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Dengue outbreak risk in US investigated
Researchers are studying reasons why dengue fever continues to spread from Key West, Fla., and not in Tucson, Ariz., which has an established vector population and shares similar social and behavioral characteristics with the Key West population.
"Key West and Tucson share a lot of risk factors," Kacey C. Ernst, PhD, an infectious disease epidemiologist at the University of Arizona in Tuscon, said in a press release. "Even in arid Tucson we have an established population of mosquitoes that can carry dengue, and people here spend a lot of time outdoors, but we have yet to see evidence of locally acquired infections."
Kacey C. Ernst
Ernst and colleagues presented findings from their study at the American Society of Tropical Medicine and Hygeine (ASTMH) annual meeting in Washington, D.C. The researchers compared the socioeconomic and behavioral factors associated with dengue transmission between the two cities. Household surveys were conducted in the summer of 2012, and a random sample of 400 household heads from Key West and a random cluster selection of 372 household heads from Tucson were interviewed.
Awareness of dengue infection was higher in Key West (77% vs. 57%), but use of central air conditioning was similar in both cities (55% vs. 56.2%). The Tucson population also had a similar proportion of homes with intact screens (60% vs. 55%). There was marginally greater reported outdoor activity in Key West (59% vs. 52%), with people spending at least one hour a day outdoors most days of the week. The number of people who never used insect repellent in Key West was similar to that of Tucson (46% vs. 48%). A greater number of people never checked for standing water on a daily basis in Tucson than in Key West (19% vs. 29%).
The researchers said it was possible that the dengue outbreak in Key West changed the behavior of its inhabitants, but there were few "striking differences" between the two populations.
"It's still a mystery as to why dengue infection has not shown up [in Tucson]," Ernst said. "When researchers looked at why dengue is not more common along the Texas side of the Mexico border, they cited factors limiting contact with mosquitoes, like people spending a lot of time in sealed, air conditioned buildings. Those issues are extremely important considerations, but we don’t think they fully explain why Key West has dengue and Tucson doesn't."
Ernst and colleagues are also investigating why dengue has not spread to Nogales in the Mexican border state of Sonora, a city that appears to share risks for infection similar to those of other locations in Mexico where dengue is present.
In another ongoing project, researchers from Science and Technology in Atmospheric Research and the National Center for Atmospheric Research — both located in Boulder, Colo. — are using high-resolution satellite imagery to survey locations that may be at risk for dengue outbreaks. The technology is being used to detect container habitats of Aedes aegyptimosquitoes, such as buckets or cans that collect rain water.
David H. Walker
According to ASTMH president David H. Walker, MD, these efforts represent a "full-court press" to control dengue infection from spreading.
"One of the reasons we hold an annual meeting is to allow scientists who are focusing on different aspects of the disease — the biology of the virus itself, the spread of the vector, and the role of human behavior — to share their latest findings and ultimately curtail the suffering from this disease," Walker said in a press release.
Kacey C. Ernst, PhD, can be reached at kernst@email.arizona.edu.
For more information:
Ernst KC. Abstract #LB-2150. Presented at: American Society of Tropical Medicine and Hygiene annual meeting; Nov. 13-17, 2013; Washington, D.C.
Disclosure: The researchers report no relevant financial disclosures.