Jul 5, 2012
Climate changes for dengue fever in US
Rising temperatures in the US are likely to shift the risk of dengue outbreaks in the southern US from the summer to the spring and autumn. It seems that warmer conditions could shorten the lifespan of the Asian tiger mosquito (Aedes albopictus), which transmits the virus, so that it does not have time to incubate dengue before its death.
"Dengue has been described as the most important vector-borne disease in the world because there are up to 100 million infections annually and up to 40% of the world's population is threatened by the disease," Richard Erickson of Texas Tech University told environmentalresearchweb. "Climate change is expected to increase the range of the disease and number of people at risk."
Erickson and colleagues from Texas Tech and Research and Testing Laboratories, US, modelled dengue season length for three cities at the edge of the Asian tiger mosquito's US range – Atlanta, Georgia, at the south-eastern edge, Chicago, Illinois to the north and Lubbock, Texas in the west. Both Atlanta and Lubbock lie near regions where dengue is endemic. The infection can cause flu-like illness and, in severe cases, death.
"Surprisingly, we found that climate change would shift, rather than increase, the risk for dengue outbreaks within the southern United States," said Erickson. "Additionally, we found that climate will likely increase the northern range of dengue risk within the United States."
Erickson believes another take-home message is that the effects of climate change will often be nonlinear and counter-intuitive. "We must study systems if we want to understand how climate change will affect them because our intuitions and expectations may be wrong," he said.
Dengue is conventionally thought of as a tropical/sub-tropical disease that occurs in the developing world, explained Erickson. "But in recent years there have been outbreaks in the developed world (e.g. Queensland, Australia currently occurring, Key West, Florida, US in 2009 and 2010, and Hawaii, US in 2001) and locally acquired cases in non-tropical regions (e.g. France and Croatia in 2010, Texas 2005)."
Dengue is also transmitted by the yellow fever mosquito (Aedes aegypti), but this insect copes less well with cooler temperatures in more temperate regions.
In contrast to the traditional technique of looking at "climate envelopes" to study how climate change is likely to affect organisms, Erickson and colleagues used a mechanistic population model for the Asian tiger mosquito.
"We would like to take our research forward by examining how other factors will affect potential dengue outbreaks," said Erickson. "Specific factors we would like to study include precipitation, interspecific competition and socioeconomic factors. We would also like to study the potential for dengue outbreaks on a large geographic scale including more of North America and Europe."
The team reported the study in Environmental Research Letters (ERL).
About the author
Liz Kalaugher is editor of environmentalresearchweb.