Dengue is the most common vector-borne viral disease in the world, according to a report from the Centers for Disease Control and Prevention (CDC). For United States residents, dengue threatens mostly travelers to tropical areas, but local infections are on the rise. Dr. A. Trout of Rochester General Hospital, New York, and colleagues explained why the CDC is concerned.
“Cases of dengue in returning U.S. travelers have increased steadily during the past 20 years,” Trout wrote. Mosquito transmission of the virus cause an estimated 50 to 100 million infections and 25,000 death per year worldwide. Reported cases have increased fourfold since the 1980's in Mexico, Central America, South America, and the Caribbean. Rapid urbanization with mosquito breeding sites and increased international travel are contributing factors.
Travelers who return to the United States with dengue fever have the potential to introduce the virus to local mosquitoes, who can then infect others and produce an outbreak. Trout reported that seven localized outbreaks have occurred along the Texas-Mexican border since 1980.
Dengue fever struck Key West, Florida, in the fall of 2009 and sickened 28 people before the outbreak was contained. The Florida Keys Mosquito Control District responded with increased insecticide spraying, a public education campaign, and an intense door-to-door campaign to find and eliminate mosquito breeding sites.
Dengue infections cause a range of symptoms, from a mild fever to life-threatening hemorrhagic fever or dengue shock syndrome. Trout encouraged prompt diagnosis reporting of dengue to stop the spread of disease as soon as possible.
In a separate study, Judy A. Streit and colleagues at the University of Iowa found an upward trend in dengue cases among patients hospitalized in the United States. Over the study period of 2000 to 2007, an estimated 1,250 patients were hospitalized for dengue, and the annual rate tripled.
“Although infrequent, severe consequences of dengue infection may occur in returning travelers,” Streit warned. A survey of 219 patients showed that 11 percent suffered internal hemorrhage, plasma leakage, shock, and thrombocytopenia (low platelet count in the blood).
A controversial way to prevent dengue is to kill off the mosquito population with genetically modified insects. Bijal P. Trivedi reported in the November 2011 issue of Scientific American that testing is already underway for a gene mutation that kills the biting females of one species of mosquito, while leaving the males healthy enough to compete with unmodified males.
References:
1. Centers for Disease Control and Prevention, “Locally acquired dengue – Key West, Florida, 2009-2010”, MMWR Morbidity and Mortality Weekly Report 2010 May 21; 59(19): 577-81.
http://www.ncbi.nlm.nih.gov/pubmed/20489680
2. Streit JA et al, “Upward trend in dengue incidence among hospitalized patients, United States”, Emerg Infect Dis. 2011 May; 17(5): 914-16. http://www.ncbi.nlm.nih.gov/pubmed/21529411
3. Trivedi BP, “The Wipeout Gene”, Scientific American 2011 November; 305(5): 68.
http://www.scientificamerican.com/article.cfm?id=the-wipeout-gene
Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.
Reviewed November 1, 2011
by Michele Blacksberg RN
Edited by Jody Smith