49 - Mosquito-Borne Disease Surveillance in Florida

Arboviruses are of particular concern in Florida due to the state’s semi-tropical climate, potentially allowing for year-round activity. Surveillance in Florida is a concerted effort between the Florida Department of Health (FDOH) and local mosquito control programs. West Nile virus (WNV), Eastern equine encephalitis virus (EEEV), and St. Louis encephalitis virus are endemic in Florida. In addition to surveillance for equine and human cases, Florida also has a sentinel chicken surveillance program. Mosquito control programs in 26 counties submit blood samples from sentinel chicken flocks, which are tested for endemic arbovirus exposure. FDOH generally screens at least 45,000 chicken samples per year. From 2001–2022, 13,210 chickens tested positive, with WNV being the most frequently detected (69%), followed by EEEV (22%). Human cases are more commonly reported for WNV, with an average of 20 each year (range 0–93; median 12). Human EEE cases are much rarer, with less than 100 documented cases since 1957 (average 1.3 cases per year; range 0–5). Mosquito-borne illness advisories and alerts are regularly issued in response to increased activity; triggers are based on human and horse cases, sentinel chicken activity, or positive mosquito pools (not a primary surveillance method).

The state’s high volume of international travelers also increases risk for introduction of exotic arboviruses, such as dengue, chikungunya, and Zika viruses. Dengue is the most common, with travel-related cases reported each year since 2009 (range 19–929; median 86), and at least one locally acquired case reported in Florida almost annually (range 0–77; median 7). As humans are the virus reservoir, surveillance activities focus on identifying human cases, so that rapid mosquito control activities can occur to prevent further transmission locally. Florida’s unique environment and human population dynamics require a multifaceted approach for surveillance of both endemic and exotic arboviruses.