Climate Change Spurring Dengue Rise, Experts Say

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Mexican health officials have begun to acknowledge that climate change may be a factor in the uptick of dengue cases.

Pablo Kuri, director of the center of epidemiology, told reporters last week that he is seeking 1.8 million U.S. dollars (20 million Mexican pesos) to aid seven Mexican states with the highest incidence of dengue.

Andres Flores Montalvo is director of climate change studies at the National Institute of Ecology in Coyoacán.

"There are many factors that could explain the growth in the number of cases of dengue in Mexico, but surely increases in temperature and precipitation are influential," Flores Montalvo said.

For example, a 2006 study published by both the National Institute of Ecology and the National Institute of Public Health found an increase in the incidence of vector-transmitted diseases—such as dengue and malaria—that were associated with rising temperatures and rainfall patterns. (Related news: "Warming May Spur Extinctions, Shortages, Conflicts, World Experts Warn" [April 6, 2007].)

New Niches

One of the most notable changes is that cases of dengue are now appearing in Mexican states outside the traditional range of the dengue-carrying mosquito, including the northern state of Chihuahua. (See a map of the region.)

Horacio Riojas is the head of the environmental health unit at the National Institute of Public Health and the lead author of the 2006 National Institute of Ecology study.

The combination of higher temperatures and greater humidity is allowing the dengue mosquito to flourish in its native habitat as well as in new regions of Mexico, he said.

"The vector [mosquito] ... is generating more and better niches where it can thrive," Riojas said.

The rise in natural disasters such as hurricanes in Mexico has also indirectly contributed to the spread of dengue, Riojas added.

After Hurricane Stan hit southern Mexico in 2005, public health researchers detected changes in the hydrology of rivers caused by the hurricane's force—which created new reservoirs for the dengue mosquito to breed.

Both Riojas and Flores Montalvo agree that more research is needed to understand the relationship between dengue and climate change in Latin America.

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