This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Late last week Texas public health officials confirmed a new wave of dengue fever has cropped up in the southernmost tip of Texas, marking the first outbreak the state has seen since 2005. The news came on the heels of reporting in Scientific American about how scientists are trying to uncover why the mosquito-borne infection is cropping up in Florida but not in other regions of the nation that host the same Aedes aegypti species of dengue-carrying mosquitoes.
Texas public health officials announced that the same area that saw an outbreak almost a decade ago now has 18 confirmed cases of the disease. Seven are believed to have been locally acquired (rather than contracted when traveling to a dengue-endemic region), according to the Texas Department of State Health Services (DSHS). The dengue outbreak in southern Texas’s Cameron County and neighboring Hidalgo County comes after there had been an uptick in cases directly across the Texas–Mexico border in Tamaulipas over the last couple of months.
Although cases of dengue fever have occurred in the Lone Star State since 2005, they were typically imported—acquired when a traveler was bitten by an infected mosquito elsewhere in the world. The new cases announced last week mark the first actual outbreak of dengue on either side of the border. The “outbreak” classification refers to a higher than expected number of cases either in a given period of time or in a given population. “We’ve seen in Cameron County over the last several weeks more dengue cases than we would expect,” says Chris Van Deusen, a spokesman for DSHS. In the last decade Cameron County has seen 27 cases, so 14 occurrences there over the past few weeks is significantly higher than normal.
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Until recently only three dengue outbreaks had taken hold in the U.S. during the 21st century. Outbreaks occurred in Hawaii (2001); Brownsville, Texas, (2005); and southern Florida, beginning in 2009. In 2013 cases in southern Florida continue to rise, with a total of 23 reports of locally acquired dengue afflicting 21 Floridians and two out-of-state-residents living in Martin and Miami-Dade counties. Now, with the uptick in Texas cases as well, scientists are reexamining how, or if, it’s possible to “harden” locations that host significant populations of dengue-carrying mosquitoes against outbreaks beyond telling people to beware of standing water and to wear long sleeves.
Although dengue symptoms, when mild, can seem flulike, there is no vaccine or treatment for the infection other than staying hydrated and taking acetaminophen to manage the pain. Those flulike symptoms also hamper public health officials’ ability to track the disease, because official surveillance of occurrences is based on medical reports and patients may not seek care for what they assume is a bout of flu. An estimated 50 million to 100 million dengue infections occur worldwide yearly, and severe forms of the disease can be fatal, especially among children. Beyond dengue’s death toll, its impact is largely felt in economic terms because sickened people cannot work or attend school.