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Florida Medical Entomology Laboratory

Florida Medical Entomology Laboratory

Dengue in Key West? Florida's Dirty Little Secret?

On July 23, 2010 “Dengue Fever? What About It, Key West Says” appeared in the New York Times ( The article illustrates the dilemma facing Florida Keys Mosquito Control District (FKMCD) and the Monroe County Health Department (MCHD) in combating the Key West dengue outbreak. The article states that tourists have asked about false rumors that Key West is being evacuated due to dengue and there have been concerns that information about the outbreak provided by the U. S. Centers for Disease Control (CDC Health Advisory 000315) are alarmist that could adversely influence tourism that is vital to the local economy. A July 24, 2010 St. Petersburg Times article “Officials say there is no dengue fever epidemic in Key West” ( states that business leaders are unsettled by the way CDC has publicized the dengue cases in Key West. Why the confusion?

Fig. 1 Ant guards on plants at the old Ancon Hospital,
Panama. From: Le Prince, Joseph A. 1916. Mosquito control in
Panama: the eradication of malaria and yellow fever in Cuba
and Panama. New York: G.P. Putnam's Sons.

Elsewhere (Tabachnick, WJ. 2010. Florida’s third rail: Declaration of a Medical Illness Threat, BuzzWords 10(2):10-11) the possibility was raised that decisions concerning protecting the public against dengue may be influenced by concerns about the impact on the tourist economy. The news articles unfortunately validate that there is tension between providing warnings to the public about precautions needed to reduce transmission and risk, yet avoid alarming the public to protect tourism so vital to the economy.

The FKMCD continues mosquito control against Aedes aegypti using all available means at its disposal. This has included public service announcements also being provided through MCHD, home visitations to provide information to reduce risk and to eliminate Ae. aegypti larval habitats, adulticiding, larviciding and setting out thousands of lethal oviptraps to kill egg laying Ae. aegypti. The efforts are prodigious and require a substantial amount of the FKMCD’s funds. Aedes aegypti control is a very tall order. Unfortunately the public may believe that Florida mosquito control, so effective controlling other Florida mosquito pests, will also control Ae. aegypti in Key West thereby stopping dengue. However, unlike the Florida mosquitoes that FKMCD is so effective against, Ae. aegypti resides inside buildings, use artificial human water storage containers for larval development, bites 24/7 and prefers humans as hosts, resulting in reduced effectiveness of many of mosquito control’s successful tactics. The massive number of yellow fever cases during the French effort to build a Panama canal in the latter part of the 19th century were in part the result of the numerous larval habitats for Ae. aegypti created by the French themselves. Fig. 1 shows the water pots surrounding trees to discourage climbing ants at the French built hospital treating yellow fever in Panama. The pots were later removed by U. S. sanitation workers who knew yellow fever was transmitted by Ae. aegypti inhabiting such containers. What if the hospital had refused to change this practice? It is long established that successful Ae. aegypti control demands an aggressive community-based approach that enlists homeowners and businesses to avoid mosquitoes, to protect themselves and their families, and to eliminate larval habitats.

The Key West dengue outbreak of 2009-2010 has, so far, been confined to only the Old Town section (est.

Fig 2. "If I had a world of my own, everything would be
nonsense. Nothing would be what it is, because
everything would be what it isn't. And contrary wise,
what is, it wouldn't be. And what it wouldn't be, it
would. You see? — The Mad Hatter"

population 6000) of Key West. The CDC and the MCHD are both right and wrong in their interpretations of the CDC serosurvey. The CDC serosurvey shows about 5% of the targeted population had a recent dengue infection in 2009. The MCHD is correct that the number of people infected is not 1000. CDC used the population size of Key West of 20,000 when the samples were obtained only from Old Town residents. Using the correct population size of Old Town, provides an estimated 300 dengue infections, not 1000. Should this smaller number give cause for complacency? The incidence of dengue infection in Old Town in 2009 was roughly 50/1000, the incidence of actual cases was about 4/1000. This incidence, though likely inflated by about 20% since a portion of the cases are tourists, is commensurate with dengue epidemics elsewhere in the world and would result in approximately 100,000 dengue infections and 8000 cases in Miami-Dade County in the unlikely event of equal exposure in the region! As of July 30, 2010 the incidence of actual cases of dengue in Old Town was already 4/1000! Based on the CDC serosurvey about 600 people or 1 in 10 Key West residents have been infected with dengue serotype 1 in 2009- 2010 creating for a more dangerous situation should a different serotype enter!

Has everything possible been done in Key West to provide residents and tourists with correct information and correct recommendations to protect themselves, their families and their neighbors for dengue? I mentioned the efforts of the FKMCD which continued efforts to reduce mosquito populations while providing information to the public. What of other efforts? The media articles report statements from Key West residents that the CDC report of infections was very alarmist, and articles have reported a “so what” attitude in Key West about dengue.

Are the mixed messages about the Key West dengue epidemic (here defined as the occurrence of more cases of a disease than would be expected in a community or region during a given time period) confusing the public? News articles claim that some have not heard about dengue, some in Key West maintain the low number of cases is no cause for concern, some describe dengue as flu-like of little concern, and some in Key West are reluctant to discuss dengue openly for fear of negative reactions and negative effects on tourism. Has this become the Mad Hatter’s Tea Party (Fig. 2)? How have messages been provided? How have the messages been received? Have messages about dengue had an impact on transmission? The New York Times reported that tourists at the nightly sunset celebration on Mallory Square were oblivious to dengue. One tourist from Pennsylvania had a fresh mosquito bite on his forearm and said “We haven’t heard anything about it. We are having a wonderful time.” Thus despite the efforts by FKMCD, MCDH, announcements, health department advisory’s and even national and local news articles, many in Key West are still unaware of precautions they can take to protect themselves from dengue and have a wonderful safe time in Key West.

More aggressive dissemination of information that will assist in fighting the outbreak should be considered. Have there been headlines in the newspaper? Have there been prominently displayed MCHD posters or flyers? Are businesses in Key West being advised directly about the things they need to do to reduce public fears and the risk of dengue? Why not display posters, like those displayed in other regions all over the world about dengue (Fig. 3), for example in Mallory Square, as another means to alert everyone about precautions? What about

Fig. 3. Posters used to alert the public to take precautions
to avoid mosquitoes and dengue. Far right
a dengue poster on the FKMCD web site.

providing certificates to stores and hotels who voluntarily request it declaring the premise is participating in the anti-dengue campaign as a result of an inspection by the MCHD and FKMCD (click for sample)? What about a bounty on mosquitoes for a week where citizens are compensated for bringing in an adult Ae. aegypti, i.e. $0.5, $1, $10 per adult? Such novel initiatives are positive ways to enlist the public and business community in a campaign that would assist the fight. A friend visiting Key West last week reported that he saw no attention on the part of businesses in suppressing Ae. aegypti and larval habitats on their premises, and an obvious reluctance to even discuss it. The Key West community can continue dismissing the outbreak, not change practices like having doors and windows open, not encourage or provide people with personal protection, not actively assist in reducing mosquitoes, and rely entirely on FKMCD to single-handedly control Ae. aegypti.

The dengue cycle can only be broken if everyone in Key West takes responsibility to provide personal protection and to reduce mosquito larval habitats thereby reducing exposure to mosquitoes. This can be done by conveying the simple things that they can do so they can continue to enjoy Key West. Community complacency will only result in greater problems this summer with more cases likely despite the heroic efforts of FKMCD and MCHD. Can I visit and enjoy Key West and not risk dengue? Consider that Key West Fantasy Fest has about 100,000 in attendance each October. An incidence then of 4/1000 would produce 400 dengue cases and 5000 dengue infections. Key West must instill public confidence to ensure that the public will believe that Key West has provided real protection through precautions to avoid mosquitoes and steps that result in few Ae. aegypti.

On July 22, 2010 CNN reported about the experiences of two Key West dengue cases ( Their stories dispute anyone dismissing dengue as mild and flu-like, and concludes with this chilling statement by one of the cases who had visited Key West where she became infected: "I will never go to Key West again, certainly," she says "no way." An unfortunate view but based on her harrowing experience. Would anyone make a similar claim from a bout of food poisoning about a city? We can do a better job conveying information to serve and protect the public. Correct, factual, widely disseminated information to increase awareness that elicits appropriate, protective public involvement is essential. I apologize for any misperceptions I may have conveyed based on the news reports. I encourage my colleagues, especially in the MCHD and/or the Florida Department of Health, to correct any inaccuracies in the next issue of BuzzWords.

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