, 73‐219 ‐ high risk), but less so in the Cairns suburb (Bl, 23). The most common breeding sites were water storage reservoirs, particularly rainwater tanks, on the outer Torres Strait islands, discarded containers (such as plastic containers, buckets and tyres) on Thursday Island, and garden items (such as flowerpot bases and jars) in Cairns. Conclusions: The virus responsible for the Cairns outbreak was most probably introduced from the Torres Strait, whereas the virus responsible for the Torres Strait outbreak was imported from Papua New Guinea. Preventive strategies tailored to specific locations are needed to reduce breeding of Ae. aegypti in north Queensland, and the consequent risk of future outbreaks of dengue.

A spatial simulation model for dengue virus infection in urban areas

“…aegypti blood feeding and ii) human-made breeding habitats such as rainwater tanks, underground sumps, flower pots etc. [36]. Previous studies have shown significant correlations between vegetation cover and the abundance of Ae.…”

Water quality and public health risks associated with roof rainwater harvesting systems for potable supply: Review and perspectives

“…Rainwater tanks are potential breeding site for the dengue virus vectors and therefore it is recommended they be screened (WHO, 1997). Hanna et al (1998) reported an outbreak of Dengue in the Torres Straits Islands in 1996-1997 while a survey by Ritchie et al (2002) conducted in the same islands, and revealed that the adult mosquitos were present in rainwater tanks that had no screens or had damaged screens.…”

Novel Estimates ofAedes aegypti(Diptera: Culicidae) Population Size and Adult Survival Based onWolbachiaReleases

“…However, container and pupal surveys are laborious, and often miss so-called cryptic breeding sites that are hard to locate and difÞcult to access. This includes subterranean containers such as sump pits (Montgomery et al 2004) and telecommunication pits (Kay et al 2000), and elevated sites such as roof gutters (Montgomery and Ritchie 2002) and rainwater tanks (Hanna et al 1998), all of which can be highly productive key containers within their locale.…”