Cases of Dengue fever, which were absent from Florida since 1934, had a resurgence throughout the summer and fall of 2009, when Key West saw 22 human cases. In 2010, 66 cases were associated with Key West, between March and November. During this time, the Florida Keys Mosquito Control District implemented the first ever aerial larviciding program using VectoBac WDG. From 2011 to 2019, the Keys only observed a total of 3 locally acquired human cases. Unfortunately, this year, in the face of a battle with COVID-19, has been the largest outbreak since 2010 with a total of 54 cases in southern Florida, 53 of which have occurred in Monroe County.

Larry Heller, a Technical Sales Representative for ADAPCO, worked with Leanne Lake, a Technical Development Specialist with Valent BioSciences, in June to ensure the Florida Keys were operationally equipped to start treatments with VectoBac WDG from their newly-acquired helicopters. They assisted the district with getting their aircraft calibrated and characterized for optimal application. Here is a video of the characterization taking place:

Dengue Outbreak in Florida

From the first case of Dengue, the Florida Keys Mosquito Control District has been vigilant with their approach. Chad Huff, from Florida Keys Mosquito Control District, has provided an excerpt about their experience this year:

For the better part of four months, the men and women of Florida Keys Mosquito Control District (FKMCD) have been fighting a war on two extremely formidable fronts: an outbreak of Dengue Fever caused by Aedes aegypti in Key Largo, FL and COVID-19 throughout all of the Keys.

Just before the threat of COVID-19 emerged, a single case of locally-acquired Dengue Fever was confirmed on the island of Key Largo in early March.

After receiving word from the state health department, FKMCD reacted quickly: our inspectors converged on Key Largo and began going door-to-door to every residence within a three block radius of the Dengue case, eliminating suspected mosquito breeding sites and educating homeowners about the potential dangers and safety precautions necessary to prevent spread. Enhanced mosquito surveillance was established in the vicinity with multiple trap locations. Based upon this surveillance, fog truck, helicopter and airplane spray missions were scheduled as necessary.

For three months, the one case of Dengue Fever remained just that: One Case.

However, in mid-June, just as FKMCD and the rest of the world’s attention became fixated on the ever growing Coronavirus Pandemic, additional cases of Dengue Fever began appearing in clusters within the same vicinity on Key Largo.

As the potential cases began to mount, FKMCD once again sprang into action. Inspectors from all across the entire 120-mile-long chain of islands that make up the Florida Keys once again converged on Key Largo. Now wearing face masks and surgical gloves, and observing all the social distancing restrictions associated with COVID-19, FKMCD inspectors began a nearly constant routine of going door-to-door, block by block, in the area around every single suspected case. By this time, crews had to contend with the sweltering temperatures and suffocating humidity associated with mid-summer in the Florida Keys.

Florida Keys go Door to Door

In addition, FKMCD Executive Director, Andrea Leal and Aerial Operations Director Josh Kogut worked with the Monroe County School District to establish a temporary helicopter landing zone (LZ) at the local school which is 40 miles closer to the ‘Dengue Zone’ than the district’s home airport in Marathon. From this makeshift LZ, FKMCD aerial and ground crews began a twice weekly series of sorties that dispersed hundreds of gallons of VectoBac WDG Biological Larvicide over the target area. Now, hours of time that would have been spent in transit is now spent over the target area with convenient and efficient reloading of the District’s new Airbus H125 helicopters taking place at the school.

florida keys mosquito control lands helicopter

Enhanced mosquito surveillance in Key Largo along with inspector observations help dictate the nearly nightly target locations for fog truck missions dispersing Fyfanon ULV as needed. The District’s twin engine Islander airplane, dispersing Dibrom has also been utilized for adulticide over the upper keys when Aedes aegypti numbers dictate.

This vigil has continued throughout the summer on Key Largo. To date, more than 50 cases of locally acquired Dengue Fever have been confirmed by the Florida Department of Health in Monroe County, but all have remained on Key Largo. The most recent mosquito surveillance in the area indicates the intense effort has resulted in a drastic drop in the number of trapped and observed Aedes aegypti but the battle continues to this day.

The amount of effort required to turn the tide in Key Largo has taken a sincere commitment from our entire FKMCD staff. Since mid-June we have logged this activity on that island alone:

  • 8,705 Inspections
  • 18 VectoBac WDG Missions
  • 70 Fog Truck Missions
  • 8 Dibrom Missions
  • 616 Traps
  • 2,718 Container Treatments
  • 12 Weeks of Sweeps
  • 15 to 40 Sweep Teams Per Week

The District’s public information office has purchased radio advertisements on several local radio stations to hammer home the message that during the rainy summer months, nearly constant prevention efforts are necessary to avoid the reemergence of this dangerous pest.

All the while FKMCD has accomplished this while maintaining consistent control efforts over highly populated Key West and the other various keys that make up the island chain.

In late summer, the influx of newly spread Dengue cases has slowed considerably, with most of the recently confirmed cases coming via antibody testing on residents who were ill in June or July.

Even now, as summer winds down, FKMCD continues the battle against the now all too familiar foes of Dengue Fever and COVID-19, more determined than ever to triumph over both.

-Chad Huff, Florida Keys Mosquito Control District

In the midst of COVID-19, the Keys have remained attentive with their treatments in order to ensure that the health of the community remains at minimal risk for Dengue fever. As you can see from above, they are working day and night to combat Aedes aegypti on the islands. Their efforts have not gone unnoticed and cases have started, and continue, to decrease since August 7th, 2020.

For a more in depth look – check out the article Battle in the Upper Keys on Public Health Landscape.

By Emily Dugas – Technical Development Specialist, ADAPCO