News

Dengue fever epidemic hits northern Australia

BMJ 2009; 338 doi: http://dx.doi.org/10.1136/bmj.b967 (Published 09 March 2009) Cite this as: BMJ 2009;338:b967
  1. Jane McCredie
  1. 1Sydney

    Authorities in northern Queensland have mounted a major public health and vector control campaign after the country’s first death related to dengue fever since 2004 was confirmed on 4 March.

    More than 650 cases of the mosquito borne disease have been confirmed in the area since December, whereas in previous recent episodes 500 or so cases had been spread over more than a year, and this is the first time in Australia that all four serotypes have been found circulating simultaneously.

    The largest outbreak, of type 3 dengue, is centred on the tourist town of Cairns, where one patient is confirmed to have died after contracting the disease and several others have developed its more serious form, dengue haemorrhagic fever. Although the fatality was an elderly woman with several comorbidities, authorities said that dengue fever was likely to have contributed to her death.

    Jeffrey Hanna, a public health physician from Queensland’s health department, said it was impossible to predict the future course of the epidemic.

    “Clearly one of our concerns here is that this is proving so difficult to control,” said Dr Hanna, “and it does raise the possibility that this could become an endemic dengue 3 virus.”

    The virus seems to have spread more quickly than in previous outbreaks, said Dr Hanna, and with a shorter extrinsic incubation period.

    John McBride, an infectious disease specialist and clinical microbiologist, said that the virus had arrived in Cairns at the start of the monsoon season, when breeding conditions for its vector, the Aedes aegypti mosquito, were ideal. The epidemic’s “unrelenting march” through the tropical north was far from over, said Professor McBride.

    “I expect it will run for another four to six weeks at least,” he said.

    The presence of several serotypes is concerning authorities, as exposure to one type gives immunity against that type only, and the risk of dengue haemorrhagic fever is greater in a secondary dengue infection. Thousands of Queenslanders had now had dengue fever at some point and were therefore at higher risk, said Dr Hanna.

    A number of candidate vaccines are being developed, but no proven antiviral treatment for dengue fever exists, and management is limited to rehydration, non-aspirin analgesia, and close monitoring of vital signs, combined with public health measures to reduce mosquito habitats and transmission of the disease.

    More travel between Australia and South East Asian countries, where dengue fever is a major public health issue, makes it inevitable that Australia will see more outbreaks of the disease, experts say.

    Some have also suggested that climate change could foster transmission of dengue and other tropical diseases. The Australian Medical Association has warned that a warming climate could see the dengue transmission zone extend as far south as Sydney by the end of this century.

    Notes

    Cite this as: BMJ 2009;338:b967