Cairns records locally caught case of dengue amid global surge

Cairns has recorded its first locally acquired dengue virus infection since 2018 but the region has dodged a bullet amid a global surge in the illness.

Queensland Health reported the case on Monday. Health officials confirmed the patient was recovering at home a day later.

“We are [now] looking into how they may have become infected,” Cairns and Hinterland public health service director Jacqui Murdoch said.

The Cairns region recorded a locally acquired case of dengue fever this week.Credit: Brian Cassey

“Our team is spraying mosquitoes in the area where the patient lives, and examining whether we need to spray any other areas where the person may have visited during the infection period.”

In Australia, mosquitoes capable of transmitting dengue are found only in Queensland’s tropics.

Murdoch said the risk for further cases was low, since the region’s mosquitoes were largely unable to transmit dengue virus following intervention from the World Mosquito Program from 2011 to 2018, which targeted cities including Cairns and Townsville.

The Aedes aegypti mosquito can transmit dengue, Zika, yellow fever and Chikungunya viruses. Its population is currently limited to Queensland.Credit: James Gathany/ CDC

The program, managed out of Monash University, introduced the Wolbachia bacterium to local mosquito populations, reducing their capacity to spread dengue.

Assistant Professor Katie Anders – a researcher from the Monash School of Public Health and previously the World Mosquito Program – said the bacterium was not 100 per cent effective.

“Having one breakthrough case, or a small cluster of breakthrough cases, is still consistent with the expectations for the intervention at a population level like this,” she said.

“It’s not just binary … it’s also how much Wolbachia is there in the cells of the mosquitoes, and that is relevant for blocking the potential of viruses to slip through.”

Anders said laboratory tests showed prolonged heat exposure could dampen the bacterium’s effect, and any potential mosquito population surge after wet conditions earlier in the year would increase the likelihood of transmission.

She added that the case in Cairns came during a surge of dengue cases in neighbouring countries, further boosting chances of transmission.

“It comes as a bit of a shock after years of nothing, but this is in the context of 2024 being the biggest by far in [terms of] an epidemic year for dengue globally,” Anders said.

Global reporting from the World Health Organisation and its regional agencies recorded about 14 million confirmed cases in the Americas and South-East Asia.

The Australian Department of Health and Aged Care recorded almost 2400 cases in 2024, with Queensland making up 15 per cent – despite being the only state with dengue-carrying mosquitoes – since every instance of the illness was acquired overseas.

In 2025, 885 cases have been reported nationally, with Queensland Health recording 178.

“In the absence of Wolbachia, we would have every reason to expect to see outbreaks of the size of 2009 in Cairns, which was 1000 local cases,” Anders said.

“Instead, we’re seeing no local cases for a decade.”

Anders and Murdoch maintained precautions against mosquito-borne illnesses remained key for prevention, and many other local mosquito-borne diseases – including Ross River virus – were not blocked by the program.