New research reveals dengue fever mystery in two US cities both exposed to risk

EurekAlert via the American Society of Tropical Medicine and Hygiene: As dengue fever continues to spread from Key West north into the Florida mainland, it remains a mystery as to why this dangerous mosquito-borne illness is not yet common around Tucson, Arizona—even though outbreaks routinely occur in nearby Mexico and mosquitoes that can carry dengue are now common in the state, according to a new research presented today at the annual meeting of the American Society of Tropical Medicine and Hygiene (ASTMH).

"Key West and Tucson share a lot of risk factors. Even in arid Tucson we have a large 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," said Kacey Ernst, PhD, an infectious disease epidemiologist at the University of Arizona in Tucson.

Ernst presented preliminary findings from an ongoing study she is conducting with Mary Hayden, PhD, a scientist at the National Center for Atmospheric Research (NCAR) in Boulder, Colorado, whose work focuses on the link between human behavior and climate-related health threats.

Their survey of residents in the two cities 2,000 miles apart and with different climates turned up many similarities. More than half of the respondents in both cities reported spending at least an hour outside each day. The use of central air conditioning, thought to lower the risk of dengue, was virtually identical (55% in Key West vs. 56% for Tucson), though some of the Tucson air conditioning systems are less dengue-friendly. They note that many people in the Tucson area use evaporative cooling systems or "swamp coolers," which increase the humidity in the home and may increase mosquito survivability, particularly in a desert environment.

"It is still a mystery as to why dengue infection has not shown up here," 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."...

Tucson at dusk shot by Zereshk, Wikimedia Commons, under the Creative Commons Attribution 3.0 Unported license