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Booming mosquito populations and biblical bat deaths: what to expect for Australia’s increasingly hot summers

Media release: 9 December 2020.

Increasingly frequent extreme weather events due to climate change are throwing up some unexpected health challenges, exemplified by two papers published in a new issue of the journal Public Health Research & Practice.

In one paper in the Sax Institute’s peer-reviewed journal, Dr Cameron Webb, Associate Professor of Medical Entomology at NSW Health Pathology, reports on a “dramatic increase” in mosquito populations last summer, and how extreme weather and other disruptive events are impacting our exposure to mosquito-borne disease.

Following an exceptionally wet four-day period in February this year, mosquitoes increased from hundreds to tens of thousands at local surveillance locations in NSW. This meant that as the COVID-19 crisis unfolded and health resources were stretched, NSW was also experiencing higher than normal rates of Ross River virus infections.

Adaptive responses across Australia will be needed to reduce mosquito-related disease risk during natural disasters and public health emergencies, Dr Webb says.

“With the return of the La Niña weather pattern, we’re likely to see wetter conditions in many parts of the country this summer. And we know that the amount of rainfall each summer is a key predictor for seasonal outbreaks of mosquito-borne disease, especially Ross River virus.

Another paper in this issue looks at an event of mass bat deaths due to extreme heatwave conditions. This took place in Far North Queensland in 2018 and involved many thousands of the endangered spectacled flying fox.

The public health threat of mass bat deaths lies in the increased risk of disease transmission from bats to humans, in particular the Australian bat lyssavirus, as people try to rescue unwell bats or remove the remains of dead ones. The Queensland bat die-off saw a significant increase in emergency department presentations of people injured while handling bats, who were treated with a vaccine and human rabies immunoglobulin.

The event and associated public health issues were unprecedented, resulting in large numbers of worried people presenting to the hospital and clinics for vaccination. Decaying bat corpses meant that some residents vacated their premises while others assisted in the clean-up operation. Inexperienced volunteers assisting with sick or deceased bats without proper protective clothing led to further exposure risks.

The study authors say that overall, the public health and council responses were effective, given the scale of the event, but there is always room for improvement. The need for a “one health” and climate-ready approach was highlighted by this event, they say. 

“With extreme heatwaves predicted to become increasingly common in Australia, this will not be the first time we see bats dying in biblical proportions. Climate change will likely bring new public health challenges and we need to recognise that humans, animals, ecosystems and environments are inextricably linked,” says lead author Dr Lea Merone of the Tropical Public Health Service in Cairns.

In an editorial for this issue, Guest Editors Dr Jean-Frédéric Levesque, Chief Executive of the NSW Agency for Clinical Innovation, and Professor Mark Harris, Executive Director of the Centre for Primary Health Care and Equity at UNSW Sydney, write:

“Both of these papers (and of course the probable origin of Sars-CoV-2 itself) illustrate the increasing impact of humans on the natural environment and the need for a multisectoral ‘one health approach’ to addressing zoonotic diseases.”

Other papers in this issue find:

Click here to view the full contents of the latest issue of Public Health Research & Practice. Note that links will be live from 0001HRS Wednesday 9 December 2020 (AEST). Please contact us (details below) if you would like to access the papers before this date.


Hugo Wilcken, Media Manager, Sax Institute
M: 0451 122 146    E: [email protected]

Nyssa Skilton, PHRP Editor
M: 0408 331 262    E: [email protected]

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Please acknowledge Public Health Research & Practice as the source for any stories on our papers.


The Sax Institute is an independent, not-for-profit organisation that improves health and wellbeing by driving better use of evidence in policies, programs and services.