Scientists have designed a new model to predict how temperatures will impact the transmission patterns of the mosquito-borne Ross River virus.

Accurately predicting how viruses will spread across different geographical regions and population centers can help governments and public health organizations strategically deploy resources.

Weather is just one of a variety of factors that can influence how a virus moves across a region and population. But as the globe gets hotter, it is important for scientists to anticipate the impacts of climate change on development of viral epidemics.

The new temperature model, designed by researchers in the U.S. and South Africa, could help health officials stay one step ahead of mosquito-borne diseases in a warmer world.

"Scientists are realizing that warmer temperatures mean longer mosquito seasons and mosquitoes entering new regions where it was previously too cold for them to survive," Erin Mordecai, an assistant professor of biology at Stanford, said in a news release. "Warm temperatures also speed up the biological processes that help mosquitoes spread viruses. But working out the precise effect of temperature on different stages of mosquito growth and spread of viruses is tricky, because so many factors are involved."

To understand the link between temperature and the movement of mosquito-borne diseases, scientists turned their attention to the Ross River virus, which infects 2,000 to 9,000 people annually in Australia and causes long-term joint pain and disability.

In the subtropical north, the virus is present year round. But during the summer, as temperatures rise across the whole of the island continent, the disease spreads to the temperate south.

To build their predictive model, scientists began in the lab. Researchers measured the impact of temperature on the behavior of two mosquito species most responsible for the spread of Ross River virus.

Previous studies have shown mosquitoes are more likely to transmit the dengue fever virus on warmer days.

The latest experiments characterized the influence of warmer temperatures on the insects' growth, survival and bite rate, as well as the infectiousness of the Ross River virus.

When they plugged their data into the model, they found it accurately predicted the seasonal spread of the Ross River virus across Australia.

"Our model correctly predicted that RRV is endemic across tropical Northern Australia year-round, and is seasonally epidemic in the cooler regions of Southern Australia," said Sadie Ryan, associate professor of medical geography at the University of Florida. "When human population data was added into the model, its prediction of seasonal patterns matched recorded human cases of RRV."

Simulations showed the ideal temperature for RRV transmission is 80 degrees Fahrenheit, while the survival and reproductive rates of virus-carrying mosquitoes are hampered by temperatures below 63 degrees Fahrenheit and above 89 degrees Fahrenheit. As the climate warms, some places are likely to experience an uptick in RRV infections, while other places will experience a decrease.

Scientists shared their new model this week in the journal eLife.

"Our study provides strong evidence that temperature drives infection patterns at the continent-wide and seasonal levels," said Marta Shocket, postdoctoral researcher at Stanford. "In the short term, our work will help researchers build better statistical models for RRV which can be used to make more specific predictions based on climate change. In the long term, it should help mosquito control agencies better plan for the future and may provide further evidence of the need to combat climate change."

Related Links
Epidemics on Earth - Bird Flu, HIV/AIDS, Ebola

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