Abstract and Introduction
In 2016, four clusters of local mosquitoborne Zika virus transmission were identified in Miami-Dade County, Florida, USA, generating "red zones" (areas into which pregnant women were advised against traveling). The Miami-Dade County Mosquito Control Division initiated intensive control activities, including property inspections, community education, and handheld sprayer applications of larvicides and adulticides. For the first time, the Mosquito Control Division used a combination of areawide ultralow-volume adulticide and low-volume larvicide spraying to effectively control Aedes aegypti mosquitoes, the primary Zika virus vector within the county. The number of mosquitoes rapidly decreased, and Zika virus transmission was interrupted within the red zones immediately after the combination of adulticide and larvicide spraying.
Zika virus (ZIKV), a flavivirus that can cause birth defects and is associated with Guillain-Barré syndrome, has rapidly spread throughout the Western Hemisphere.[1–3] The virus is spread primarily by the bite of infected Aedes aegypti mosquitoes; sexual transmission and bloodborne transmission also have been documented.[4,5] The southern United States is habitable for Ae. aegypti mosquitoes, which are predominantly an urban species. Miami-Dade County, Florida, has well-established Ae. aegypti mosquito populations and is a major travel destination (15.8 million visitors reported in 2016 [https://partners.miamiandbeaches.com/tools-and-resources/research-and-statistics]). In addition, the county has a large population of residents who routinely visit countries that had Zika outbreaks in 2016.
In January 2016, the county documented its first travel-associated case of ZIKV infection. The first cluster of local vector-transmitted cases was identified through epidemiologic investigation in the Wynwood neighborhood of Miami on July 21, 2016, and was confirmed and announced on July 29. Following Centers for Disease Control and Prevention (CDC) guidelines (https://www.cdc.gov/zika/public-health-partners/cdc-zika-interim-response-plan.html) a "red zone" or travel warning was declared for pregnant women to avoid unnecessary travel to areas within ≈1 square mile around the cluster of cases (Figure 1). Subsequent clusters were identified south of 28th Street in Miami Beach on August 19, initiating a second red zone of 1.5 square miles. On September 16, a cluster was identified north of 28th Street in Miami Beach, expanding the second red zone by another 1.5 square miles to the north. On October 13, a fourth cluster was identified, and a red zone was declared in the Little River area of Miami, although all but 1 case occurred before October 13.
Locations of declared zones where clusters of locally acquired vectorborne Zika virus transmission were identified and aerial mosquito control activities conducted, Miami-Dade County, Florida, USA, 2016.
As each cluster was identified, Miami-Dade County Health Department began intensified epidemiologic surveillance to detect additional cases. Concurrently, the Miami-Dade County Mosquito Control Division (MCD) initiated intensive mosquito control activities within each new cluster of local transmission. We describe the mosquito control activities used to address the clusters of locally acquired ZIKV and their effect on subsequent mosquito numbers and Zika transmission.
Emerging Infectious Diseases. 2020;26(5):881-890. © 2020 Centers for Disease Control and Prevention (CDC)