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Dengue in Key West: The Perfect Storm

Sadly, despite the efforts of the Florida Keys Mosquito Control District (FKMCD), dengue transmission continued throughout the summer of 2010 in Key West. As of September 27, 2010 there were 44 reported dengue cases in Key West, 35 of which were in Key West residents. Previously I used results from a CDC serosurvey that estimated 5% of Key West’s residents had been infected with DENV in 2009 to project that approximately 2000 people have now been infected with DENV in Key West (Tabachnick, WJ. 2010. Dengue in Key West? Florida’s dirty little secret? BuzzWords, Newsletter of the Florida Mosquito Control Association 10(3):15- 18). The incidence of dengue cases in Old Town Key West was 35/6000 or 5.8/1000 as of Sept 27, 2010 with a weekly case number during the summer of about 2-4 resulting in a weekly incidence of 0.33-0.66/1000.

How has Key West fared compared to other regions of the world reporting dengue transmission in 2010? Puerto Rico reported record levels of dengue transmission during 2010 in a population of about 4.4 million. Puerto Rico declared a public health emergency due to dengue on September 8, 2010. As of September 10, 2010 Puerto Rico had a total 12,000 suspected cases with 6139 laboratory confirmed cases. The incidence of confirmed cases in Puerto Rico was 1.4/1000 and the weekly incidence during the summer was approximately 0.09/1000. The risk for dengue was 4 to 5 times higher in Key West then in Puerto Rico! The residents of Puerto Rico were under a declared public health emergency due to dengue! With 1 in 10 Key West residents infected with DENV-1, there is now a very real potential for more severe dengue infection and dengue-related fatalities (dengue hemorrhagic fever and dengue shock syndrome) in Key West if a second dengue virus serotype becomes established on the island.

We must determine why dengue transmission could not be stopped during two successive years of transmission in a small section of an 8 square mile island that has one of the best mosquito control districts in the world. The FKMCD launched an aggressive anti-Aedes aegypti campaign by adulticiding, larviciding, the use of lethal ovitraps, periodic door-to-door sweeps throughout Key West, the distribution of brochures, contacting and educating local homeowners and businesses, and visiting schools and community organizations. Why has dengue transmission continued in Key West? Can a city, state, or a nation effectively control Aedes aegypti and stop dengue transmission in a town? Part of a town? A block or two? A few square miles?

I submit that the Key West dengue epidemic could have been stopped in 2010 with the active participation of the public in control efforts. The FKMCD clearly responded appropriately and aggressively, providing the best possible mosquito control efforts, including the most recent new mosquito control strategies. Prior to the 2009/2010 epidemic, if one asked me what region of the U.S. had the best resources to mitigate an Aedes aegypti borne dengue epidemic, Key West would have been at the top of anyone’s list. The FKMCD is a top flight mosquito control organization, well trained, experienced personnel, good resources, and experienced in Aedes aegypti control. However I would not have taken into account other considerations that I now know trumps the FKMCD’s capabilities and the capabilities of any mosquito control organization.

The reason for the continued dengue transmission in Key West, despite FKMCD, is that the Key West environment has so far provided “the perfect storm” for dengue transmission. The components of this storm are outlined below and each individual component would be an impediment to effective dengue control anywhere in the world. However, when combined, this perfect storm makes effective mosquito control for dengue intervention impossible.

What are the components of Key West’s perfect storm resulting in continued dengue transmission?

  1. A mosquito control organization beset by accusations that dengue is being used to support budgetary requests.
  2. A media where editorials and articles appear that chastised mosquito control for inefficiency while at the same time conveying dengue is purely mosquito control’s responsibility.
  3. A business community that did not participate in the anti-Aedes aegypti campaign, did not change any practices to reduce Aedes aegypti, and did nothing to enlist the public in the fight against dengue and Aedes aegypti.

FKMCD is caught in a catch-22, after the Joseph Heller book of this name. Recall that the main character Yossarian wants to be released from flying bombing missions during WWII. The famous classic exchange with Doc Daneeka from the movie Catch- 22 was:

Yossarian: “Ok, let me see if I’ve got this straight. In order to be grounded, I’ve got to be crazy. And I must be crazy to keep flying. But if I ask to be grounded, that means I’m not crazy anymore, and I have to keep flying.”
Doc Daneeka: “You got it, that’s Catch-22.”
Yossarian: “Whoo… That’s some catch, that Catch-22.
Doc Daneeka: It’s the best there is.”

FKMCD urges community participation to control dengue in Key West. However, in doing so FKMCD is subjected to accusations that there is little danger and they are only doing this to influence the mosquito control budget. Then they are being accused of not being effective in controlling the epidemic. “Whoo…That’s some catch, that Catch- 22.”

What has been the result of this perfect storm? The Key West community as a whole has done little to actively reduce Aedes aegypti numbers during the epidemic. Rather than urging public participation in eliminating Aedes aegypti larval sites, many in the community continued to ignore the seriousness of the outbreak, criticized mosquito control efforts and motives, yet relied solely on FKMCD to eliminate Aedes aegypti and dengue from the island. The community has largely ignored assisting mosquito control. Several people who have independently visited Key West this past summer commented to me that it was very apparent that businesses in Old Town were in a ““don’t ask and don’t talk” about dengue mode.

Certainly one should ask hard questions about this situation. What is the reason for the Key West attitude that has resulted in many in the community trying to play down the dengue epidemic? Who has contributed to this environment? What efforts that may have enlisted public mosquito control participation were not taken? Why? Why have the Key West papers, editorials, letters, and media been so silent on public participation? Has the local Health Department enlisted public participation and provided leadership? Does a single individual have the right to produce large numbers of dangerous Aedes aegypti on their private property? Why can individuals knowingly contribute to dengue transmission by continuing to produce the mosquito vector in their backyard? Why has there been no action? Why has there been no public peer pressure to reduce Aedes aegypti breeding sites throughout the island, especially in Old Town? Lacking homeowner and community assistance in  backyard cleanup seenoand container removal to complement effective, efficient, and environmentally sound mosquito control, there is little hope of interrupting dengue transmission. The only way to control Aedes aegypti in a setting like Key West is through aggressive and continued community involvement.

These are important questions that address why dengue transmission has continued in Key West for the past two years. Florida mosquito control districts now have the additional challenge of avoiding “the perfect storm” for a variety of vectorborne diseases in their own communities. I urge all Florida mosquito control districts to reflect on these questions and ask how they might overcome or avoid a “perfect storm.”

wjtWalter J. Tabachnick, Ph.D.
Florida Medical Entomology Laboratory
Professor, Department of Entomology and Nematology
University of Florida, IFAS, Vero Beach, FL