Response to An Outbreak of Locally Transmitted Dengue in Key Largo, FL

The Florida Keys Mosquito Control District. J Am Mosq Control Assoc., 39 (4), 2023, pp. 251–257.


ABSTRACT: Seventy-two cases of locally acquired dengue were contracted by residents and visitors of Key Largo, FL, in 2020. The primary vector, Aedes aegypti, has been a large focus of the Florida Keys Mosquito Control District’s (FKMCD) control measures for over a decade. This paper recounts the 2020 outbreak of DENV in Key Largo, FL, and the FKMCD’s Ae. aegypti operational response. The overall House Index (13.43%) during the outbreak was considered high (>5%) risk for local transmission. Larval habitat characterized from property inspections was similar to previous larval and pupal habitat studies. Adult surveillance of the active dengue transmission area provided 3 positive pools out of 1,518 mosquitoes tested resulting in a minimum infection rate of 1.976. Increased personnel response with long-term larvicide formulations and increased aerial, truck, and handheld ultra-low-volume adulticide control measures quickly reduced the Ae. aegypti surveillance numbers below the action threshold. No active cases of dengue have been reported since October 2020.

Note: This article provides a case study of one district’s response to a local dengue outbreak. Here, two initial cases were reported on 3 Mar 2020 but subsequent suspect cases were not recognized until 17 Jun after considerable transmission. Two cases that occurred in Jan 2020 were not reported until late 2021. This cascade of events clearly shows the importance of case surveillance and reporting and fits well with our conference discussions as districts review existing response plans following California’s first two cases of locally transmitted dengue.