September 24, 2008 | Research by NCAR scientist Mary Hayden underscores the risk of dengue fever and the growing threat of dengue hemorrhagic fever (DHF) in the Rio Grande Valley between far south Texas and northeast Mexico. Dengue fever is an acute infection caused by four dengue virus serotypes and transmitted by Aedes species mosquitoes. Any of the four serotypes can cause dengue fever; a person infected with two or more serotypes is at increased risk for the potentially fatal DHF.

Endemic to the tropics, dengue has been moving into the southern United States, perhaps due to climatic as well as human factors. Over the last several years, Mary has led a NOAA-funded study to examine how climate and human variables affect the risk of dengue fever along the U.S.–Mexico border in Arizona. In late 2005, the nation’s first-ever outbreak of DHF struck the Lower Rio Grande Valley. Shortly afterward, Mary and her colleagues surveyed households in Brownsville, Texas, and Matamoros, Mexico, and found that nearly 40% of Brownsville residents had been infected with at least one dengue serotype.

The study recommended strengthening dengue surveillance, monitoring virus strains, and providing early warning of outbreaks. It also noted practices that can help avoid mosquito infestations, including the use of repellent and the proper storage or disposal of waste tires and other objects that might capture standing water.

Mary says the next steps for the researchers are further household surveys in the region to better characterize risk by assessing indoor and outdoor mosquito populations. “We also hope to use NCAR’s High-Resolution Data Assimilation System to better understand how weather and climate relate to seasonal mosquito abundance,” she says.

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