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When the "Dengue Fever1 in Key West" story broke last week, we were all set to regale you on the IPCC's prediction of tropical diseases expanding their range, Disney cruise lines re-routing their vessels and tourists canceling their vacations. It was a good thing other activities got in the way of blogging. As it turns out, the story gets much more interesting.
One of the concerns raised by climate change is that tropical diseases such as malaria and dengue fever will infect more people. The theory is that the altitudinal and latitudinal ranges of the vector - the mosquito - will increase as temperature rises. This in turn will bring infected mosquitoes in contact with more people and raise the incidence of disease. In 2007, it was reported "Climate change is accelerating the spread of dengue fever throughout the Americas and in tropical regions worldwide." http://news.nationalgeographic.com/news/2007/09/070921-dengue-warming.html. The science, however, since then concludes that climate change is a minor factor in the incidence of dengue and attributes more significance to population growth, urbanization, lack of sanitation, increased long-distance travel, ineffective mosquito control, and increased reporting capacity. http://www.cdc.gov/dengue/entomologyEcology/climate.html
The "Dengue Fever in Key West" story may have hit the national press last week, but it was the subject of a Department of Homeland Security "National Terror Alert" in May, http://www.nationalterroralert.com/updates/2010/05/23/dengue-fever-hits-key-west-florida/, after the CDC reported in its Morbidity and Mortality Weekly Report of an increased incidence in Key West based on cases emerging in the previous 10 months. http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5919a1.htm The CDC made no connection to climate change: "Why dengue has reemerged in Florida at this time is unknown. Dengue might have been present in the community earlier and is only now being detected. The environmental and social conditions for dengue transmission have long been present in south Florida: the potential for introduction of virus from returning travelers and visitors, the abundant presence of a competent mosquito vector, a largely nonimmune population, and sufficient opportunity for mosquitoes to bite humans."
If not new news, what precipitated the national furor? It turns out that the CDC resurrected the story with a press release in anticipation of the International Conference on Emerging Infectious Diseases held last week in Atlanta. The CDC announced: "Report Suggests Nearly 5 Percent Exposed to Dengue Virus in Key West." http://www.cdc.gov/media/pressrel/2010/r100713.htm This headline was based on the cases reported in the May report, which were then extrapolated to the Key West population, but using an inaccurate value. http://www.keysnet.com/2010/07/17/239503/cdc-errs-in-level-of-dengue-cases.html Key West authorities were upset and extracted this statement from the CDC (which was reported yesterday): "In no way, shape or form do we want to discourage people from going to Key West."
So what can we take from all this? First, while climate change may be involved in many of the changes we see around us, it may not be the significant factor in the new event. Second, the headline may not accurately state the substance of the story. As the CDC acknowledges, the conditions "have long been present" for dengue in Key West and the current detections may be reflective of ongoing but undetected dengue infections. Third, someone's ox is always gored. The CDC's paramount concern is protecting the public health. But that is tempered with its knowledge of the economic harm an epidemiological indictment of an area can cause. Public officials will not let the CDC forget that part of the equation.
And now we come back to Disney cruises and vacations. The CDC reports that the most effective way to protect against dengue fever is to avoid being bitten, which might suggest canceling a cruise or a vacation. A cautious traveler will have procured travel insurance; however, a word of caution is in order: read your cancellation coverage; not all policies cover cancellation for an epidemic or fear of an epidemic.
1Dengue or dengue fever is a tropical disease infecting globally nearly 100,000,000 people annually; 25,000 of those infections turn out to be fatal. Symptoms of dengue fever are high fever, headaches, eye pain and joint pain. Dengue is not uncommonly reported along the Texas-Mexico border. Before detection in 2009, it had not been seen in Florida since 1934.
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